Finlayson’s Oakworm Moth (Anisota finlaysoni): COSEWIC assessment and status report 2023

Official title: COSEWIC assessment and status report on the Finlayson’s Oakworm Moth (Anisota finlaysoni) in Canada

Committee on the status of Endangered Wildlife in Canada (COSEWIC)

Special concern

2023

COSEWIC assessment summary

Assessment Summary – December 2023

Common name

Finlayson’s Oakworm Moth

Scientific name

Anisota finlaysoni

Status

Special Concern

Reason for designation

This moth is known only from Canada and is restricted to oak habitats in southern Ontario including savannah, woodland, forest edge, and other semi-open areas. It is exposed to many threats including competition from the invasive Spongy Moth during the larval stages and the impact of Btk pesticide used to control this non-native moth. Other threats include ecosystem modification from fire suppression and the decline of oak trees.

Occurrence

Ontario

Status history

Designated Special Concern in December 2023.

COSEWIC executive summary

Finlayson’s Oakworm Moth

Anisota finlaysoni

Wildlife species description and significance

Finlayson’s Oakworm Moth (Anisota finlaysoni) is a medium-sized moth in the family Saturniidae (giant silk moths). Adults are sexually dimorphic. The male forewing length (17-20 mm) is typically smaller than the female forewing length (24-30 mm). The dorsal surface of the female wings is tawny ochreous, and the undersides are ochreous-yellow. The male wing undersides are a distinct yellow/brassy coloration. Finlayson’s Oakworm Moth is difficult to phenotypically distinguish from Orange-striped Oakworm Moth (A. senatoria).

The species has four life stages (egg, larva [with five instars], pupa and adult) and an annual life cycle. Mature larvae are approximately 50 mm in length and have a blackish-brown body with bright yellow stripes. Oakworm larvae, in general, have a pair of long horns behind the head; however, these horns are reduced to small knobs in the Finlayson’s Oakworm Moth. The short horns are considered a distinguishing feature for larval identification. Mature larvae can be identified from photographs.

Distribution

Finlayson’s Oakworm Moth has a global range restricted to southern Ontario and is considered endemic to Canada. Its historical range stretches from Rockport in the Thousand Island region, west along the north shores of Lake Ontario, south to the northeastern shore of Lake Erie, and east through the Niagara Peninsula to Fort Erie. At least 81 sites have been recorded, although its current range is now restricted to a minimum of 15 extant subpopulations in the east end of Lake Ontario and north of Lake Erie. Due to low detection and abundance, it is possible the species remains at some of its historical sites.

Habitat

Finlayson’s Oakworm Moth habitat is restricted to the Mixedwood Plains Ecozone. The species’ general habitat includes open oak woodlands, savannahs, and forests; cleared land with some natural habitat and scattered oak trees; and natural oak habitat at the edges of or adjacent to agricultural areas. Based on extant and historical observations, the species prefers open-grown oak trees, such as those found in natural oak savannahs, with a low density and abundance of shrubby vegetation. The larval host plants include White Oak (Quercus alba), Bur Oak (Q. macrocarpa), Black Oak (Q. nigra), Northern Red Oak (Q. rubra), and, to a lesser extent, Chinquapin Oak (Q. muehlenbergii). More specific ecological and plant community information is not available for the moth.

Biology

Adults fly from mid-June to mid-July. Eggs are laid in clusters on the underside of oak leaves. Young larvae are highly gregarious, and through successive moults, the late-stage older larvae disperse and become more solitary. Larvae mature in late August-September and spend the winter as pupae in the soil until the following June. The species has one generation per year.

Population sizes and trends

The size of the Canadian population of Finlayson’s Oakworm Moth, and the abundance of separate subpopulations throughout its range, are unknown. Historically, the species appeared to fluctuate in abundance as noted during forest insect and disease surveys led by the Canadian Forest Service from the 1940s to the 1980s. During these historical surveys, although larval and adult abundance was enumerated, it was recorded using vague descriptions of defoliation levels on trees or groups of trees (for example, 50%, 100%). The information in these historical forestry reports provides evidence of extreme fluctuations.

Threats and limiting factors

Impacts from the spread of non-native Spongy Moth (Lymantria dispar dispar) and other larval pest species are the most serious and plausible threat to Finlayson’s Oakworm Moth. Spongy Moth defoliates oak trees, decreasing this food supply and making the leaves less palatable to oakworm moth larvae. Applications of Btk are routinely made to control Spongy Moth. This pesticide is sprayed on foliage and, when ingested, directly kills Finlayson’s Oakworm Moth larvae within a few days. The decision to control Spongy Moth is made by the county, town or individual landowner, and many individuals fail to consider the threat to native lepidopteran species at risk in their Spongy Moth spray programs. Additional threats include ecosystem modifications that result from vegetation succession and fire suppression, and the cumulative threats to oak host trees (for example, diseases). Housing, urban, and agricultural development continues to fragment much of the open meadow habitats, as does mining, quarrying and road construction. Light pollution is also thought to impact moth subpopulations at a local scale.

Protection, status and ranks

Finlayson’s Oakworm Moth is not legally protected in Canada. The species’ conservation status is imperilled both globally and provincially (G2 and S2 respectively).

Technical summary

Anisota finlaysoni

Finlayson’s Oakworm Moth

Anisote de Finlayson

Range of occurrence in Canada: Ontario

Demographic information

Generation time

1 year, based on the biology of the moth.

Is there an [observed, inferred, or projected] continuing decline in number of mature individuals?

Unknown. Insufficient data.

Estimated percent of continuing decline in total number of mature individuals within [5 years or 2 generations, whichever is longer up to a maximum of 100 years]

Unknown. Insufficient data.

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last [10 years, or 3 generations, whichever is longer up to a maximum of 100 years]

Unknown. Insufficient data.

[Projected or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations, whichever is longer up to a maximum of 100 years].

Unknown. Insufficient data.

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over any period [10 years, or 3 generations, whichever is longer up to a maximum of 100 years], including both the past and the future.

Unknown. Insufficient data.

Are the causes of the decline a) clearly reversible, b) understood, and c) ceased?

1. No. Historical habitat loss and fragmentation are not reversible
2. No. The moth historically occurred at outbreak levels. However, species-specific and locality information is vague Habitat loss is inferred but there are additional unknown contributors to declines
3. No. There are numerous cumulative ongoing threats in known and potential habitats

Are there extreme fluctuations in number of mature individuals?

Unknown. Insufficient data.

Extent and occupancy information

Estimated extent of occurrence (EOO)

41,592 km²; calculated based on convex polygon around historical and extant subpopulations. The moth can occur at low abundance and may reside within historical sites with suitable habitat.

Index of area of occupancy (IAO) (2x2 grid value).

> 336 km² (84 grid cells; includes historical and extant sites)

Is the population “severely fragmented” that is, is >50% of its total area of occupancy in habitat patches that are (a) smaller than would be required to support a viable population, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

A. No. It is not known if habitat patches support viable subpopulations, but it is known that the moth can occur at low abundance within oak patches.

b. Yes. Historically, oak savannah habitats were more connected and widespread, but present-day ecosystems are isolated and fragmented. Fragmented habitat, poor dispersal ability and a low number of separate and isolated extant subpopulations across unsuitable habitat support this.

Number of “locations”

7-30. There are 15 extant subpopulations of Finlayson’s Oakworm Moth that span a minimum of 7 counties in southern Ontario. Each county can be further subdivided into municipalities, and these municipalities may have differing spray regimes. Given the low detection probability of the species, there are likely undocumented subpopulations of the moth, and these subpopulations would also be threatened from pesticide spraying done to control Spongy Moth. The plausible range of locations is estimated at 7 (counties with extant subpopulations) to 30 (minimum number of municipalities with potential extant subpopulations).

Is there an [observed, inferred, or projected] decline in extent of occurrence?

Yes. Inferred decline based on current and ongoing threats to habitat quality and quantity (see Threats and Habitat trends).

Is there an [observed, inferred, or projected] decline in index of area of occupancy?

Yes. Inferred decline based on current and ongoing threats to habitat quality and quantity (see Threats and Habitat trends).

Is there an [observed, inferred, or projected] decline in number of subpopulations?

Yes. Inferred decline based on current and ongoing threats to habitat quality and quantity (see Threats and Habitat trends).

Is there an [observed, inferred, or projected] decline in number of “locations”?

Yes. Inferred decline based on the threat of potential spray of pesticide to control non-native Spongy Moth.

Is there an [observed, inferred, or projected] decline in [area, extent and/or quality] of habitat?

Yes. Inferred decline based on current and ongoing threats to habitat quality and quantity (see Threats and Habitat trends).

Are there extreme fluctuations in number of subpopulations?

No. Historical data document moth larvae at outbreak abundance. However, species-specific and locality information is vague, and the moth may persist undetected.

Are there extreme fluctuations in number of “locations”?

No

Are there extreme fluctuations in extent of occurrence?

No

Are there extreme fluctuations in index of area of occupancy?

No

Number of mature individuals (in each subpopulation)

Subpopulations (give plausible ranges)

81 known subpopulations (>15 extant; 65 historical)

Most records are presence/not detected and/or the abundance was not recorded. It is not possible to determine subpopulation size. See Appendix 3.

Total

Most records are presence/not detected and/or the abundance was not recorded. It is not possible to determine population size. See Appendix 3.

Quantitative analysis

Is the probability of extinction in the wild at least [20% within 20 years or 5 generations whichever is longer up to a maximum of 100 years, or 10% within 100 years]?

Unknown. Analysis not conducted.

Threats (direct, from highest impact to least, as per IUCN Threats Calculator)

Was a threats calculator completed for this species? Yes, see Appendix 2. Overall assigned threat impact High.

Key threats were identified as:

• 9.3 Agricultural and forestry effluents (High-Low impact)
• 7.3 Other ecosystem modifications (Medium impact)
• 8.1 Invasive non-native/alien species/diseases (Medium impact)
• 1.1 Housing and urban areas (Low impact)
• 2.1 Annual and perennial non-timber crops (Low impact)
• 3.2 Mining and quarrying (Low impact)
• 4.1 Roads and railroads (Low impact)
• 9.6 Light pollution (Low impact)

What additional limiting factors are relevant?

• Larvae are dependent on specific oak (Quercus spp.) species to complete their life cycle
• Adults do not feed, so larvae must consume all necessary energy to sustain individuals through pupation to the adult stage (mating, egg development and oviposition)
• Small subpopulation size, both spatial area (for example, limited habitat) and low moth abundance
• Poor dispersal ability of females and short life span may limit (re)colonization of habitats
• Increasing dense vegetation may limit the female’s pheromone plume and ability for males to detect calling females

Rescue effect (immigration from outside Canada)

Status of outside population(s) most likely to provide immigrants to Canada.

Not applicable. The species has only been recorded from Canada and seems to be a Canadian endemic.

Is immigration known or possible?

Not applicable. The species has only been recorded from Canada and seems to be a Canadian endemic.

Would immigrants be adapted to survive in Canada?

Not applicable. The species has only been recorded from Canada and seems to be a Canadian endemic.

Is there sufficient habitat for immigrants in Canada?

Not applicable. The species has only been recorded from Canada and seems to be a Canadian endemic.

Are conditions deteriorating in Canada?

Yes. There is an inferred decline in the area, extent, and quality of habitat.

Are conditions for the source (that is, outside) population deteriorating?

Not applicable. The species has only been recorded from Canada and seems to be a Canadian endemic.

Is the Canadian population considered to be a sink?

Not applicable. The species has only been recorded from Canada and seems to be a Canadian endemic.

Is rescue from outside populations likely?

Not applicable. The species has only been recorded from Canada and seems to be a Canadian endemic.

Data sensitive species

Is this a data sensitive species?

No

Status history

COSEWIC status history: Designated Special Concern in December 2023.

Status and reasons for designation:

Status:

Special Concern

Alpha-numeric codes:

not applicable

Reasons for designation:

This moth is known only from Canada and is restricted to oak habitats in southern Ontario including savannah, woodland, forest edge, and other semi-open areas. It is exposed to many threats including competition from the invasive Spongy Moth during the larval stages and the impact of Btk pesticide used to control this non-native moth. Other threats include ecosystem modification from fire suppression and the decline of oak trees.

Applicability of criteria

Criterion A (Decline in total number of mature individuals): Not applicable. Insufficient data to reliably infer, project or suspect population trends.

Criterion B (Small distribution range and decline or fluctuation): Not applicable. Comes close to meeting Endangered, B2ab(i,ii,iii,iv)c(iv). The IAO < 500 km² meets threshold for Endangered. There is an inferred and projected continuing decline in extent of occurrence; index of area of occupancy; area, extent, and quality of habitat; and number of subpopulations, taking into account the cumulative threats from Spongy Moth defoliation and control, ecosystem modifications and oak diseases. The moth may experience extreme fluctuations; however, the data are not sufficient to estimate fluctuations in adult population size. The population is not severely fragmented and likely occurs at >10 locations.

Criterion C (Small and declining number of mature individuals): Not applicable. Number of mature individuals unknown.

Criterion D (Very small or restricted population): Not applicable. Number of mature individuals and vulnerability to rapid and substantial population decline are unknown.

Criterion E (Quantitative analysis): Not applicable. Analysis not conducted.

Meets the following Special Concern categories:

• b. the wildlife species may become Threatened if factors suspected of negatively influencing the persistence of the wildlife species are neither reversed nor managed with demonstrable effectiveness) and
• c. the wildlife species is near to qualifying, under any criterion, for Threatened status

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2019)

Wildlife species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special concern (SC)
(Note: Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.)

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at risk (NAR)
(Note: Formerly described as “Not In Any Category”, or “No Designation Required.”)

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data deficient (DD)
(Note: Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” [insufficient scientific information on which to base a designation] prior to 1994. Definition of the [DD] category revised in 2006.)

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.

Wildlife species description and significance

Name and classification

English common name: Finlayson’s Oakworm Moth; Hornless Oakworm Moth

French common name: Anisote de Finlayson

Phylum: Arthropoda - arthropods

Class: Insecta - insects

Subclass: Pterygota - winged insects

Order: Lepidoptera - butterflies and moths

Suborder: Glossata

Infraorder: Heteroneura

Superfamily: Bombycoidea - silk moths, sphinx moths, and allies

Family: Saturniidae - giant silk moths

Subfamily: Ceratocampinae - royal moths

Genus: Anisota Hübner 1820

Species: A. finlaysoni Riotte 1969

Type locality: Shannonville, Ontario (ON)

Taxonomic background and similarities:

Finlayson’s Oakworm Moth (Anisota finlaysoni) is part of the genus Anisota, which is exclusive to North and Central America. There are 14 known species with a geographic range from Honduras to southern Canada (Ferguson 1971; Riotte and Peigler 1980; Tuskes et al. 1996). Five species occur in Canada: Finlayson’s Oakworm Moth (A. finlaysoni), Manitoba Oakworm Moth (A. manitobensis), Orange-striped Oakworm Moth (A. senatoria), Spiny Oakworm Moth (A. stigma), and Pink-striped Oakworm Moth (A. virginiensis). Spiny Oakworm Moth, Pink-striped Oakworm Moth, and Orange-striped Oakworm Moth have overlapping ranges with Finlayson’s Oakworm Moth.

Finlayson’s Oakworm Moth belongs to a complex of three species, known as the senatoria species complex, whereby the morphological similarities between these three species are difficult to distinguish. The senatoria complex includes Orange-striped Oakworm Moth and Peigler's Oakworm Moth (A. peigleri). Peigler’s Oakworm Moth does not occur in Canada and ranges across the southeastern United States (Tuskes et al. 1996).

Finlayson’s Oakworm Moth was originally found in 1946 when a farmer in Shannonville, ON alerted the Department of Agriculture that unknown caterpillars were defoliating his oak trees (Riotte and Peigler 1980). At the time, only Orange-striped Oakworm Moth had been described and so caterpillars with similar morphological characters were recorded as such. However, through the work of Dr. L.R. Finlayson (Research Officer, Canada Department of Agriculture, Belleville, ON), Finlayson’s Oakworm Moth was determined to be morphologically unique from the closely-related Orange-striped Oakworm Moth (Ferguson 1971; Riotte and Peigler 1980). Finlayson recognized the insect as a new species and continued to collect and study the insect until his death in 1965. Finlayson’s collection was accessioned to the Department of Entomology and Invertebrate Zoology at the Royal Ontario Museum, where J.C.E. Riotte described Finlayson’s Oakworm Moth and named it in recognition of Finlayson (Riotte and Peigler 1980).

Tuskes et al. (1996) suggest that there are no reliable diagnostic features in the genitalia to differentiate Finlayson’s Oakworm Moth from Orange-striped Oakworm Moth and that Finlayson’s Oakworm Moth is not a full species as described by Riotte (in Ferguson 1971). However, current moth taxonomic information sources treat Finlayson’s Oakworm Moth as a full valid species (for example, Pohl et al. 2016; Schmidt pers. comm. 2023) and this taxonomy is being followed.

Morphological description

Finlayson’s Oakworm Moth undergoes complete metamorphosis with four distinct developmental life stages: egg, larva (five instars), pupa, and adult. The species shares some morphological characteristics with the Orange-striped Oakworm Moth, and for many years the two were treated as one species. The information below, which includes comparisons with Orange-striped Oakworm Moth, is summarized from Ferguson (1971), Riotte and Peigler (1980), Tuskes et al. (1996) and Kohalmi pers. obs. (2023).

Eggs

Finlayson’s Oakworm Moth eggs are oviposited (laid) in clusters. Up to several hundred eggs are placed at the ends and undersides of host plant leaves situated peripherally on the tree (Kohalmi pers. obs. 2023). Eggs are bright yellow when first laid, turn a dark reddish brown after a few days and then turn grey immediately prior to hatching.

Larvae

First instar larvae are approximately 5 mm long and have a hairless, light yellowish body with faintly pigmented lines. One of these pigmented lines is along the dorsum, one line along the spiracles (openings along the side of the body, which allow air to enter the trachea), and two broader lines between the dorsum and spiracles. Setae (stiff hairs) are thin and small, and the two scoli (thorny projections from the body) on the 2nd segment of the thorax are only slightly thicker.

The 2nd to 5th instars have a blackish-brown body with yellow lateral stripes and a blackish red-brown head. There are several yellow longitudinal stripes consisting of two narrow dorsal ones reaching the 7th abdominal segment, a straight subdorsal one, an undulate supraspiracular which breaks between segments, and a straight and interrupted infraspiracular line. There is a light-yellow ventral median stripe. Spiracles are black. The bases of the infraspiracular spines are yellow. The pronotum (dorsal saddle-shaped patch behind head) is black with yellowish borders coinciding with the second lateral yellow stripe and is heavily chitinized. The approximate instar lengths are 2nd instar 10mm; 3rd instar 21 mm; 4th instar 32 mm; and 5th instar 50 mm.

The stripes of late 5th instar Finlayson’s Oakworm Moth larvae are bright yellow, whereas those of Orange-striped Oakworm Moth larvae are typically burnt orange. The hairs (termed scoli) on the second segment on the thorax of 5th instar Finlayson’s Oakworm Moth are < 1 mm long whereas those of Orange-striped Oakworm Moth are approximately 5 mm long (Kohalmi pers. obs. 2023). This morphological trait distinguishes these two species. Late-stage larvae are readily identifiable in the field.

Pupae

The pupae are slender, spiny, and blackish-brown. The cremaster (tip) is branched (termed bifurcated) (Ferguson 1971; Riotte and Peigler 1980) (Figure 1). Pupation of Finlayson’s Oakworm Moth is unstudied.

Adults

Adults are sexually dimorphic (Figure 1). Female forewings are 24-30 mm long and male forewings are 17-20 mm long (Ferguson 1971; Riotte and Peigler 1980).

Female wings are thinly scaled and are tawny ochreous when compared to Orange-striped Oakworm Moth. The underside of female wings has an ochreous-yellow suffusion whereas the underside of male wings has a distinct yellow/brassy coloration (Ferguson 1971; Riotte and Peigler 1980). Females in some subpopulations can have a purple suffusion on the terminal area of the wings (Riotte and Peigler 1980) (Figure 1).

There is a sprinkling of dark brown scales in the apical areas of the forewings (Riotte and Peigler 1980); however, this feature is light or nearly absent in comparison to that of Orange-striped Oakworm Moth (Kohalmi pers. obs. 2023).

The yellow/brassy coloration on the underside of the wings of Finlayson’s Oakworm Moth differs from that of Orange-striped Oakworm Moth, which has a more reddish/pinkish coloration (Ferguson 1971). Normally the head, thorax, abdomen, legs, fore- and hindwings of Finlayson’s Oakworm Moth are sepia brown (Riotte and Peigler 1980). Conversely, Orange-striped Oakworm Moth has a brownish earth tone (Tuskes et al. 1996) with a red tinge (Ferguson 1971). Diagnostic characters of the species genitalia are unreliable for differentiating Finlayson’s Oakworm Moth from Orange-striped Oakworm Moth (Tuskes et al. 1996), and adult moths of these two species are difficult to differentiate in the field.

Figure 1. Finlayson’s Oakworm Moth (Anisota finlaysoni) adult female (top), pupal case from female (middle), and male (bottom), and associated label data to the right. Photos courtesy of Brad Hubley, Royal Ontario Museum, Toronto, Ontario.

Population spatial structure and variability

The population structure and variability of Finlayson’s Oakworm Moth has not been studied.

Designatable units

Finlayson’s Oakworm Moth has one designatable unit in Canada. No subspecies are recognized and there is no behavioural, or genetic information that supports a taxonomic separation below the species level. The species occurs entirely within the Great Lakes Plains National Ecological Area (COSEWIC 2021).

Special significance

Finlayson’s Oakworm Moth may be globally endemic to Canada (see Distribution).

The ecological roles of oakworm moths, in general, are poorly known. Many species in this genus occasionally increase in abundance to the point of causing severe defoliation of their oak host plants. Each life stage of Finlayson’s Oakworm Moth, and the adult parasitoids that emerge from them are a potential source of food for birds and other predators. Mature larvae wander on the ground to find suitable pupation sites and are potential food for small mammals and other predacious invertebrates. Finlayson’s Oakworm Moth pupate in the ground and are a potential source of food for subterranean wildlife (see Interspecific interactions).

Aboriginal Traditional Knowledge (ATK) is relationship-based. It involves information on ecological relationships between humans and their environment, including characteristics of species, habitats, and locations. Laws and protocols for human relationships with the environment are passed on through teachings and stories, and Indigenous languages, and can be based on long-term observations. Place names provide information about harvesting areas, ecological processes, spiritual significance, or the products of harvest. ATK can identify life history characteristics of a species or distinct differences between similar species. There is no species-specific ATK for Finlayson’s Oakworm Moth in the report.

Distribution

Global and canadian range

The global and Canadian range of Finlayson’s Oakworm Moth is restricted to a small region of southern ON (Figure 2). The northernmost records are from Lindsay, and the range extends westward along the north shore of Lake Ontario at Breslau, south to Long Point and eastward through the Niagara Peninsula to Fort Erie and Rockport.

Figure 2. Extent of Occurrence (EOO) and Index of Area of Occupancy (IAO) for Finlayson’s Oakworm Moth (Anisota finlaysoni) in Canada. Map completed by Rosie Nobre-Soares and Amit Saini (COSEWIC Secretariat).

No records for Finlayson’s Oakworm Moth are known from the United States (Tuskes et al. 1996; iNaturalist 2023). The species may range from northern New York State to south of Lake Ontario, but no individuals have been detected despite extensive searching (St. Laurent pers. comm. 2020; iNaturalist 2023). Earlier studies based on adult genitalia suggested the species occurred in Wisconsin (Lake Delton and Chippewa County) and Minnesota (Green Lake and Minneapolis) (Ferguson 1971; Hessell 1976; Riotte and Peigler 1980). However, Tuskes et al. (1996) disputed these records, suggesting that the diagnostic characters of the species’ genitalia are unreliable for differentiating Finlayson’s Oakworm Moth from Orange-striped Oakworm Moth, and that all records outside of ON are Orange-striped Oakworm Moth.

Finlayson’s Oakworm Moth is recorded from at least 81 subpopulations^{Footnote 1} (Appendix 1). Many of the subpopulations are historical^{Footnote 2} and refer to general geographic areas and are named based on nearby townships and districts. A subpopulation could have numerous sites^{Footnote 3} within a defined separation distance^{Footnote 4}. It is not possible to pinpoint the exact geospatial coordinates for many of the collection sites and subpopulations older than 20 years (that is, prior to 2003; see Appendix 1).

The larval host plants for Finlayson’s Oakworm Moth (see Habitat) have geographic ranges that are larger than the geographic range of the moth (Figure 3-7).

Figure 3. Current iNaturalist (2020) records of White Oak (Quercus alba) within the range of Finlayson’s Oakworm Moth (Anisota finlaysoni) (accessed 7 September 2020). Red dots represent single tree observations. Map completed by Rosana Nobre-Soares and Amit Saini (COSEWIC Secretariat).

Figure 4. Current iNaturalist (2020) records of Bur Oak (Quercus macrocarpa) within the range of Finlayson’s Oakworm Moth (Anisota finlaysoni) (accessed 7 September 2020). Red dots represent single tree observations. Map completed by Rosana Nobre-Soares and Amit Saini (COSEWIC Secretariat).

Figure 5. Current iNaturalist (2020) records of Northern Red Oak (Quercus rubra) within the range of Finlayson’s Oakworm Moth (Anisota finlaysoni) (accessed 7 September 2020). Red dots represent single tree observations. Map completed by Rosana Nobre-Soares and Amit Saini (COSEWIC Secretariat).

Figure 6. Current iNaturalist (2020) records of Black Oak (Quercus velutina) within the range of Finlayson’s Oakworm Moth (Anisota finlaysoni) (accessed 7 September 2020). Red dots represent single tree observations. Map completed by Rosana Nobre-Soares and Amit Saini (COSEWIC Secretariat).

Figure 7. Current iNaturalist (2020) records of Chinkapin Oak (Quercus muehlenbergii) within the range of Finlayson’s Oakworm Moth (Anisota finlaysoni) (accessed 7 September 2020). Red dots represent single tree observations. Map completed by Rosana Nobre-Soares and Amit Saini (COSEWIC Secretariat).

Extent of occurrence and area of occupancy

The extent of occurrence (EOO) of Finlayson’s Oakworm Moth in Canada, based on a convex polygon of all historical⁷ and extant^{Footnote 5} subpopulations, is 41,512 km² (Figure 2). The EOO based on extant subpopulations only is 19,310 km². Finlayson’s Oakworm Moth appears to persist at low abundance within suitable habitat patches. It is possible that the species remains within unchecked habitat patches, and that some of the subpopulations categorized as historical could be extant.

The index of area of occupancy (IAO) (2 km x 2 km grid) is 336 km² (84 grid squares) for all known subpopulations (historical and extant). The IAO based on extant subpopulations only is 140 km² (35 grid squares) (Figure 2).

Search effort

Finlayson’s Oakworm Moth records date from 1878 to 2023 (Appendix 1) and include approximately 81 subpopulations. The species can be detected during both the larval (by evidence of defoliation from larval feeding and direct observation) and adult life stages. The specific collection sites for numerous historical localities are vague and unknown, and further search effort is needed within these localities.

Larval surveys

The most effective survey method for Finlayson’s Oakworm Moth (and species in the genus Anisota) involves searching for larvae and/or evidence of larval feeding on the undersides of host plant leaves (for example, frass, veins) (Riotte and Peigler 1980; Kohalmi pers. obs. 2023). Younger larvae form clusters which can be visually located from distances up to 10 metres. Older larvae disperse and feed singly, and can consume entire leaves, except for the mid veins. Defoliation caused by Finlayson’s Oakworm Moth is most obvious from mid to late September. However, when subpopulations are small, larvae are difficult to sight, making outbreak years the most reliable years for larval detection.

The Forest Insect and Disease Survey (FIDS) began in the 1940s with the purpose of monitoring forest insects that have detrimental impacts on forest tree health (McGugan 1958). For the past 80 years, FIDS has been led by the Canadian Forest Service (van Sickle et al. 2001; Natural Resources Canada 2021). From the late 1940s until the mid-1990s, general Lepidoptera (and other insect) surveys throughout southern ON collected and reared live larvae to adults for identification (see Appendix 1) (van Sickle et al. 2001). Numerous historical Finlayson’s Oakworm Moth records came from FIDS (Appendix 3), although up until 1970, the species was recorded as Orange-striped Oakworm Moth. From 1946 to 1965, there was extensive targeted research on this moth, and it was recognized as a distinct species as early as 1946 (Ferguson 1971). These data provide most of the historical collection sites available for the moth (see Appendix 1). However, the data were not consistently collected, abundance data are not reliable, and specific locality data other than the general region or township were not recorded. Since 2006, the Ontario Ministry of Natural Resources and Forestry has published an annual Forest Health Conditions in Ontario (ON FHC) report (OMNR 2007), which has some information on Finlayson’s Oakworm Moth.

The list of historical Finlayson’s Oakworm Moth subpopulations extracted from these federal FIDS and provincial ON FHC forest insect and disease surveys (see Appendix 2 and Information Sources) was used to prioritize surveys in preparation for this status report. Fieldwork in preparation for this report was conducted on August 9-24, 2021, and focused on larval surveys at many of these historical sites (see Appendix 4 for the field report). In all, 58 sites were surveyed, for a total of 99.75 hours of cumulative search effort. No Finlayson’s Oakworm Moth larvae or adults were observed, and no evidence of larval feeding was recorded.

Adult surveys

Finlayson’s Oakworm Moth adults are large, diurnal and can be detected by visual searches during wandering transects; however, when adult abundance is low the species is difficult to detect. As is the case for all moths in the family Saturnidae, the adults do not feed, and their activity is focused on mate finding and reproducing. Thus, adult female moths are not attracted to flowers or food-based baits and are often heavy with eggs and do not fly. Blacklights and mercury vapour light traps are common approaches for surveying adult moths. Males are diurnal and, although females are active during both day and night, light trapping is considered ineffective because females are relatively sedentary. Unless the trap is immediately adjacent to females, they are unlikely to be attracted to the light.

There are 41 Finlayson’s Oakworm Moth observations from 2008 to 2023 on iNaturalist (2023). Recent surveys in 2023 recorded the moth from 12 sites north of Kingston, all within the known range of the moth (Schmidt pers. comm. 2023).

Habitat

Habitat requirements

Finlayson’s Oakworm Moth inhabits open oak woodlands and savannahs within its known range of southern ON. Moth records tend to be found within younger and more open oak stands, although this is based only on surveyor observations. The larval host plants include White Oak (Quercus alba) (Figure 3), Bur Oak (Q. macrocarpa) (Figure 4), Northern Red Oak (Q. rubra) (Figure 5), Black Oak (Q. nigra) (Figure 6), and, to a lesser extent, Chinquapin Oak (Q. muehlenbergii) (Figure 7). These oak host plants have a broader range than the moth. There are additional unknown factors that limit the moth’s distribution. These habitats are part of the Mixedwood Plains Ecozone (ESTR Secretariat 2016).

Much of the habitat information for Finlayson’s Oakworm Moth is from the type locality of Shannonville (Figure 8 and 9), where L.R. Finlayson studied the moth from 1946 up until close to his death in 1965. This habitat is a dry oak savannah, dominated by Bur Oak, Shagbark Hickory (Carya ovata), and an oak that appears to be Chinquapin Oak, but may possibly be a hybrid with Bur Oak. There is dense grass beneath the canopy with occasional shrubs of Prickly Ash (Zanthoxylum americanum) and Fragrant Sumac (Rhus aromatica) (Kohalmi pers. obs. 2023). The soil is coarse and shallow and overlies limestone bedrock with frequent outcrops of the bedrock. Similar habitat occurs near Hagersville, south of Grimsby, both east and south of Shannonville and on Wolfe Island, where larvae have been observed feeding only on Bur Oak (Kohalmi pers. obs. 2023). In Norfolk County, the species is found associated with woodlands where oak is a major component of the canopy.

In 2023, Finlayson’s Oakworm Moth larvae were found near Kingston on open-grown White Oak habitat adjacent to soy and corn cropland (Schmidt pers. comm. 2023). The larvae were observed at 12 sites scattered within the general area.

Finlayson’s Oakworm Moth has been successfully reared in captivity on White, Bur, Black and Northern Red Oak in addition to ornamental English Columnar Oak (Q. robur) (Kohalmi pers. obs. 2023). Larval rearing information based on FIDS results (McGugan 1958) documents larval feeding on seven oak species. However, these observations are from the period 1944 to 1954, when Finlayson’s Oakworm Moth was considered conspecific with Orange-striped Oakworm Moth.

Figure 8. Oak savannah at Finlayson’s Oakworm Moth (Anisota finlaysoni) type locality at Shannonville, Ontario. Photo by L. Kohalmi, 7 August 2008.

Figure 9. Oak savannah at Finlayson’s Oakworm Moth (Anisota finlaysoni) type locality at Shannonville, Ontario. Photo by L. Kohalmi, 7 August 2008.

Habitat trends

Indigenous peoples of southern ON influenced the overall land cover through their cultural practices. Extensive areas of open oak forests and savannahs were still present prior to European settlement (Butt et al. 2005). Indigenous peoples used fire as a tool for clearing land for camping and travel, improving habitat for game animals, and preparing agricultural land (Bakowsky 1993). In the early 1800s, widespread European settlement resulted in significant changes to the landscape in southern ON. Natural vegetation was cleared for agriculture, and timber and cultural burning practices gradually ceased. As time passed, urban development expanded.

Native oak savannah, prairie and woodland habitats once covered more than 11,000,000 ha of North America. It is estimated that 800-2,000 km² of these vegetation community types existed in the southern ON landscape before European settlement and subsequent land conversion (Rodger 1998). The forests and savannas that formerly existed in the region occupied by the Finlayson’s Oakworm Moth have been largely transformed by agricultural development, with an estimated 20% to 80% of land converted to agriculture within the range, depending on the eco-district (Henson and Brodribb 2005).

Prior to European settlement in southern ON, a diverse mix of vegetation and site conditions existed that supported a range of fire regimes (Nowaki and Abrams 2008). As a result of fire suppression policies in the 1920s, there was a major shift in fire regimes (for example, fires did not burn as large or frequently) which had unforeseen ecological consequences (Nowaki and Abrams 2008). This included compositional and structural changes to ecosystems, whereby open country habitats (for example, savannahs, and woodlands) converted to closed-canopy forests and fire-dependent plants were gradually replaced by shade-tolerant, fire-sensitive vegetation (Nowaki and Abrams 2008). This trend continues today with ongoing fire suppression and a decline in recruitment of oak, which in the absence of fire, are out-competed by a variety of highly competitive, later-successional, gap-opportunistic, mesophytic hardwoods such as maples (Acer spp.), beeches (Fagus spp.), cherries (Prunus spp.), and birches (Betula spp.).

The historical widespread loss of oak woodland habitats in ON results in the geographical isolation of habitat patches throughout the landscape. Except for a few larger areas of habitat, most patches are less than 0.5 ha and are poorly connected within the landscape. Despite the fact that a high proportion of these areas are designated as protected lands, habitat will likely decline in both area and quality unless ongoing actions are taken to maintain ecological function (for example, invasive native/non-native vegetation removal, prescribed fire).

Data on recent losses of oak savanna habitat are unavailable, but the area of “woodlands and wetlands” in the Long Point area (Haldimand Norfolk County) decreased by about 8% between 2011 and 2016 and by about 10% to 20% in eastern ON (Frontenac and Leeds and Grenville counties) (Statistics Canada 2022). Most of the protected extant savannah is Black Oak rather than the Bur Oak savannah preferred by the Finlayson’s Oakworm Moth. The largest extant patches of Bur Oak savannah occur in the Hamilton-Niagara and Belleville-Kingston regions. Fragments existing along roadsides and fencerows at the borders of farm properties may provide suitable bridging habitat.

In southern ON, oak woodland has become rare, small, and fragmented due to fire suppression, the introduction and spread of non-native plants, and inappropriate tree planting regimes (Tallgrass Ontario 2019) (see Threats). Oak forests are fire-dependent but require infrequent and low-intensity fires (Tallgrass Ontario 2019). In contrast, most southern ON deciduous forests are comprised of fire-intolerant trees (for example, Sugar Maple, ash [Fraxinus spp.] and American Beech [Fagus grandifolia]) and have successional tallgrass oak-dominated communities that require frequent fire (Tallgrass Ontario 2019). Prescribed burns have been undertaken on Gordon Island (Van Wieren pers. comm. 2021) and restoration efforts have been undertaken (for example, Lower Trent Conservation) (Beamer pers. comm. 2020).

Woodland habitat protection in ON is governed by local municipal official plans and tree cutting by-laws, and the habitat trends at all subpopulations are historically different based on these different management objectives/regimes.

When the type locality at Shannonville was revisited in 2007, it was discovered that several gas stations and stores had been constructed at the site since 1985 (Kohalmi pers. obs. 2023). A new residential dwelling built at the site has resulted in conversion of native grassland to lawn. A small residential subdivision and large estate homes have also been constructed nearby. Many oaks were still present and may continue to sustain viable Finlayson’s Oakworm Moth colonies (Kohalmi pers. obs. 2023).

Biology

Information on the biology of Finlayson’s Oakworm Moth is summarized from Ferguson (1971), Riotte and Peigler (1980), Tuskes et al. (1996) and Kohalmi (pers. obs. 2023)

Life cycle and reproduction

Finlayson’s Oakworm Moth has an annual generation and a complete life cycle with four distinct life stages (egg, larva, pupa, adult) (see Morphological description). The species overwinters as a pupa underground, and adults emerge from mid-June to mid-July (Riotte and Peigler 1980). Adults have non-functional mouthparts, do not feed, and rely on fat reserves accumulated during the larval life stage. The average lifespan of captive-bred adults is approximately 7 days (Kohalmi pers. obs. 2023). Moth records (Appendix 1) represent both reared and wild-caught specimens.

The daily activity patterns of adult Finlayson’s Oakworm Moth are centred around mate finding and reproduction. Mid-morning, females release sex pheromones to attract males and mating occurs from late morning (10:00-12:00) until dusk, but sometimes the females will terminate mating and begin laying eggs during the late afternoon (Tuskes et al. 1996). After mating, females lay clusters of eggs on the underside of oak leaves (Tuskes et al. 1996; Kohalmi pers. obs. 2023).

Oviposition is rarely observed; however, one account on June 28, 1967 noted oviposition at 15:00, and ~400 eggs were counted from three egg clusters on three White Oak trees (Ferguson 1971; Riotte and Peigler 1980). The period from oviposition to egg-hatch lasts approximately 12 to 15 days (Riotte and Peigler 1980; Kohalmi pers. obs. 2023). After hatching, the larvae remain clustered, apparently working as a unit to consume host plant leaves. Larvae complete their feeding by the 5th instar, sometime in late August to early September. The larvae drop to the soil, search for a suitable burrow site and burrow 25-100 mm into the soil adjacent to host trees. The larva builds an earthen cell in which it overwinters as a pupa, emerging as an adult the following spring (Johnson and Lyon 1976).

Physiology and adaptability

Little is known about the physiology and adaptability of Finlayson’s Oakworm Moth. Larvae are known to feed on at least four different oak species (see Habitat). The geographic ranges of these host species extend beyond the known range of the moth, suggesting that additional unknown factors must limit the moth’s distribution.

Dispersal and migration

Like all silk moths, Finlayson’s Oakworm Moth adults live less than a week. The dispersal capability of adult moths is not known, although egg-laden females do not disperse far given their heavy weight (Tuskes et al. 1996). Based on information about the Manitoba Oakworm Moth, males fly well (Henne pers. comm. 2021) but females are poor fliers (Riotte and Peigler 1981; Tuskes et al. 1996). Finlayson’s Oakworm Moths do not migrate.

It is unknown whether Finlayson’s Oakworm Moth habitat meets the definition of severe fragmentation^{Footnote 6}. Historically, oak savannah habitats were more connected and widespread, but present-day ecosystems are isolated and fragmented with large areas of intervening unsuitable habitat. Given the moth’s biologically limiting factors (for example, poor dispersal ability, non-feeding adults) and the cumulative threats across the landscape (see Threats), the extant subpopulations may not be viable even in small habitat patches and at low abundances. However, there are no data to support whether the moth is present in these habitat patches, and the viability of these habitat patches is unknown.

Interspecific interactions

Finlayson’s Oakworm Moth is sympatric with the Pink-striped Oakworm Moth (Anisota virginiensis). However, there is no information on competitive interactions between the two species, and reproductive isolation (such as pheromone differentiation and different temporal flight periods) prevents hybridization.

Hybridization

At one point, it was thought that Finlayson’s Oakworm Moth might hybridize with Orange-striped Oakworm Moth in the western part of its range (that is, Norfolk County). Recent data from pheromone trails and genetic barcoding do not show evidence of hybridization between these two species (Schmidt pers. comm. 2023).

Host plant

Larvae are known to feed on at least four species of oaks within their range in ON (see Habitat).

Parasitism

Finlayson’s Oakworm Moth larvae are subject to parasitism by wasps and flies. Early stage (particularly first and second instar) Finlayson’s Oakworm Moth larvae flick the anterior part of their body back and forth in concert when disturbed, possibly to deter parasitoid wasps from injecting their eggs into the larvae. There are native oakworm moth parasitoids, some of which have been reared from Finlayson’s Oakworm Moth larvae. These native parasitoids usually play an important role in terminating outbreaks of oakworms, but their role during host oakworm endemic phases is unknown.

The braconid wasp, Hyposoter fugitivus (Appendix 4), has been observed on Finlayson’s Oakworm Moth (Kohalmi pers. obs. 2023). This wasp attacks young larvae < 10 mm in length (Peigler 1994). The female wasp oviposits its eggs inside the young host larvae. The developing wasp larvae pupate inside the Finlayson’s Oakworm Moth host larva, resulting in death of the host by the 4th instar. The other wasp species observed belongs to the wasp family Ichneumonidae and has been observed to parasitize Finlayson’s Oakworm Moth. It is larger than H. fugitivus and appears to be much less common. It has thus far not been identified, but resembles Habronyx magniceps (Hymenoptera: Ichneumonidae), which parasitizes the related Orange-striped Oakworm Moth (Henne 2004).

Two species of unidentified parasitic flies belonging to the family Tachinidae have also been observed in association with Finlayson’s Oakworm Moth larvae. The first, a single maggot of a large fly has been observed to exit from an overwintered pupa on two occasions (Kohalmi pers. obs. 2023). The second species, a smaller tachinid fly that is much more common, exits and kills overwintered pupae (Kohalmi pers. obs. 2023). One to three fly larvae feed and develop in each parasitized host. This second tachinid also parasitizes Orange-striped Oakworm Moth.

Defence mechanisms

The putative aposematic (warning) coloration of larval stages (black body with bright yellow longitudinal stripes) likely deters predators. Predators may avoid consuming larvae because they sequester tannins from oak leaves . The spiny armature of the larvae and pupae may also deter predation. Adult females, like those of the Pink-striped Oakworm Moth and Orange-striped Oakworm Moth, fold back their wings, curl their abdomens forward, stiffen and drop to the ground when disturbed. The adult moth is then camouflaged with the surrounding ground vegetation. The males have reduced scaling in the centre of the forewing and, given their rapid wing beat, they resemble bees when in flight. This is an adaptation like that found in clearwing moths in the genus Hemaris.

Predation

In June 1967 hundreds of adult Finlayson’s Oakworm Moths were observed at Shannonville resting on blades of grass beneath oak trees (Kohalmi pers. obs. 2023), where they would be vulnerable to near-ground predation. A male jumping spider (Phidippus clarus) was observed killing a resting adult male Finlayson’s Oakworm Moth in Prince Edward County (Kohalmi pers. obs. 2023). Bird and rodent predation are possible. Larvae on the ground searching for pupation sites and diapausing pupae beneath the soil surface would be targets for moles and voles.

Pathogens and viruses

Entomopathogens that attack insects, such as Beauveria (a fungal pathogen) and nuclear polyhedrosis virus (NPV), can cause mortality of lepidopteran larvae, especially during periods of high abundance. A white fungus tentatively identified as Beauveria bassiana has been observed to kill Finlayson’s Oakworm Moth pupae during diapause (Kohalmi pers. obs. 2023). A pathogen that may be NPV manifests during the pupal stage of Finlayson’s Oakworm Moth and turns the insides of the pupa to a black liquid (Kohalmi pers. obs. 2023). Some adults also appear to be affected by NPV, taking into account observations of moths’ insides turning dark and resulting in premature death (Kohalmi pers. obs. 2023).

Population sizes and trends

Sampling effort and methods

The sampling effort and methods used to collect information on Finlayson’s Oakworm Moth in Canada are not sufficient to assess its range-wide population size and trends. Historical (as of 1936) and present-day trend information pertaining to Finlayson’s Oakworm Moth comes from federal and provincial annual forest insect and disease surveys (FIDS) (McGugan 1958). Numerous historical records of Finlayson’s Oakworm Moth are from FIDS (Appendix 3). It should be kept in mind, however, that up until 1970, the species was recorded as Orange-striped Oakworm Moth. Using these reports, the moth’s presence was assessed as a percentage of defoliation on oak host trees (see Appendix 3 and Information Sources). The metapopulation structure of Finlayson’s Oakworm Moth has not been studied.

Abundance

It is not possible to estimate the abundance of Finlayson’s Oakworm Moth in Canada. The moth’s presence at historical sites was noted as an outbreak in the annual FIDS reports. However, moth abundance during outbreaks was not assessed and was instead reported as a percentage of tree defoliation (for example, 100% defoliation, lightly defoliated) or as a general category of abundance (for example, low, high) (for example, as described in SAJAN 1981; 1982).

Fluctuations and trends

Finlayson’s Oakworm Moth observation data from 1946 to 2021 (Figure 10 and 11) show cyclic population fluctuations between 1950 and the mid-1970s, followed by asynchronous population fluctuations and, more recently, a decline in observations. These early population cycles coincide with observations from federal FIDS surveys, which were consistent up to the 1980s (Figure 10 and 11). No federal FIDS or ON FHC observations for Finlayson’s Oakworm Moth were found beyond 2006, suggesting an absence of outbreaks. A significant decline is also observed beyond 1985 when only the government-generated data (Figure 10 and Figure 11) are considered. It is also possible that moth abundance is so low now that outbreaks no longer occur.

In some years, the larvae of the closely related Orange-striped Oakworm Moth increase to such high abundance in areas of the eastern United States, that homeowners seek control measures (Coffelt and Schultz 1993). In ON, both species are of major importance, capable of killing or severely defoliating trees or shrubs (Nystrom and Ochoa 2006). Outbreaks of Orange-striped Oakworm Moth are typically localized, but severe defoliation may extend across large areas (MacAloney and Ewan 1964). Outbreaks can occur repeatedly in different localities within the same general areas, with infestation levels varying from one year to the next (Rose and Lindquist 1982).

There are numerous factors that contribute to fluctuations in moth abundance. Since there are no baseline data, it is not possible to conclude that there is a decline if the baseline starts at outbreak abundance levels (Didham et al. 2020). The inconsistent data collection for Finlayson’s Oakworm Moth observations presents additional unknowns which affect the interpretation of population fluctuations and trends. Up to 2006, most of the available Finlayson’s Oakworm Moth data are from FIDS and ON FHC reports (Figure 11). After 2006 the compiled data consist of iNaturalist (2023) and targeted independent researcher input.

Figure 10. Number of reported observations for Finlayson’s Oakworm Moth (Anisota finlaysoni) from 1946 to 2021 based on all available data. Observations from 1946 to 1986 (see Appendix 1) recorded moth presence based on a subjective measure of host tree defoliation. It is not possible to determine moth abundance from these data.

Figure 11. Forest Insect and Disease Survey (FIDS) observations of Finlayson’s Oakworm Moth (Anisota finlaysoni) by year. See Appendix 3 for data sources. In 1986 the program ceased; however, there are a few years between 1987 and 2021 when government-led surveys were conducted.

Rescue effect

There are no known extant populations of Finlayson’s Oakworm Moth outside of Canada; at present the species is considered endemic.

Threats and limiting factors

Finlayson’s Oakworm Moth appears vulnerable to the cumulative effects of various threats, including impacts from non-native invasive species, such as Spongy Moth (Lymantria dispar dispar), and efforts to control this non-native moth through pesticide applications. The nature, scope, and severity of these threats has been described in Appendix 2, following the IUCN-CMP (International Union for the Conservation of Nature–Conservation Measures Partnership) unified threats classification system (see Salafsky et al. 2008 for definitions and Master et al. 2012 for guidelines).

The threat assessment process consists of assessing impacts for each of 11 main categories of threats and their subcategories, based on the scope (proportion of population exposed to the threat over the next 10-year period), severity (predicted population decline within the scope during the next 10 years or 3 generations, whichever is longer up to ~100 years), and timing of each threat. The overall threat impact is calculated by considering the separate impacts of all threat categories.

Threats for Finlayson’s Oakworm Moth were assessed over the entire Canadian range. The overall threat impact from this assessment is High, corresponding to an anticipated decline of 10% to 70% over the next ten years. These values are to be interpreted with caution, as they may be based on subjective information, such as expert opinion, although efforts have been made to corroborate the scores with available studies and quantitative data.

Belleville-Kingston, Hamilton-Niagara, and the Norfolk Sand Plain are three regions with historical and recent observations of Finlayson’s Oakworm Moth. Some threats are common to all three regions and other threats are unique to each region. Details are discussed below under the IUCN-CMP headings and numbering scheme, from highest to lowest impact.

IUCN threat 9: pollution (high-low impact)

9.3 agricultural and forestry effluents (high-low impact)

Bacillus thuringiensis kurstaki (Btk) is a component of commercial pesticides that use spores of a naturally occurring pathogenic bacterium to control defoliating larvae, although the bacterium also affects most non-target butterfly and moth larvae. Although Btk has often been promoted as being specific to the target species, most of the lepidopteran larvae used in a comprehensive study were found to be susceptible to Btk (Kreig and Langenbruch 1981). Controlled field studies have demonstrated that this pesticide affects non-target Lepidoptera (Rastall et al. 2003).

The geographic range of non-native Spongy Moth overlaps with that of Finlayson’s Oakworm Moth. Spongy Moth was first detected in ON in 1969 and the first widespread defoliation occurred in 1981 (MNRF 2023). Since then, there have been outbreaks every 7-10 years, with the most recent one occurring in 2020-2022. Applications of Btk are routinely deployed to control outbreaks of Spongy Moth and other economically important moth larvae in many areas, including ON. The spatial area covered by Btk applications varies yearly and depends on the extent to which Spongy Moths are present. Spongy Moth larval activity, and the application of Btk to control larval outbreaks (typically in early April to May) does not overlap with Finlayson’s Oakworm Moth larval activity.

Spongy Moth larvae appear in early spring and Finlayson’s Oakworm Moth larvae appear in the summer, although the effects of Btk application have been shown to persist for at least three years (Miller 1990, 1992). Although Btk is promoted as having a short lifespan, there is evidence that the live bacterial spores can persist in the environment (Seligy et al. 1997). Viable Bacillus thuringiensis endospores were recovered from White Spruce (Picea glauca) foliage one year after treatment (Reardon and Haissig 1984). Viable spores can also persist in soil for several years and can germinate and multiply in insect larvae (Vilas-Boas et al. 2000). In addition to causing infection via ingestion, Btk can cause septicemia in invertebrates by introduction through abrasions and lesions in the cuticle (Addison 1993). This is especially relevant to Finlayson’s Oakworm Moth larvae which burrow and pupate in coarse soil which has the potential to cause abrasions in the larval cuticle.

From the mid-1980s to the present, the decline of Finlayson’s Oakworm Moth is correlated with the spread and geographic range expansion of Spongy Moth and associated Btk control measures. Btk applications carried out by the Ontario Ministry of Natural Resources throughout the 1980s culminated in a large-scale application throughout central and southern ON in 1990 (Meating et al. 1990). The Ministry of Natural Resources stopped its Btk spraying program in 1992 but spraying is still carried out in some conservation areas and municipalities (Linton 2015; COSEWIC 2019).

Neonicotinoids are a new class of systemic insecticides that are used in agriculture primarily as a seed treatment. Neonicotinoid insecticides are a potential threat where plowed soil previously planted with treated seed drifts onto nearby Finlayson’s Oakworm Moth habitat. Oak trees in fencerows and roadsides bordering fields planted with treated seed have the potential to absorb these systemic insecticides. Neonicotinoids were introduced and became widely used in the 1990s. Currently there is no information on Finlayson’s Oakworm Moth susceptibility to neonicotinoids; however, the use of this insecticide would not have been a factor in the 1980s decline of Finlayson’s Oakworm Moth.

9.5 air-borne pollutants (unknown impact)

Carbon dioxide (CO₂) pollution and carbon/nitrogen ratios impact oak plant health and therefore the insect's egg-laying success, development, and other biological processes. The impacts of CO₂ and other airborne pollution on Finlayson’s Oakworm Moth are unknown.

9.6 light pollution (low impact)

Light pollution from residential, industrial, and commercial development is a growing threat across the range of Finlayson’s Oakworm Moth. Many nocturnal insects are attracted to artificial lights, including moths in the genus Anisota. Male moths are not attracted to lights; however, females are attracted to light, and light pollution can arrest normal mating and egg-laying activities and expose the moths to predation by birds (Tuskes et al. 1996). Dozens of female Pink-striped Oakworm Moth were observed resting on the walls at a brightly lit gas station wall at night; they were thus exposed to bird predation and prevented from egg-laying (Kohalmi pers. obs. 2023). This same impact could affect Finlayson’s Oakworm Moth. However, the light source would need to be close to Finlayson’s Oakworm Moth females to have a direct impact on them, . Therefore, a low scope was chosen.

IUCN threat 7: natural system modifications: impact medium

7.3 other ecosystem modifications (medium impact)

Oak trees, in general, are sensitive to environmental stress and even small changes to the growing environment can compromise tree health. Damage to the tree such as changes in the air-to-moisture ratio in soil, soil compaction to the root zone, or damage to the tree during construction activities, can weaken or stress the tree. Numerous diseases can affect oak trees and have a cumulative effect on the quality and quantity of oak tree habitat available to Finlayson’s Oakworm Moth. Diseases include:

Oak decline

Oak trees within the range of Finlayson’s Oakworm Moth are at risk of “oak decline” (Allen and Kuta 1994). Oak decline is not caused by a single pathogen but has instead been attributed to several cumulative factors that weaken the tree (for example, flooding, soil compaction), making it more vulnerable to forest pests.

Armillaria Root Rot (Armillaria spp.) is a fungal disease first documented in Canada in 1918 and now known from forested areas across Canada. The species causes a significant disease of young conifers in the prairie provinces (Hiratsuka 1987) that leads to rot and eventually the death of the tree (Catton et al. 2007).

Two-lined Chestnut Borer (Agrilus bilineatus) is a beetle whose larvae bore into oak trees; after 3-4 years of branch dieback, tree mortality can occur (Oak 2002; Natural Resources Canada 2015).

Cynipid gall wasps (Hymenoptera: Family Cynipidae). Numerous cynipid species are known to form galls on oak trees. Gall wasps do not kill the tree; however, they make the tree more susceptible to other diseases.

Oak Twig Girdler/Pruner (Anelaphus parallelus) is a longhorn beetle. Adults emerge in late summer and feed on the twig tips, and eventually mate and lay eggs in these dead tips in order to provide the larvae with dead material. This feeding causes injury and offshoot development, forks, stem deformities and crooks. This then limits the growth of the tree and weakens its overall health.

Anthracnose is a complex of numerous fungi, which causes irregular brown or tan patches on leaf surfaces, distorted appearance, and eventual premature drop. Other symptoms include twig or branch dieback, and eventual damage from secondary infection.

Tubakia Leaf Spot (Tubakia dryina) is an example of a fungal disease that causes spots on the leaves of numerous tree and plant species, including oaks. The damage is cosmetic; however, the fungus does weaken the tree and make it more susceptible to other, secondary diseases and eventual death.

Bacterial Leaf Scorch (Xylella fastidiosa) is a bacterium that grows within and plugs the xylem of the tree, preventing nutrients from getting to the shoots and crown. Eventually, leaf scorch leads to the death of the tree.

Oak Wilt (Bretziella fagacearum) is a fungus that is spread by insects or by root grafting. Infection leads to leaf wilt, discoloration, defoliation, and eventually the death of oak trees.

Cutworms. Oak trees can also be weakened by defoliation by native species of Lepidoptera, such as cankerworms that are active in the fall (Alsophila pometaria) and spring (Paleacrita vernata). This predisposes the trees to other insect pests and diseases such as oak decline (Oak 2002). For example, significant oak mortality and oak decline occurred in the town of Oakville’s Iroquois Shoreline Woods Park in 2002 due to Armillaria Root Rot (Armillaria gallica) and Two-lined Chestnut Borer (Agrilus bilineatus) (Williams et al. 2013).

Spongy Moth subpopulations can attain outbreak levels and cause widespread defoliation of many hardwood tree species, especially oaks. During field surveys conducted to inform this status report, extensive Spongy Moth defoliation was observed in surveyed habitats in 2021 (see Appendix 4). The larval activity period of Spongy Moth occurs before that of Finlayson’s Oakworm Moth, and Spongy Moth larvae can consume large amounts of oak foliage, leading to a decline in the quality and quantity of available food and a reduction in future egg-laying sites (see 9.3).

Fire suppression leads to the growth and infilling of understory native and non-native shrubs, and these plants may suppress recruitment of oak host plant seedlings and gradually change the ecosystem. For example, invasive Common Buckthorn (Rhamnus cathartica), which is present in Finlayson’s Oakworm Moth, habitat blocks sunlight that would otherwise reach the ground, and this blockage of light affects soil temperature for pupating Finlayson’s Oakworm Moth. The roots of this invasive plant may also interfere with the quality of larval burrowing habitat. Female Anisota moths are born with fully developed unfertilized eggs. Females are heavy and in general will remain close to their pupal emergence site. They will sit and emit a sex-attractant pheromone, which creates a plume around them. Males are more mobile and will actively patrol habitats in search of female pheromone plumes. Over the past few decades, invasive non-native plants have slowly grown into these once-open oak savannah habitats, filling space within them. The pheromone plumes the disperse as far nor reach the sphere where once it may have. The impacts of these habitat changes on the moth have not been studied.

IUCN threat 8: invasive and other problematic species and genes: impact medium

8.1 invasive non-native/alien species/diseases (medium impact)

Spongy Moth larvae adversely affect host tree health and make the tree less palatable to Finlayson’s Oakworm Moth larvae. Plants have phytochemical defences that are triggered by tissue injury caused by herbivorous insects (War et al. 2012). Host tree defences triggered by Spongy Moth defoliation would be high by the time Finlayson’s Oakworm Moth larvae hatch and begin feeding on the same host. Colonial early-instar Finlayson’s Oakworm Moth larvae keep the chewed leaf edges from drying out by feeding on alternative leaves (Kohalmi pers. obs. 2023). Dried leaf edges caused by previous Spongy Moth chewing may be a deterrent to Finlayson’s Oakworm Moth feeding.

Finlayson’s Oakworm Moth larvae feed in clusters, unlike Spongy Moth larvae which spread throughout the whole tree and can affect most leaves even when the tree is not completely defoliated. The phytochemical defences triggered by Spongy Moth and the decline in the quality of the food resources available to developing Finlayson’s Oakworm Moth larvae are considered direct threats and are scored in 8.1. Spongy Moth defoliation reduces habitat quality and is scored under 7.3.

Female Finlayson’s Oakworm Moths typically lay eggs in one mass on a single leaf; females are selective and do not appear to lay eggs if leaf quality and orientation are unsuitable to them (Kohalmi pers. obs. 2023). This behaviour is unlike that of most other saturniid females which readily lay eggs in captivity on artificial container surfaces (Kohalmi pers. obs. 2023). Impacts of Spongy Moth larval infestations change the leaf quality of the host and may be a detriment to successful oviposition by Finlayson’s Oakworm Moth females.

Spongy Moth can also carry subpopulations of parasitic flies that can affect non-target moth species. A non-native parasitic fly, Compsilura concinnata (Diptera: Tachinidae), was repeatedly introduced to North America between 1906 and 1986 as part of a biological control program for the Spongy Moth (Boettner et al. 2000). Unfortunately, this generalist parasitoid attacks more than 200 species of native butterflies, moths, and sawflies (Elkinton and Boettner 2012), including the Orange-striped Oakworm Moth, the Spiny Oakworm Moth, and the Pink-striped Oakworm Moth (Wagner 2012).

IUCN threat 1: residential and commercial development (overall threat impact: low)

Habitat destruction through urbanization and industrial development clear suitable oak habitat. Residential and commercial development is generally dependent on human population growth. Population growth totalled 4.6% in ON from 2011 to 2016, the latter date being the year of the last published census. Ontario’s population is projected to grow 35.8% (5.3 million) from 2020 to 2046. Net migration is projected to account for 90% of population growth in 2021-2022, to decrease to 83% in 2027-2028, and to level off at 89% by 2046 (Government of Ontario 2021). Although data are unavailable, the area of habitat lost to housing and urban area development has increased over the last 10 years and is likely to continue increasing with human population growth (Government of Ontario 2021).

1.1 housing and urban areas (low impact)

The threat of residential and commercial development in small communities within and adjacent to Finlayson’s Oakworm Moth habitat has been exacerbated by human migration out of major urban centres in southern ON. Housing development is expected to be less of a threat in the Norfolk Sand Plain region because of the extensive conservation lands in the area (for example, Nature Conservancy Canada and Forest Reserve tracts). Housing development in the Greenbelt (Figure 12) and the Oak Ridges Moraine in the Greater Toronto Area (GTA) is likely to expand (Figure 13) (Environmental Registry of Ontario 2023).

Figure 12. Greenbelt area boundaries within southern Ontario. Maps created using the Ontario Ministry of Natural Resources and Forestry’s web-based “Make a Map: Natural Heritage Areas application.”

Figure 13. Oak Ridges Moraine. Maps created the Ontario Ministry of Natural Resources and Forestry’s web-based “Make a Map: Natural Heritage Areas application.”.

IUCN threat 2: agriculture and aquaculture (overall threat impact: low)

2.1 annual and perennial non-timber crops (low impact)

Incremental agricultural land conversion (< 5%) is projected to occur within the range of Finlayson’s Oakworm Moth, based on information collected over the past ten years. Between 2011 and 2021, the area of crops and pasture decreased by about 10% in Haldmand-Norfolk County, north of Lake Erie, and by 10% to 30% in Frontenac and Leeds and Grenville counties, at the east end of Lake Ontario (Statistics Canada 2022). These trends are expected to continue.

IUCN Threat 3: Energy Production and Mining (overall threat impact: Low)

3.2 Mining and quarrying (low impact)

Limestone quarries have been established in most of the Bur Oak savannah habitat, including the type locality at Shannonville. In the Belleville-Kingston region, there are limestone quarries on the outskirts of Kingston, Napanee, Shannonville, Belleville, and Picton and on the eastern shore of Prince Edward County. In the western end of the GTA and in the Hamilton Niagara region, quarries are situated near Oakville, Milton, Guelph, Kitchener, Dundas, southwest of Grimsby, south of Beamsville, and near St. Catherines. To the east of the Norfolk Sand Plain, there are some quarries on the outskirts of Hagersville and Dunneville. Four quarries are also situated southwest of Woodstock (Ministry of Northern Development, Mines, Natural Resources and Forestry 2023).

Spent quarries often fill with water and cannot be reclaimed as oak savannah. Active quarries produce limestone dust that settles, and heavily dusted leaves constitute unsuitable food resource. Quarry expansion to meet future construction needs would further reduce nearby oak savannah habitat. Some of the highest quality Bur Oak savannah occurs between Hamilton and St. Catherine’s over Ordovician and Silurian limestone formations. These formations have been designated as potential stone resource extraction areas despite being within the Greenbelt in Niagara Region (Figure 12) (Niagara Region Potential Resource Areas-Stone 2015).

IUCN threat 4: transportation and service corridors (overall threat impact: low)

4.1 roads and railroads (low impact)

Highways with heavy traffic cause impact mortality and act as dispersal barriers to adult moths. Roads and railroads potentially result in roadkill of wandering larvae. Traffic is likely to increase with human population growth throughout the range of Finlayson’s Oakworm Moth. For example, the potential for the construction of Highway 413 could impact any remaining Finlayson’s Oakworm Moth habitat in the historical range in the Milton area (AECOM 2023). No other proposed roads or railroad expansion are known in other parts of the species’ geographic range.

Low-use side roads and railroads may have a beneficial effect on moth habitat. These areas provide forest edge habitat in densely vegetated areas that have converted to a closed canopy due to ingrowth associated with fire suppression.

IUCN threat 11: climate change and severe weather (unknown impact)

11.2 droughts (unknown impact)

Droughts weaken and stress oaks, causing them to be more vulnerable to insects and diseases (see 7.3). These impacts likely differ across the range of Finlayson’s Oakworm Moth.

11.3 temperature extremes (unknown impact)

Snowpack can influence the survival of overwintering pupae. Larvae burrow 8-10 cm below ground and create a small cavity where they spin a light silk case and enter pupation. If there is less snow, this lessens the insulative protection of the snowpack and exposes overwintering individuals to lower temperatures from, for example, wind exposure and lower freezing temperatures.

11.4 storms and flooding (unknown impact)

Oak trees in the St. Lawrence Islands are affected by periodic storm damage. An increase in the scope and severity of ice storms is expected to occur, with attendant branch breakage. This increases the susceptibility of oaks to other diseases. The overall range-wide impacts of storms and flooding is unknown.

Limiting factors

Limiting factors are generally not human-induced and include intrinsic characteristics that make the species less likely to respond to conservation efforts. Limiting factors may become threats if they result in population decline. The main limiting factors for Finlayson’s Oakworm Moth are speculative but are likely a combination of the following:

Small subpopulation size

The moth’s host plants are oaks, and the moth is associated with oak-dominated woodland habitats in ON, a habitat type with a restricted geographic range and patchy distribution. Ecological theory predicts that the risk of a subpopulation going extinct in a single patch, such as an area of oak habitat, is reduced with an increase in the size of surrounding subpopulations (Hanski 1982). Finlayson’s Oakworm Moth appears to occur as small or localized subpopulations, thus preventing genetic mixing between subpopulations, and leading to inbreeding depression, which increases the chance of local extirpation.

Limited dispersal ability

Oak woodland ecosystems were connected and more widespread in the past. Present-day ecosystems are isolated and fragmented. Finlayson’s Oakworm Moth is likely not able to disperse long distances across unsuitable habitat. Female moths are not highly mobile and are unlikely to disperse far, given their heavy, egg-filled bodies. Subpopulation structure and spatially isolated habitats likely limit dispersal capabilities and population intermixing.

Natural parasitic enemies

Parasites are known to attack moths at all life stages; however, no species-specific information is available for Finlayson’s Oakworm Moth. There are native parasitoids of oakworm moths, some of which have been reared from Finlayson’s Oakworm Moth larvae (see Interspecific interactions).

Host plant specificity

Finlayson’s Oakworm Moth requires specific oak host plants in order to complete its life cycle (see Habitat).

Vulnerability to weather patterns

The overall seasonal weather patterns affect the abundance and distribution of moths at all life stages. Weather factors into the degree days and subsequent emergence of the next year’s generation. The previous year’s weather (for example, average temperature, average rainfall, frost) affects host plant growth, senescence, and abundance, and directly impacts larval health and the abundance of the next generation. Humidity and extreme winter temperatures affect larval survival, as well as the ability for the female pheromone to distribute throughout the landscape. Temperature and rainfall impact the species’ growth and adult movement.

Number of locations

The term “location”^{Footnote 7} defines a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. The size of the location depends on the area covered by the threatening event and may include part of one or many subpopulations. There are 15 extant subpopulations of Finlayson’s Oakworm Moth that span a minimum of seven counties in southern ON. Each county can be further subdivided into municipalities, and each municipality may have differing spray regimes. Given the low detection probability of the species, there are likely undocumented subpopulations of the moth, and these subpopulations would also be threatened by the use of pesticide spray to control Spongy Moth. The plausible range of locations is estimated at between seven (counties with extant subpopulations) and 30 (minimum number of municipalities with potential extant subpopulations).

Protection, status and ranks

Legal protection and status

Finlayson’s Oakworm Moth is not protected by the Canada Species at Risk Act or the Ontario Endangered Species Act. Oak host plants are also not protected under these acts. Subpopulations of Finlayson’s Oakworm Moth in Thousand Islands National Park are protected under the Canada National Parks Act. Similarly, any subpopulations of Finlayson’s Oakworm Moth present in ON provincial parks and conservation reserves would be protected under the Ontario Provincial Parks and Conservation Reserves Act. Subpopulations known from protected areas are listed in Appendix 1.

Non-legal status and ranks

The conservation status ranks for the Finlayson’s Oakworm Moth (NatureServe 2023) are:

• global Status: G2 (Imperiled) (last reviewed 10/16/2023)
• national Status: N2 (Imperiled) (last reviewed 10/16/2023)
• provincial (ON) Status: S2 (Imperiled) (last reviewed 10/16/2023)

Habitat protection and ownership

The specific collection sites for numerous historical localities are vague or unknown. Subpopulations linked to known land ownership, including those known from protected areas, are listed in Appendix 1.

Acknowledgements

Thanks are extended to the curators at museums and government institutions who were able to assist to provide records, photos, and other information about Finlayson’s Oakworm Moth during the pandemic. The status report writers would like to thank Jennifer Heron (Arthropods Specialist Subcommittee Co-chair), Rosana Soares, Joanna James, Sydney Allen, Amit Saini, and Jenny Wu (COSEWIC Secretariat).

Thanks are also extended to conservation area and park staff who assisted with access and advice for the field survey: Lisa Burnside and Lesley McDonell at Hamilton Conservation Authority; David Beamer at Lower Trent Conservation Authority; Brad McNevin and Tim Trustham at Quinte Conservation Authority; Andrea Dunn, Jennifer Roberts, Brenda Van Ryswyk, and Adam Baker at Halton Region Conservation Authority; Sandra Sharma, Adam Christie, and Kim Frohlich at Niagara Peninsula Conservation Authority; Steve Knapton at Cataraqui Conservation Authority; George Elgear and Gus Saurer at Ganaraska Region Conservation Authority; and Chris Reinhart at Long Point Region Conservation Authority.

Also, thanks are due to Tom Mason, former Curator of Invertebrates and Birds at the Toronto Zoo, and to Susan Tomchyshyn for volunteering their time, as well as to Alain Aeschelmann for providing some of the field transportation.

The report writers would particularly like to thank the many reviewers of the draft report for their thoughtful comments and useful suggestions. The Arthropods Specialist Subcommittee provided a review: David McCorquodale, Robert Buchkowski, Syd Cannings, Jeremy deWaard, Allan Harris, Colin Jones, John Klymko, Jayme Lewthwaite, Jessica Linton, Dawn Marks, Julia Mlynarek, Jeff Ogden, Leah Ramsay, John Richardson, Sarah Semmler, Brian Starzomski, Sue Chiblow (ATK), Dan Benoit (ATK), and Myrle Ballard (ATK).

Authorities contacted

• Anderson, Robert. Research Scientist, Canadian Museum of Nature, Ottawa, Ontario
• Barber, Kevin. Natural Resources Canada, Great Lakes Forestry Centre. Sault Ste. Marie, Ontario
• Dowsley, Martha. Associate Professor, Department of Anthropology, Lakehead University, Thunder Bay, Ontario
• Gardiner, Laura. Ecosystem Scientist, Parks Canada, Saskatchewan
• Gartshore, Mary. Private Consultant, Norfolk County, Ontario
• Hubley, Brad. Entomology Collection Manager. Department of Natural History. Royal Ontario Museum, Toronto, Ontario
• Johnson, Marc. Associate Professor, University of Toronto, Toronto, Ontario
• Jones, Colin. Provincial Arthropod Zoologist. Ontario Natural Heritage Information Centre, Ontario Ministry of Natural Resources and Forestry, Peterborough, Ontario
• Lambert, Sheldon. Manager, Resource Conservation, Thousand Islands National Park, Parks Canada, Mallorytown, Ontario
• Pickett, Karolyne. Wildlife Biologist, Canadian Wildlife Service, Conservation Planning and Stewardship Section, Ottawa, Ontario
• Pohl, Greg. Forest Biodiversity Researcher and Collections Manager, Natural Resources Canada, Canadian Forest Service, Edmonton, Alberta
• Porter, Trevor. Assistant Professor, University of Toronto, Toronto, Ontario
• Pruss, Shelley. Adjunct Professor, Department of Renewable Resources, University of Alberta, Species Conservation Specialist, Natural Resources Conservation Branch, Parks Canada, Fort Saskatchewan, Alberta
• Schmidt, Christian. Research Scientist, Agriculture and Agri-Food Canada. Ottawa Research and Development Centre, Ottawa, Ontario
• St. Laurent, Ryan. Ph.D. student, University of Florida, Gainesville, Florida
• Stone, Derek. Conservation and Program Manager, The Riverwood Conservancy, Ontario
• Troubridge, Jim. Retired, Agriculture and Agri-Food Canada, Ottawa Research and Development Centre, Ottawa, Ontario
• Zitani, Nina. Curator, Zoological Collections. Western University, Department of Biology, Biological and Geological Sciences Building, London, Ontario

Information sources

Addison, J.A. 1993. Persistence and nontarget effects of Bacillus thuringiensis in soil: a review. Canadian Journal of Forest Research 23(11):2329-2342.

AECOM. 2023. Highway 413. https://www.highway413.ca [accessed February 13, 2023].

Allen, M., and G. Kuta. 1994. Oak Decline. Natural Resources of Canada, Canadian Forest Service, Northwest Region, Forestry Leaflet 28, Edmonton, Alberta.

Andress, B. 2004. Short-Horned Oakworm (Anisota finlaysoni) infestation at Gordon Island: A review of the insect’s ecology, the infestation, and control options. Resource Conservation, St. Lawrence Islands National Park.

Bakowsky, W., and J.L. Riley 1992. A survey of the prairies and savannahs of southern Ontario. Pp. 7-16, in R. Wickett, P. Dolan Lewis, A. Woodliffe and P. Pratt (eds.). Proceedings of the Thirteenth North American Prairie Conference: Spirit of the Land, Our Prairie Legacy. August 6-9, 1992. Windsor, Ontario: Corporation of the City of Windsor.

Beamer, D. 2020. Personal communication to L. Kohalmi. Manager, Conservation Lands. Lower Trent Conservation.

Boettner, G.H., J.S. Elkinton, and C. Boettner. 2000. Effects of a biological control introduction on three nontarget native species of saturniid moths. Conservation Biology 14:1796-1806.

Canadian Forest Service (CFS). 1973. Forest insect and disease conditions in Ontario. Bulletin No. 3 (August-September 1973). L.L. McDowall and W.L. Sippell (eds.) 10 pp.

Canadian Forestry Service (CFS). 1985. Forest insect and disease conditions in Ontario, 1985. Bulletin No. 3. Compiled by M.J. Applejohn and G.M. Howse. Government of Canada. 32 pp.

Coffelt, M.A., and P.B. Schultz. 1993. Host plant suitability of the orange-striped oakworm (Lepidoptera: Saturniidae). Journal of Environmental Horticulture 11:182-186.

COSEWIC. 2009. COSEWIC assessment and status report on the Virginia Goat’s-rue Tephrosia virginiana in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 31 pp.

COSEWIC. 2019. COSEWIC assessment and status report on the Reversed Haploa Moth Haploa reversa in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 40 pp.

COSEWIC. 2021. Guidelines for recognizing designatable units. Appendix E4 in COSEWIC Operations and Procedures Manual, revised November 2021. Committee on the Status of Endangered Wildlife in Canada, Environment and Climate Change Canada, Ottawa, Ontario.

Didham, R.K., Y. Basset, C.M. Collins, S.R. Leather, N.A. Littlewood, M.H.M. Menz, J. Müller, L. Packer, M.E. Saunders, K. Schönrogge, A.J.A Stewart, S.P. Yanoviak, and C. Hassall. 2020. Interpreting insect declines: seven challenges and way forward. Insect Conservation and Diversity 13:103-114.

Dowsley, M. 2021. Personal communication to L. Kohalmi. Associate Professor. Department of Anthropology and Department of Geography and the Environment, Lakehead University.

Elkinton, J.S., and G.H. Boettner. 2012. Benefits and harm caused by the introduced generalist tachinid, Compsilura concinnata, in North America. BioControl 57:277-288.

Environmental Registry of Ontario. 2023. Decision on proposed amendments to the Greenbelt Area boundary regulation. https://ero.Ontario.ca/notice/019-6217. [accessed February 13, 2023].

Ferguson, D.C. 1971. Bombycoidea: Saturniidae, Citheroniinae and Hemileucinae. Part I. Moths of America North of Mexico, Fascicle 20.2B. E.W. Classey Ltd. and R.B.D. Publications, London, England.

Government of Ontario. 2021. Ontario population projections. https://www.Ontario.ca/page/Ontario-population-projections [accessed September 2, 2023].

Hanski, I. 1982. Dynamics of regional distribution: the core and satellite species hypothesis. Oikos 38: 210-221.

Henne, D.C. 2004. Parasitoid survey of Anisota virginiensis (Lepidoptera: Saturniidae) at Belair, Manitoba from 1989-1999. Proceedings of the Entomological Society of Manitoba 60:5-10.

Henne, D.C. 2021. Personal communication to L. Kohalmi. Entomologist, Manitoba.

Henson, B.L., and K.E. Brodribb. 2005. Great Lakes Conservation Blueprint for Terrestrial Biodiversity Volume 2: Ecodistrict Summaries. Nature Conservancy of Canada. 351 pp.

Hessel, S.A. 1976. A preliminary scan of rare and endangered Nearctic moths. Atala 4:19-21.

Hiratsuka, Y. 1987. Forest tree diseases of the prairie provinces. Canadian Forest Service Northern Forestry Centre, Edmonton, Alberta. Inv. Rep. NOR-X-286.

Hubley, Brad. 2020. Personal communication to L. Kohalmi. Entomology Collection Manager. Department of Natural History. Royal Ontario Museum, Toronto, Ontario.

iNaturalist. 2023. Anisota finlaysoni observations https://www.inaturalist.org/taxa/59918-Anisota-finlaysoni [accessed September 25, 2023].

IUCN (International Union for the Conservation of Nature) Standards and Petitions Committee. 2019. Guidelines for Using the IUCN Red List Categories and Criteria. Version 14.0. Prepared by the Standards and Petitions Subcommittee in August 2019.

IUCN (International Union for the Conservation of Nature). 2001. IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. Gland, Switzerland and Cambridge, U.K. (and subsequent updates). https://www.iucnredlist.org [accessed November 2020].

Johnson, W.T., and H.H. Lyon. 1976. Insects that feed on trees and shrubs: an illustrated practical guide. Cornell University Press. 464 pp.

Kline, V.M. 1997. Orchards of oak and a sea of grass. Pp. 3-21, in S. Packard and C.F. Mutel (eds.). The Tallgrass Restoration Handbook. Island Press.

Kohalmi, L. 2023. Personal data (2007-2019) on observations, hybridization, phenology, and genetics of Finlayson’s Oakworm (Anisota finlaysoni) and Orange-striped Oakworm (Anisota senatoria). Information was communicated during the preparation of this status report (2023). Independent lepidopterist, Ontario.

Krieg, A., and G.A. Langenbruch. 1981. Susceptibility of arthropod species to Bacillus thuringiensis. Pp. 837-896, in H.D. Burges (ed.). Microbial Control of Pests and Plant Diseases 1970-1980. Academic Press, London.

Lambert, S. 2020. Email correspondence to L. Kohalmi. August 2020. Manager, Resource Conservation, Thousand Islands National Park, Parks Canada, Mallorytown, ON.

Linton, J. 2015. Recovery Strategy for the Mottled Duskywing (Erynnis martialis) in Ontario. Ontario Recovery Strategy Series. Prepared for the Ontario Ministry of Natural Resources and Forestry, Peterborough, Ontario. V + 38 pp.

MacAloney, H.J., and H.G. Ewan. 1964. Identification of hardwood insects by type of tree injury, North-Central Region. Lake States Experiment Station, St. Paul, Minnesota. U.S. Forest Service Research Paper LS-11). 70 pp.

McGugan, R.M. 1958. Forest Lepidoptera of Canada recorded by the Forest Insect Survey. 1. Papilionidae to Arctiidae. Forest Biology Division, Canada Department of Agriculture, Publication 1034, Ottawa.

Meating, J.H., G.M. Howse, and J.J. Churcher. 1990. Gypsy Moth in Ontario. Report prepared for the Eighteenth Annual Forest Pest Control Forum, Ottawa, November 20-22, 1990.

Miller, J.C. 1990. Field assessment of the effects of a microbial pest control agent on nontarget Lepidoptera. American Entomologist. Summer 1990:135-139.

Miller, J.C. 1992. Effects of a microbial insecticide, Bacillus thuringiensis kurstaki, on nontarget Lepidoptera in a spruce budworm-infested forest. Journal of Research on the Lepidoptera. 29: 267-276.

Ministry of Natural Resources and Forestry (MNRF). 2023. Lymantria dispar dispar (LDD) moth. https://www.Ontario.ca/page/lymantria-dispar-dispar-ldd-moth#section-0 [accessed February 13, 2023].

Natural Resources Canada – Canadian Forest Service. 1988. A review of important forest insect and disease problems in the Brockville District of Ontario, 1950-1980. Compiled by L.S. MacLeod, D.C. Constable, V. Jansons, and W.A. Ingram. Forestry Canada, Ontario Region. Government of Canada.127 pp.

Natural Resources Canada – Canadian Forest Service. 1991a. A review of important forest insect and disease problems in the Napanee District of Ontario, 1950-1980. Compiled by D. Constable, W.D. Biggs, W.A. Ingram, B.E. Smith, E. Czerwinski, and P. Bolan. Forestry Canada, Ontario Region. Government of Canada. 191 pp.

Natural Resources Canada – Canadian Forest Service. 1991b. A review of important forest insect and disease problems in the Niagara District of Ontario, 1950-1980. Compiled by W.D. Biggs D.C. Constable, C.G.Jones and P.M. Bolan. Forestry Canada, Ontario Region. Government of Canada. 33 pp.

Natural Resources Canada. 2015. Two-lined chestnut borer (Agrilus bilineatus [(Weber\) fact sheet. Website: https://tidcf.nrcan.gc.ca/en/insects/factsheet/284 [accessed September 15, 2019].

NatureServe. 2023. NatureServe Explorer 2.0. Anisota finlaysoni. https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.118613/Anisota_finlaysoni [accessed November 11, 2023].

Niagara Region 2041 Growth Strategy. 2016. Presentation “How We Grow” on https://www.niagararegion.ca/2041/pdf/mcr-pic3-boards.pdf [accessed 2021].

Niagara Region Potential Resource Areas-Stone. 2015. Niagara Region Official Plan. https://www.niagararegion.ca/living/icp/pdf/2015/schedules/official-plan-schedule-d1.pdf [accessed March 2021].

Nowacki, G.J., and M.D. Abrams. 2008. The demise of fire and “mesophication” of forests in the eastern United States. Bioscience (58) 2:123-138.

Nystrom, K.L., and I.M. Ochoa. 2006. Insects and mites associated with Ontario forests: Classification, common names, main hosts, and importance. Natural Resources Canada, Canadian Forest Service Information Report GLC-X-7. 98 pp.

Oak, S.W. 2002. Native diseases and insects that impact oaks. Chapter 6 in Oak Forest Ecosystems: Ecology and Management for Wildlife. W.J. McShea, and W.M. Healy (eds.). The Johns Hopkins University Press. xiii + 432 pp.

OMNR (Ontario Ministry of Natural Resources). 1981. Results of forest insect and disease surveys in the Central Region of Ontario, 1980. M.J. Applejohn, H.J. Weir, and C.A. Barnes (eds.). 33 pp.

OMNR (Ontario Ministry of Natural Resources). 2007. Forest Health Conditions in Ontario, 2006. T. Scarr, A. Hopkin, and J. Pollard (eds.). Queen’s Printer for Ontario. vi + 81 pp.

Ontario Ministry of Natural Resources and Forestry. 2023. Lymantria dispar dispar (LDD) moth. https://www.Ontario.ca/page/spongy-moth#section-0[accessed February 13, 2023].

Packer, L. 1991. The status of two butterflies, Karner Blue (Lycaeides melissa samuelis) and Frosted Elfin (Incisalia irus), restricted to oak savannah in Ontario. Pp. 245-271, in G.W. Allen, P.F.J. Eagles, and S.W. Price (eds.). Conserving Carolinian Canada. University of Waterloo Press.

Packer, L. 1994. The Extirpation of the Karner Blue Butterfly in Ontario. Pp. 143-151, in D.A. Andow, R.J. Baker, and C.P. Lane (eds.). Karner Blue Butterfly: A Symbol of a Vanishing Landscape. Minnesota Agricultural Experiment Station (Miscellaneous Publication series), St. Paul, Ontario.

Peigler, R.S. 1994. Catalog of parasitoids of Saturniidae of the world. Journal of Research on the Lepidoptera. 33:1-121.

Pohl, G.R., B. Patterson, and J.P. Pelham. 2016. Annotated taxonomic checklist of the Lepidoptera of North America, North of Mexico. Working paper published online by the authors at ResearchGate.net 766 pp.

Rastall, K., V. Kondo, J.S. Strazanc, and L. Butler. 2003. Lethal effects of biological insecticide applications on nontarget Lepidopterans in two Appalachian forests. Environmental Entomology 32(6):1364-1369.

Reardon, R.C., and K. Haissig. 1984. Efficacy and field persistence of Bacillus thuringiensis after ground application to balsam fir and white spruce in Wisconsin. Canadian Entomologist 116:153-158.

Riotte, J.C.E., and R.S Peigler 1980. A revision of the American genus Anisota (Saturniidae). Journal of Research on the Lepidoptera.19:101-180.

Rodger, L. 1998. Tallgrass Communities of Southwestern Ontario: A Recovery Plan. Prepared for World Wildlife Fund and the Ontario Ministry of Natural Resources and Forestry. February 1998. pp. 78.

Rose, A.H., and O.H. Lindquist. 1982. Insects of eastern hardwood trees. Department of the Environment, Canadian Forestry Service, Forestry Technical Report 29. Ottawa. 304 pp.

Sajan, B. 1981. Results of forest insect and disease surveys in the Eastern region of Ontario, 1980. Great Lakes Forest Research Centre and Ontario Ministry of Natural Resources, Sault Ste. Marie, Ontario. 24 pp. https://osdp-psdo.Canada.ca/dp/en/search/metadata/NRCAN-CFS-1-32268 [accessed September 25, 2023].

Sajan, R.J. 1982. Results of forest insect and disease surveys in the Eastern region of Ontario, 1981. Great Lakes Forest Research Centre and Ontario Ministry of Natural Resources. 28 pp. https://cfs.nrcan.gc.ca/publications?id=34598 [accessed September 25, 2023].

Sajan, R.J. 1983. Results of forest insect and disease surveys in the Eastern region of Ontario, 1982. Great Lakes Forest Research Centre and Ontario Ministry of Natural Resources. 30 pp. https://osdp-psdo.Canada.ca/dp/en/search/metadata/NRCAN-CFS-1-34603 [accessed September 25, 2023].

Schmidt, C. 2023. Personal communication to J. Heron. Research Scientist, Agriculture and Agri-Food Canada. Ottawa Research and Development Centre. Ottawa, Ontario.

Seligy, V.L., R.W. Beggs, J.M. Rancourt, and A.F. Tayabali. 1997. Quantitative bioreduction assays for calibrating spore content and viability of commercial Bacillus thuringiensis insecticides. Journal of Industrial Microbiology and Biotechnology 18:370-378.

Singh, T., and J. Satyanarayana. 2009. Insect Outbreaks and Their Management, in R. Peshin and A.K. Dhawan (eds.) Integrated Pest Management: Innovation-Development Process. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-8992-3_13 [accessed February 24, 2023].

St. Laurent, R. 2020. Email and verbal communication with L. Kolmani. Ph.D. student, University of Florida. Gainsville, Florida.

Statistics Canada. 2022. Land use, Census of Agriculture. https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=3210040601&pickMembers%5B0%5D=1.1099&cubeTimeFrame.startYear=2011&cubeTimeFrame.endYear=2016&referencePeriods=20110101%2C20160101 [accessed July 14, 2022].

Swengel, S.R., D. Schlicht, F. Olsen, and A.B. Swengel. 2010. Declines of prairie butterflies in the midwestern USA. Journal of Insect Conservation 15:32-339.

Symbiota Collections of Arthropods Network (SCAN). 2020. https://scan-bugs.org/portal/taxa/index.php?taxon=Anisota+finlaysoni&formsubmit=Search+Terms [accessed September 23, 2020].

Taekema, D. 2019. ‘City planners warn Bill 66 could ‘incentivize’ development in the Greenbelt’. CBC News-Hamilton. 17 January 2019. https://www.cbc.ca/news/Canada/hamilton/city-planners-warn-bill-66-could-incentivize-development-in-the-greenbelt-1.4981244 [accessed 28 September 2020].

Toronto Entomologists’ Association (TEA). 2020. Ontario Moth Atlas. https://www.ontarioinsects.org/moth/index.html [accessed August 25, 2020].

Tuskes, P.M., J.P. Tuttle, and M.M. Collins. 1996. The wild silk moths of North America: a natural history of the Saturniidae of the United States and Canada. Ithaca, NY and London: Cornell University Press. iv + 250 pp.

Van Wieren, J. 2021. Personal communication to L. Kohalmi. Park Ecologist. Thousand Islands National Park, Parks Canada Agency, Ontario.

Vilas-Boas, L.A., G.F.L.T. Vilas-Boas, H.O. Saridakis, M.V.F. Lemos, D. Lereclus, and O.M.N. Arantes. 2000. Survival and conjugation of Bacillus thuringiensis in a soil microcosm. FEMS Microbiology Ecology 31:255-259.

Wagner, D.L. 2012. Moth decline in the northeastern United States. News of the Lepidopterists’ Society 54:52-56.

War, A.R, M.G. Paulraj, T. Ahmad, A.A. Buroo, B. Hussain, S. Ignacimuthu, and H.C. Shaarmal. 2012. Mechanisms of Plant Defense against Insect Herbivores. Plant Signalling and Behavior 7(10):1306-1320.

Watson and Associates Economists Ltd. 2020. Population, Housing and Employment Projections Study, County of Frontenac. (https://www.frontenaccounty.ca/en/government/resources/Documents/Frontenac-County-Population-Housing-and-Employment-Projections-2016-to-2046-Final-Report-2020.pdf) [accessed September 20, 2023].

Williams, P.A., J.W. McNeil, K.W. Gottschalk, and R.A. Haack. 2013. Managing an oak decline crisis in Oakville, Ontario: Lessons learned. Proceedings of the 18th Central Hardwoods Forest Conference: pp.192-207.

Biographical summary of report writers

Dr. Don Henne holds a B.Sc. in Agriculture (Major: entomology) and a M.Sc. in entomology from the University of Manitoba, as well as a Ph.D. in entomology from Louisiana State University. His research interests include insect biodiversity and conservation, population ecology, spatial and ecological statistics, and host-parasitoid interactions. He is currently employed as an entomologist in the private sector.

Lester Kohalmi has a B.Sc. (biology and chemistry) and a B.A. (theatre arts) from the Department of Biology and the Department of Fine Arts, respectively, at York University. He has an M.Sc. with a thesis on genetics and speciation in the genus Hyalophora (Lepidoptera:Saturniidae) also from York University. He has written scientific publications on Lepidoptera and yeast molecular genetics. He is also a professional photographer and has edited books and authored newspaper and magazine articles.

Albert Tomchyshyn is an HBSc graduate from the University of Toronto, Mississauga, with a major in biology and minors in mathematics and environmental management. He is currently the secretary for the Toronto Entomologists’ Association and worked on the Association’s Ontario Moth and Butterfly atlases. His research includes a project that evaluated milkweed pollinator richness and abundance and was presented at the Entomological Society of Ontario’s Annual General Meeting in 2019.

Collections examined

The following collections were queried for Finlayson’s Oakworm Moth

• American Museum of Natural History (AMNH), 200 Central Park West, New York, New York 10024-5102
• Buffalo Museum of Science, 1020 Humboldt Parkway, Buffalo, New York 14211 (Paige Langle)
• Canadian Museum of Nature, The Natural Heritage Campus, 1740 Pink Road, Gatineau, Quebec, J9J 3N7 (Robert Anderson)
• Canadian National Collection (CNC) of Insects, Arachnids and Nematodes, Agriculture and Agri-Food Canada, K.W. Neatby Building, 960 Carling Avenue, Ottawa, Ontario K1A 0C6 (Don Lafontaine)
• Great Lakes Forestry Centre (NRC-FRS), Natural Resources Canada, 1219 Queen Street East, Sault Ste Marie, Ontario P6A 2E5 (Kevin Barber)
• Lyman Entomological Museum, McGill University, 21111 Lakeshore Road, Ste-Ann-de-Bellevue, Quebec H9X 3V9 (Stephanie Boucher)
• Michigan State University, Albert J. Cook Arthropod Research Collection, 426 Auditorium Road, East Lansing, Michigan 48824 (online database search - https://doi.org/10.15468/dl.h8pebv)
• Milwaukee Public Museum Invertebrate Zoology Collection (MPM), 800 West Wells Street, Milwaukee, Wisconsin 53233 (online database search)
• Natural History Museum (NHM), Cromwell Road, London, England SW7 5BD (online database search)
• Northern Forestry Centre (NRC-FRS), Natural Resources Canada, 5320-122nd Street, Edmonton, Alberta T6H 3S5 (Greg Pohl)
• Royal Alberta Museum, 12845-102nd Avenue, Edmonton, Alberta T5N 0M6 (Tyler Cobb)
• Royal British Columbia Museum, 675 Belleville Street, Victoria, British Columbia V8W 9W2 (online database search)
• Royal Ontario Museum (ROM), 100 Queen’s Park, Toronto, Ontario M5S 2C6 (Brad Hubley)
• Smithsonian National Museum of Natural History (USNM), 10th Street and Constitution Avenue, Washington, D.C. 20560 (online database search)
• Spencer Entomological Collection, Beaty Biodiversity Museum, University of British Columbia, 2212 Main Hall, Vancouver, British Columbia V6T 1Z4 (online database search)
• Strickland Entomological Museum, University of Alberta, Edmonton, Alberta T6G 2E9 (online database search)
• Texas A and M University, Department of Entomology, TAMU 2475, College Station, Texas 77843-2475 (James McDermott)
• The Manitoba Museum, 190 Rupert Avenue Winnipeg, Manitoba R3B 0N2 (Randall Mooi)
• Toronto Entomologists’ Association (TEA) Moth Atlas (online database search)
• University of Georgia Collection of Arthropods (UGCA), Natural History Museum Building, Athens, Georgia 30602-7882 (online database search)
• University of Guelph, Guelph, Ontario N1G 2W1 (Steve Marshall)
• University of Minnesota Insect Collection (UMSP), Department of Entomology, 219 Hodson Hall, 1980 Folwell Avenue, University of Minnesota, St. Paul, Minnesota 55108 (online database search)
• Western University, Department of Biology, Biological and Geological Sciences Building, London, ON N6A 5B7 (Nina Zitani)
• Yale Peabody Museum of Natural History (PMNH), 170 Whitney Avenue, New Haven, Connecticut 06511 (online database search)

Appendix 1. Subpopulations of Finlayson’s Oakworm Moth (Anisota finlaysoni) based on information from museum specimens, observations, written documentation and online sources.

¹ Records reported in Riotte and Peigler (1980) are likely localities reported by the Forest Insect Survey (FIS) in McGugan (1958). The whereabouts of these specimens or records are unknown and some records may be lost (Pohl pers. comm. 2020).

² Museums where specimens are housed and/or literature sources: CNC (Canadian National Collection), DM (Denver Museum of Nature and Science), FIDS (Forest Insect and Disease Survey), FIS (Forest Insect Survey, Canadian Department of Agriculture), MPM (Milwaukee Public Museum), MSU (Michigan State University), ON FHC (Forest Health Conditions in Ontario, published by the Ontario Ministry of Natural Resources and Forestry) (OMNR 2007), ROM (Royal Ontario Museum), TEA (Toronto Entomologists’ Association), UGA (University of Georgia), UWO (Western University), YPM (Yale Peabody Museum).

³ Historical: Recent field information verifying the continued existence of the subpopulation is lacking, based on historical collection data, but without recent field survey work. The subpopulation may have become extirpated due to general habitat loss or degradation of the environment in the area. Historical status is typically applied to an occurrence that has not been reconfirmed for 20 years or more; may also indicate occurrences with imprecise site collection information such that it may be difficult or impossible to determine whether subsequent observations are of the same occurrence (modified from NatureServe 2023).

⁴ Extant: The species is known or thought very likely to currently occur in the area, which encompasses localities with current or recent (< 20 years) records where suitable habitat remains. Extant subpopulations are included in the calculation of EOO.

Appendix 2. Threats assessment of the Finlayson’s Oakworm Moth (Anisota finlaysoni) in Canada. The classification below is based on the IUCN-CMP (international union for the conservation of nature–conservation measures partnership) unified threats classification system. For a detailed description of the threat classification system, see the cmp web site (CMP 2010). Threats may be observed, inferred, or projected to occur in the near term. Threats are characterized here in terms of scope, severity, and timing. Threat “impact” is calculated from scope and severity. For information on how the values are assigned, see master et al. (2009) and footnotes to this table.

Scientific name:

Finlayson’s Oakworm Moth (Anisota finlaysoni)

Assessment date:

Dec 20, 2021

Assessors:

Les Kohalmi (report writer), Don Henne (report writer), Syd Cannings (CWS and Arthropods SSC), Colin Jones (ON Rep. and Arthropods SSC), David McCorquodale (Arthropods Co-chair), Jeff Ogden (Arthropods SSC), Joanna James (COSEWIC Secretariat), Jennifer Heron (Arthropods Co-chair).

References:

See Appendix 1 (Subpopulations of Finlayson’s Oakworm Moth (Anisota finlaysoni) based on information from museum specimens, observations, written documentation and online) and Appendix 3 (Federal and provincial forest inventory reports for Finlayson’s Oakworm Moth (Anisota finlaysoni).

Assigned overall threat impact:

High

Impact adjustment reasons:

There is potential overlap in scope and severity between threats (for example, impacts of Spongy Moth defoliation, spraying to control larval outbreaks, low detectability of the moth), and for many of the sites/subpopulations, the available information is qualitative. Given the low detectability of the moth, there are likely additional undocumented subpopulations within potential habitat. The threat was adjusted from Very high to High to account for these unknowns.

Overall, threat comments

The moth may be present at low abundance at some sites, and may be detected within the next ten years, although habitat quality and quantity are declining.

¹ Impact – The degree to which a species is observed, inferred, or suspected to be directly or indirectly threatened in the area of interest. The impact of each stress is based on Severity and Scope rating and considers only present and future threats. Threat impact reflects a reduction of a species population or decline/degradation of the area of an ecosystem. The median rate of population reduction or area decline for each combination of scope and severity corresponds to the following classes of threat impact: very high (75% declines), high (40%), medium (15%), and low (3%). Unknown: used when impact cannot be determined (for example, if values for either scope or severity is unknown).

² Scope – Proportion of the species that can reasonably be expected to be affected by the threat within 10 years. Usually measured as a proportion of the species’ population in the area of interest. (Pervasive = 71 to 100%; Large = 31 to 70%; Restricted = 11 to 30%; Small = 1 to 10%)

³ Severity – Within the scope, the level of damage to the species from the threat that can reasonably be expected to be affected by the threat within a 10-year or three-generation timeframe. Usually measured as the degree of reduction of the species’ population (Extreme = 71 to 100%; Serious = 31 to 70%; Moderate = 11 to 30%; Slight = 1 to 10%).

⁴ Timing – High = continuing; Moderate = only in the future (could happen in the short term [< 10 years or 3 generations]) or now suspended (could come back in the short term); Low = only in the future (could happen in the long term) or now suspended (could come back in the long term); Insignificant/Negligible = only in the past and unlikely to return, or no direct effect but limiting.

Appendix 3. Federal and provincial forest inventory reports for Finlayson’s Oakworm Moth (Anisota finlaysoni).

The study of forest insects and their impacts on Canada’s forests became a priority in the late 1940s, and for the past 80 years there have been ongoing surveys and programs led by the Canadian Forestry Service to monitor forest insects (Natural Resources Canada 2021). From the late 1940s until the mid-1990s, general Lepidoptera (and other insect) surveys collected and reared live larvae to the adult stage for identification; the specimens were tallied and deposited in museums. This work began as part of the Forest Insect and Disease Surveys (FIDS) initiated in 1936 by the Dominion Entomological Laboratory and coordinated from Ottawa until 1944, when Ontario was divided into ‘northern’ and ‘southern’ Ontario for the purpose of these surveys. In 1945, personnel from Ottawa continued surveys south of the Algonquin Park and Parry Sound Forest districts, while personnel from the Forest Insect Laboratory in Sault Ste. Marie carried out surveys in the area to the north. In 1950 the Sault Ste. Marie laboratory became responsible for reporting insect survey results for all of Ontario. The results of these insect and disease surveys were reported in the Annual Report of the Forest Insect and Disease Survey (FIDS) published by Forestry Canada. Beginning in 1948, the annual district and regional reports were prepared by FIDS technicians (Rangers) in Sault Ste. Marie. Since 2006, the Ontario Ministry of Natural Resources and Forestry Has published an annual Forest Health Conditions in Ontario report (OMNR 2007).

Most of the historical sampling effort for Finlayson’s Oakworm Moth has focused on recording distribution and abundance to assess the defoliation risk to oak trees.

The following are Finlayson’s Oakworm Moth data summarized from Forest Insect and Disease Survey reports (see Information Sources). Moth abundance data was typically not enumerated, and many observations are based on subjective defoliation observations. These reports use the following terms interchangeably: oakworms, Shorthorned Oakworm, Anisota finlaysoni and Orange-striped Oakworm Moth, Anisota senatoria.

FIDS napanee 1950-1980 summary (NRC-CFS 1991a)

Records prior to 1970 were identified as A. senatoria (=A. finlaysoni) but the localities are within the current range of A. finlaysoni. Defoliation by these insects seldom causes mortality of the host; however, weakened trees are subject to attack by secondary insects and diseases. Moderate-to-severe defoliation was reported for most of the periods from 1951 to 1967.

1950 None reported.

1951 A. senatoria severely defoliated oak along the Trent River in south Hastings County.

1952 Heavy infestations occurred in Sidney, Thurlow, Richmond and Sophiasburg Townships. Complete defoliation of oak was recorded and the defoliator was identified as A. senatoria.

1953 White and Bur Oak in Richmond and Camden Townships suffered approximately 15% defoliation by A. senatoria.

1954-1955 A. senatoria caused varying degrees of defoliation of Bur Oak in Portland, Kingston, and North and South Fredericksburgh Townships.

1956 A. senatoria caused almost complete defoliation of open-grown White Oak trees in pastures and woodlots west of Shannonville in Tyendinaga Township.

1957 The heavy infestation recurred in Tyendinaga Township and 100% defoliation of White Oak was recorded on 9 ha of White Oak in Ameliasburgh and Sophiasburgh Townships.

1958 Medium-to-heavy infestations of A. senatoria were found throughout Sidney, Sophiasburgh and North and South Fredericksburgh Townships.

1959 Heavy infestations recurred in Sidney, Thurlow, Tyendinaga, Hilliard and Ameliasburgh Townships.

1960 Pockets of heavy infestations recurred through the entire district.

1961 Populations declined compared with those found in 1960 but small pockets of severely defoliated oak were observed in Sidney, Thurlow, Tyendinaga and Hallowell Townships.

1962 Severe defoliation was recorded in Tyendinaga Township, but the insect was not reported elsewhere in the district.

1963 Pockets of severe defoliation by A. senatoria were recorded in Thurlow, Sidney and Tyendinaga Townships.

1964 Small numbers were found in Tyendinaga and Thurlow Townships.

1965 A few A. senatoria were found in Tyendinaga Township.

1966 None reported.

1967 A small group of Bur Oak trees suffered 100% defoliation in Sidney Township.

1968 One colony found (no location given).

1969 None reported.

1970 A. finlaysoni was reported in high numbers on bur and White Oak in the Kingston and Napanee areas.

1971 The small infestation near Kingston expanded to cover an area 5 km wide from Kingston to Belleville. Within this area individual trees were completely defoliated by A. finlaysoni.

1972 The infestation in the Kingston-Belleville area encompassed 518 km² where small stands and individual trees were completely defoliated. Moderate-to-severe defoliation also occurred in Hilliard Township, Prince Edward County.

1973 Moderate-to-severe defoliation occurred in Richmond, Ernestown and Kingston Townships and on the western part of Howe Island.

1974 None reported.

1975 Scattered colonies were observed on roadside trees near Kingston and Gananoque.

1976 Occasional colonies noted on roadside trees near Gananoque.

1977-1979 None reported.

1980 Open-grown Bur Oak suffered 100% defoliation along roads in Richmond, Tyendinaga, Thurlow and Sophiasburgh Townships.

FIDS brockville 1950-1980 (NRC-CFS 1988)

1950-1972 None reported.

1973 Small populations were observed in Front of Leeds and Lansdowne Townships near Gananoque.

1974 None reported.

1975 Scattered colonies along roadsides near Gananoque.

1976 Occasional colonies on oak near Gananoque

1977-1980 None reported.

FIDS Niagara 1950-1980 summary (NRC-CFS 1991b)

1950-1970 None reported.

1971 Moderate defoliation to Bur Oak was found in the Grimsby area and small pockets of light damage were found in the Dunnville area.

1972 Severe defoliation to scattered White Oak was recorded in Seneca, Grimsby and Gainsborough Townships.

1973 Moderate-to-severe defoliation of individual open-growing White Oak was observed in Grimsby Township.

1974-1980 None reported.

FIDS niagara 1950-1980 summary (NRC-CFS 1991b)

Originally identified as A. senatoria (=A.finlaysoni)

1950-1955 None reported.

1956 A light infestation was found in Bertie Township.

1957 Infestation levels increased near Dunnville.

1958-1959 Light infestations were present in the Dunnville area.

1960-1961 A medium infestation was found in Seneca Township and a light infestation in Wainfleet Township.

1962-1963 None reported.

1964 Severe defoliation was observed in Bertie Township.

1965-1966 none reported.

1967 A medium infestation was present in Canborough and Caistor Townships.

1968-1980 None reported.

FIDS – Ontario central region 1980 (OMNR 1981)

After declining to low levels in 1979, abundance increased in 1980. Small pockets of heavy infestation occurred on small numbers of open growing White Oak (Quercus alba) trees on the western outskirts of Brantford and in the Breslau-Conestogo area of Cambridge District. Medium infestations were observed on hedgerow trees south of Milton in the Cambridge District and small numbers of larvae were noted on a few ornamentals in the Maple District north of Toronto.

FIDS – Ontario eastern region 1980 (SAJAN 1981)

There was a marked increase in the defoliation caused by Finlayson’s Oakworm Moth in the central portion of the Napanee District in 1980. Open-grown Bur Oak (Quercus macrocarpa) were 100% defoliated east of the town of Napanee along Highway 401, west of Deseronto throughout the Tyendinaga Indian Reserve, and north of Belleville in Thurlow Township. In the Green Point area of Sophiasburg Township, Bur Oaks were completely denuded of foliage and the immature larvae migrated to nearby Shagbark Hickory (Carya ovata) trees. These hickories were lightly defoliated. The larvae could not survive on them and were unable to complete their life cycle. Light defoliation was detected across the central portion of Wolfe Island on open-grown fencerow trees.

FIDS Ontario 1973 (CFS 1973)

Oak trees were defoliated in parts of southwestern Ontario, particularly in the southern parts of Halton and Wentworth counties and in the northern part of the Niagara Peninsula. Elsewhere, scattered areas of light and moderate defoliation were observed. In the southeastern region, populations declined from 1972 levels; however, pockets of moderate-to-heavy defoliation were noted near Napanee and Kingston.

FIDS Ontario 1985 (CFS 1985)

Finlayson’s Oakworm Moth caused 10% to 100% defoliation of open-grown White and Bur Oak in the town of Milton and in Flamborough and Blenheim Townships, Cambridge District.

Ontario forest health conditions 2006 (OMNR 2007)

An infestation of Finlayson’s Oakworm Moth was recorded on Northern Red Oak trees near Walsh Station, Norfolk County, Aylmer District. Defoliation reached 100% on juvenile trees within the stand while larger, mature trees sustained moderate-to-severe defoliation. Larvae were present and active well into early September.

Appendix 4. Field summary report on Finlayson’s Oakworm Moth (Anisota finlaysoni riotte) by Lester Kohalmi, October 20, 2021. This report summarizes the fieldwork completed during the preparation of the COSEWIC status report on Finlayson’s Oakworm Moth (Anisota finlaysoni). Please contact the COSEWIC secretariat for a copy of this report.