Pacific Sandpirate (Lasiopogon pacificus): COSEWIC assessment and status report 2024

Official title: COSEWIC assessment and status report on the Pacific Sandpirate (Lasiopogon pacificus) in Canada

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

Special Concern

2024

COSEWIC assessment summary

Assessment summary – May 2024

Common name

Pacific Sandpirate

Scientific name

Lasiopogon pacificus

Status

Special Concern

Reason for designation

In Canada, this robber fly’s distribution is limited to openings in early to mid-successional forest in British Columbia’s Lower Mainland. The larval stage is found only in sandy or gravelly soils. There are nine subpopulations documented, three of which are known only from historical records. Additional subpopulations probably exist but the total number is likely fewer than 20. The species’ habitat is at risk from development and degradation from multiple causes.

Occurrence

British Columbia

Status history

Designated Special Concern in May 2024.

COSEWIC executive summary

Pacific Sandpirate

Lasiopogon pacificus

Wildlife species description and significance

Pacific Sandpirate (Lasiopogon pacificus) is a medium-sized (~1 cm) robber fly (family Asilidae). Distinguishing characters include a broad gap between the eyes on top of the head, a bushy black mustache, three dark stripes running down the top of the thorax, abdominal segments with straight rings of dark and light, and two opposable stocky wedge-shaped claspers on the tip of the male abdomen.

Pacific Sandpirate is one species in a group of robber flies in which ecological niche specialization has helped facilitate diversification and coexistence. Robber flies are popular among amateur naturalists, with a growing number of internet-based resources and field guides available.

Aboriginal (Indigenous) knowledge

All species are significant and are interconnected and interrelated. There is no species-specific Aboriginal Traditional Knowledge in the report.

Distribution

Pacific Sandpirate’s global range is along the Pacific coast from southwestern British Columbia (BC) to southern Oregon. In Canada it is known only from fewer than 10 subpopulations along the lower Fraser River Valley in BC.

Habitat

Pacific Sandpirate inhabits early- to mid-successional forest within the Coastal Western Hemlock biogeoclimatic zone, usually in hilly dry forest openings at low elevations (< 300 m asl) not far from streams. Adults perch on bare sand or low rocks and logs in exposed sunny patches during the day and shelter overnight in low shrubbery. Eggs, larvae, and pupae live underground in sandy soil. Patchy disturbance from natural (for example, winds, floods, or erosion) or anthropogenic (for example, tree removal, trail building) causes can help maintain a constellation of small open areas where subpopulations of Pacific Sandpirate occur.

Biology

This species develops through complete metamorphosis, that is, from egg to larva to pupa to adult. The generation time is at least two years. Adults emerge for a few weeks in late spring (mainly late May and June). Adults are likely generalist predators that feed mainly on other small flies, true bugs, and adult aquatic insects, while larvae are likely predators of beetle larvae. Most adult individuals stay within a home range of only a few dozen square metres, with lifetime net dispersal usually amounting to less than 1 km.

Population sizes and trends

Population size and trends of Pacific Sandpirate in Canada are unknown. Recent surveys focused on locating extant subpopulations and recording habitat information. The primary survey method has consisted of wandering transects during the adult flight period. There are 35 specimens or observations from Canada, of which 12 are from the last 10 years. Of the six subpopulations that have been proven extant with recent records, five were newly documented during recent search effort. Three subpopulations are known from historical records only.

Threats

The Canadian range of Pacific Sandpirate has been subject to extensive waves of resource extraction, conversion of forest to agriculture, and urban development, which have reduced and fragmented potential habitat. Some of the most important threats to Pacific Sandpirate include residential and commercial development, logging, pollution, and changes to habitat. Efforts to grow tracts of forest in the Coastal Western Hemlock biogeoclimatic zone may have interrupted some of the disturbance processes that once maintained a steady patchwork of early- and mid-successional forest communities suitable for Pacific Sandpirate.

Protection, status, and recovery activities

Pacific Sandpirate has not been assessed by COSEWIC, is not listed under SARA, and is not afforded protection under legislation in British Columbia. The species is not ranked globally or in the USA. It is ranked Imperilled in Canada and BC (N2/S2) and is red-listed by the B.C. Conservation Data Centre. Most of the species’ range in Canada falls within local government jurisdictions and provincial public land.

Technical summary

Lasiopogon pacificus

Pacific Sandpirate

Asile de la côte Ouest

Indigenous names: none known

Range of occurrence in Canada: British Columbia

Demographic information:

Generation time (usually average age of parents in the population)

Approximately 2 years

Based on size distribution of larvae in related species

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

Unknown

Insufficient data

[Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 3 years [or 1 generation; whichever is longer up to a maximum of 100 years]

Unknown

Insufficient data

Observed, estimated, or projected] 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]

Unknown

Insufficient data

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

Unknown

Insufficient data

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

Unknown

Insufficient data

Are the causes of the decline clearly reversible?

Unknown

Insufficient data

Are the causes of the decline clearly understood?

Unknown

Insufficient data

Are the causes of the decline clearly ceased?

Unknown

Insufficient data

Are there extreme fluctuations in number of mature individuals?

Unknown

Insufficient data

Extent and occupancy information:

Estimated extent of occurrence (EOO)

392 to 1,800 km²

EOO is 1,061 km² based on a minimum convex polygon around all known subpopulations. It could be as low as 392 km², which is a polygon around recently documented occurrences, or as high as about 1,800 km², if the species proves to be widespread in the Lower Mainland.

Index of area of occupancy (IAO), reported as 2x2 km grid value

24 to 80 km²

Based on all documented subpopulations during the period 1909 to 2023, the IAO is 36 km². The minimum value (24 km²) is based on a calculation using only the recently documented subpopulations. The true value is likely 40 to 80 km², as it is assumed there are more than 10 subpopulations (some undiscovered) but likely fewer than 20.

Is the population “severely fragmented”, that is, is >50% of individuals or >50% of the total area “occupied” (as a proxy for number of individuals) in habitat patches that are both (a) smaller than required to support a viable subpopulation, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

1. Unknown
2. Yes

1. Insufficient data
2. Most subpopulations are separated by > 10 km, and the species’ dispersal ability is < 1 km

Number of “locations” (use plausible range to reflect uncertainty if appropriate)

Likely more than 10 but fewer than 20

There are 6 locations known to be extant and 3 historical locations that might persist. Additional, undocumented subpopulations, and thus locations, likely exist in the Lower Mainland.

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

Likely

Likely, because of observed, inferred, and projected decline in extent and quality of habitat based on habitat loss and fragmentation trends in region.

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

Likely

Likely, because of observed, inferred, and projected decline in extent and quality of habitat based on habitat loss and fragmentation trends in region.

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

Likely

Likely, observed, inferred, and projected decline in number based on decline in extent and quality of habitat based on habitat loss and fragmentation trends in region.

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

Likely

Likely, observed, inferred, and projected decline in number based on habitat loss and fragmentation trends in region.

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

Yes

Yes, observed, inferred, and projected decline in extent and quality of habitat based on habitat loss and fragmentation trends in region.

Are there extreme fluctuations in number of subpopulations?

No

There is no evidence of this, nor is there anything about robber fly biology to suggest this is likely.

Are there extreme fluctuations in number of “locations”?

No

There is no evidence of this, nor is there anything about robber fly biology to suggest this is likely.

Are there extreme fluctuations in extent of occurrence?

No

There is no evidence of this, nor is there anything about robber fly biology to suggest this is likely.

Are there extreme fluctuations in index of area of occupancy?

No

There is no evidence of this, nor is there anything about robber fly biology to suggest this is likely.

Number of mature individuals (by subpopulation):

Subpopulations (each)

Unknown

Insufficient data

Total

Unknown

Insufficient data

Quantitative analysis:

Is the probability of extinction in the wild at least 20% within 20 years [or 5 generations], or 10% within 100 years]

Unknown

Analysis not conducted

Threats:

Was a threats calculator completed for this species?

Yes (see Appendix 2)

Overall assigned threat impact: Medium (2023)

Key threats were identified as

1. Housing and Urban Areas (1.1) – low
2. Commercial and Industrial Areas (1.2) – low
3. Tourism and Recreation Areas (1.3) – low
4. Logging and Wood Harvesting (5.3) – low
5. Recreational Activities (6.1) – low
6. Agricultural and Forestry Effluents (9.3) – low
7. Storms and Flooding (11.4) – low
8. Habitat Shifting and Alteration (11.1) – unknown

What limiting factors are relevant?

• Limited dispersal capability
• Small population and patch size
• Vulnerability to weather patterns

Rescue effect (from outside Canada):

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

Unknown

Known from Washington and Oregon in the United States, but status not ranked. No recent (< 50 years) specimens from Washington, but Oregon specimens have been found repeatedly in recent years.

Is immigration known or possible?

Unlikely

Nearest known U.S. subpopulation is 160 km from Canadian subpopulations. The species is non-migratory and occurs in isolated habitat patches.

Would immigrants be adapted to survive in Canada?

Yes

Likely. No known ecological differences or phenological mismatch.

Is there sufficient habitat for immigrants in Canada?

Yes

Yes, in small, isolated patches

Are conditions deteriorating in Canada?

Yes

Likely decline in habitat extent and quality (see Threats).

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

Unknown

Unknown but likely to some degree (similar threats across the border).

Is the Canadian population considered to be a sink?

No

Is rescue from outside Canada likely, such that it could lead to a change in status?

No

Wildlife species with sensitive occurrence data (general caution for consideration):

Could the release of certain occurrence data result in increased harm to the wildlife species or its habitat?

No

Current status:

COSEWIC status history

Designated Special Concern in May 2024.

Status and reasons for designation:

Status

Special Concern

Alpha-numeric codes

Not applicable

Reason for change in status

Not applicable

Reasons for designation

In Canada, this robber fly’s distribution is limited to openings in early to mid-successional forest in British Columbia’s Lower Mainland. The larval stage is found only in sandy or gravelly soils. There are nine subpopulations documented, three of which are known only from historical records. Additional subpopulations probably exist but the total number is likely fewer than 20. The species’ habitat is at risk from development and degradation from multiple causes.

Applicability of criteria:

A: Decline in total number of mature individuals

Not applicable

Not applicable. Population trends unknown.

B: Small range and decline or fluctuation

Not applicable.

Not applicable. Known EOO (1,061 km²) and IAO (36 km²) are below the thresholds for Endangered, and there is an observed, inferred, and projected decline in quality of habitat. However, the population probably occurs at more than 10 locations. There is insufficient data to determine if it is severely fragmented, and it does not experience extreme fluctuations.

C: Small and declining number of mature individuals

Not applicable.

Not applicable. Number of mature individuals is unknown.

D: Very small or restricted population

Not applicable.

Not applicable. Number of mature individuals is unknown. IAO exceeds 20 km² and number of locations is greater than 5.

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 (2024)

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)^*

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)^**

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

Data Deficient (DD)^***

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.

^* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
^** Formerly described as “Not In Any Category”, or “No Designation Required.”
^*** 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.

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

Current classification:

Class: Insecta

Order: Diptera

Family: Asilidae

Genus: Lasiopogon

Species: Lasiopogon pacificus Cole and Wilcox 1938

Common names:

English:

Pacific Sandpirate (Cannings et al. 2023)

Pacific Lasiopogon (COSEWIC 2018)

Pacific Sand-Robber (Cannings 2018)

West Coast Robber Fly (Hébert pers. comm. 2023)

French: Asile de la côte Ouest (Hébert pers. comm. 2023)

Synonyms and notes:

There are no synonyms or subspecies of Lasiopogon pacificus. It is one of a relatively diverse genus of robber flies, with at least 60 species of Lasiopogon found in North America (Cannings 2002; McKnight and Cannings 2020). Pacific Sandpirate is part of a clade of five closely related species informally called the “aldrichii species group” (Cannings 2002; McKnight and Cannings 2020) that are best distinguished by the morphology of the genitalia, by molecular genetics, and by geographical distribution.

Description of wildlife species

Pacific Sandpirate is difficult to identify for an untrained observer, and even photographs (for example, on iNaturalist) are not always identifiable to species.

Adult Pacific Sandpirates are medium-sized robber flies about 1 cm in length (front cover photograph and Figure 1). As with other robber flies, they have a black piercing proboscis, a sunken gap between the compound eyes on the dorsal side of the head, and a prominent tuft of bristles sticking out between the mouth and the antennae (the mystax or mustache). Lasiopogon can be recognized by the following characteristics: the space between the eyes which diverges laterally above the antennae, a prominent swelling on the face, the abdomen which is elongate and mostly cylindrical, and the external genitalia of the male which are divided into two laterally grasping claspers, in contrast with those of the female, which have an apical crown of short spines and a trough-shaped ventral keel. Technical keys to robber fly genera are available (for example, Wood 1981).

Figure 1. Male Pacific Sandpirate (Lasiopogon pacificus) collected 31 May 2022 in BC: Mission, Steelhead subpopulation. Photo by T.A. McKnight.

Three other Lasiopogon species are found in the lower Fraser River Valley: L. puyallupi, L. cinereus, and L. fumipennis, and at least four others occur in other parts of British Columbia. Pacific Sandpirate can be recognized by this combination of traits: mustache hairs black, three dark stripes running longitudinally down the brown-coloured top of the thorax, haltere knob cream-coloured, dark legs, abdominal segments each dark brown with a narrow apical straight ring of pale grey, external genitalia of the male with the main claspers stocky and wedge-shaped, broadest apically, in contrast with the female’s dark brown ovipositor with the apical ventral plates ferruginous and tapered. Females (Figure 2) are often slightly larger than males, but the sexes do not differ much otherwise except with regard to the genitalia. Technical keys to species have been published (for example, Cannings 2002; McKnight and Cannings 2022).

Little is known about the immature stages (eggs, larvae, and pupae) of this species and microscopic examination is required for identification to the genus level. Descriptions of related species can be found in Melin (1923).

Designatable units

Pacific Sandpirate is being assessed as one designatable unit throughout its Canadian range, which is entirely in the Pacific National Ecological Area (COSEWIC 2020). This is based on a lack of distinctiveness: no subspecies are recognized, and dissections of internal genitalia show no significant differences even between Canadian and Oregon specimens (McKnight pers. obs.). This suggests that dispersal and gene flow between the two extremes of this species’ global range has not been disrupted sufficiently for discernable phenotypic variation to develop. DNA barcodes are available for four specimens of Pacific Sandpirate in the Barcode of Life Data System (Ratnasingham and Hebert 2007), but all are from Oregon and form one barcode index number (BIN). No Canadian specimens have had DNA sequencing for comparison.

Figure 2. Female Pacific Sandpirate (Lasiopogon pacificus) collected 31 May 2022 at BC: Mission, Stave Lake subpopulation. Photo by T.A. McKnight.

Special significance

Robber flies are popular among amateur naturalists, with a growing number of internet-based resources and field guides.

Aboriginal (Indigenous) knowledge

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.

Cultural significance to Indigenous peoples

There is no species-specific ATK in the report. However, Pacific Sandpirate is important to Indigenous Peoples who recognize the interrelationships of all species within the ecosystem.

Distribution

Global range

Pacific Sandpirate occurs along the Pacific coast from southwestern British Columbia to southern Oregon, a range of approximately 62,000 km² (Figure 3). It is restricted to the narrow strip of land at low elevations (usually below 300 m asl) between the coast and the Pacific Coast ranges. Recently documented subpopulations are known in Oregon (McKnight and Cannings 2020) and British Columbia (this report), but no specimens have been documented from Washington state in over 60 years, although this likely stems from lack of surveys.

Figure 3. Global distribution of Pacific Sandpirate (Lasiopogon pacificus) (map by Amit Saini, COSEWIC Secretariat).

Canadian range

The Canadian range of this species is restricted to the lower Fraser River Valley from Vancouver (westernmost) to Chilliwack (easternmost) (Figure 4). There are nine documented subpopulations, six extant and three historical, all verified on the basis of adult specimens or photographs. Given that Pacific Sandpirates do not widely disperse as adults, any site where an adult has been documented is assumed to host a subpopulation. Subpopulations are considered extant if individuals have been documented at a site within the past 20 years and historical if the species has not been documented for more than 20 years but potential habitat still exists. Only a small portion (2% by area) of the global range of Pacific Sandpirate is in Canada. Each occurrence in Canada is considered a geographically distinct subpopulation because they have a separation distance of 1 km (NatureServe 2024), which is slightly more than the farthest known dispersal (that is, 0.7 km, see Movements, Migration, and Dispersal). Therefore, little to no demographic or genetic exchange happens between each generation.

Figure 4. Map of the lower Fraser River Valley in British Columbia showing all extant and historical subpopulations of Pacific Sandpirate (Lasiopogon pacificus), and extent of occurrence (EOO) polygon around known subpopulations (map by Amit Saini, COSEWIC Secretariat).

Pacific Sandpirate museum specimens, survey observations, and photographic records in Canada date from 1909 to 2023, with a minimum of 35 sight and museum records representing nine subpopulations in Canada over this time (Table 1). All of these records have been verified by Rob Cannings or Tristan McKnight, both recognized robber fly experts.

Of the four subpopulations known from historical data (Table 1), only one (“Steelhead”) was verified as extant in recent surveys. However, given that recent sampling could not definitively check all potential habitat patches during favourable weather and seasons, it is possible that the species still persists at the other historical subpopulations. Targeted surveys in 2022 and 2023 produced four previously undocumented subpopulations. A fifth previously undocumented subpopulation was reported to iNaturalist in 2021. This suggests that several additional undocumented subpopulations likely exist.

Targeted search effort includes 109.5 hours of surveying during 107 site visits at 83 sites (62 in the Lower Mainland, 16 on the Sunshine Coast, and 5 on Vancouver Island) over 39 days in May and June in 2022 and 2023 (survey sites shown in Figure 5; see Appendix 1 for more information on search effort). Surveying conditions were not optimal in either year: spring 2022 was relatively cold, wet, and late, and the emergence of many insects seemed delayed by several weeks, and spring 2023 had an unusually dry May which seemed to cause robber flies to emerge earlier at lower abundances than usual (McKnight pers. obs.). While Pacific Sandpirate was still found during the survey, these conditions likely increased the likelihood of false negative results (that is, the species going undetected at sites where it does occur). Additional unsurveyed habitat remains in the three regions surveyed.

Figure 5. Map of southwestern British Columbia showing recent species-specific fieldwork search effort for Pacific Sandpirate (Lasiopogon pacificus) (map by Amit Saini).

Notwithstanding these data gaps and uncertainties, it is notable that Pacific Sandpirate has only been documented in the lower Fraser River Valley, considering that other robber flies and even other Lasiopogon species have been observed at so many localities in southwestern British Columbia (Figure 6). This is strong evidence that the Pacific Sandpirate is limited to the lower Fraser River Valley in Canada.

Figure 6. Map of southwestern British Columbia showing collection localities or observations of general robber flies (Asilidae), non-target Lasiopogon, and Pacific Sandpirate (L. pacificus). Data compiled from specimens databased by the Royal BC Museum (N = 947), select other museums (N = 90), and iNaturalist (N = 1,309), for the area of BC within 51° N and 121.3° W (map by Amit Saini, COSEWIC Secretariat).

Population structure

Population structure within the Pacific Sandpirate has not been studied, but there is no known variation within the species (see Designatable units).

Extent of occurrence and area of occupancy

Current EOO:

The extent of occurrence is between 392 km² and 1,600 km². The EOO calculated using a minimum convex polygon that encompasses all known records from 1909 to 2023 is 1,082 km² (Figure 4). The EOO based on a minimum convex polygon around only recently documented subpopulations is 392 km². If there are additional, undocumented and widespread occurrences in the lower Fraser River Valley, then the EOO could be as high as 1,600 km².

Current IAO:

The known index of area of occupancy (IAO) within Canada is 36 km², calculated using a 2 x 2 km-grid drawn over all known records from 1909 to 2023. The IAO based on only recently documented subpopulations is 24 km², but the same caveats apply as noted for EOO. There are likely undocumented subpopulations which would increase the IAO; however, it is unlikely to exceed 200 km² given the limited potential habitat and apparent rarity of the species. Even in the apparently “suitable” landscape of the lower Fraser River Valley where more intensive surveys have been conducted in recent years, this species has not been found in high densities.

Fluctuations and trends in distribution

There are insufficient data on Pacific Sandpirate in British Columbia to assess fluctuations or trends.

Biology and habitat use

Little is known about the biology of Lasiopogon species and what is summarized below is based on Melin (1923), Lavigne and Holland (1969), Rogers and Lavigne (1972), Haab et al. (2019), and observations made during fieldwork associated with the preparation of this status report (for example, McKnight pers. obs.).

Life cycle and reproduction

Lasiopogon develop through complete metamorphosis, that is, from egg to larva to pupa to adult. Eggs of other robber fly genera have been recorded taking from as little as one day (Machimus) to as long as 56 days (Andrenosoma) to hatch, although the timing for Lasiopogon is unknown (Dennis et al. 2013). Larvae of Lasiopogon are thought to take at least two years to develop based on the size distribution of larvae (Melin 1923); pupae of Lasiopogon have been recorded taking 9 to 17 days to develop under constant temperature (Melin 1923; McKnight pers. obs.), and adults usually live for a few weeks to a month (Haab et al. 2019). Overwintering occurs as larvae; pupae are not found until the spring (Melin 1923).

The adult flight period starts during the transition from late spring to early summer. Canadian records span the period from 7 May to 8 August, with most of them concentrated in late May through mid-June. The precise calendar timing of Lasiopogon adult emergence periods can vary by a few weeks from year to year, likely due to variation in weather (Haab et al. 2019). Lasiopogon generally show a right-skewed emergence pattern (that is, an early surge followed by a gradual decline), with males generally more abundant than females during the earlier half of the season (Haab et al. 2019).

Breeding and ovipositing in Lasiopogon occurs throughout the adult’s lifespan and both sexes are polygamous (Haab et al. 2019). No data on fecundity are available for Lasiopogon, but the size of egg masses laid by other robber flies varies between 1 egg mass in many genera to over 300 in Damalis (Dennis et al. 2023). Dissected female Laphria, Rhadiurgus, Eutolmus, and Dymachus were found to contain 60 to 400 eggs within their bodies (Melin 1923). To oviposit, female Lasiopogon bury their abdomen halfway into sandy ground near the base of plants (Melin 1923; Rogers and Lavigne 1972; Haab et al. 2019).

Survival rates are not known, but the larvae of other robber flies reared in the laboratory have a high mortality rate due to parasitic nematodes, predation by other invertebrates, and environmental stressors such as desiccation (Musso 1981). A mark-resighting study on a different Lasiopogon species found a median adult lifespan of six days, but some individuals survived for several weeks (Haab et al. 2019).

Habitat requirements

Pacific Sandpirate inhabits early- to mid-successional forest in the Coastal Western Hemlock biogeoclimatic zone, usually in hilly dry forest openings at low elevations not far from streams. Most species of Lasiopogon are usually found in relatively open sandy or rocky habitats often near water, although some can be found in forest or heathlands (Cannings 2002). All life stages exist within the same general habitat, but immatures are only found underground while adults live aboveground. Adults tend to perch in exposed open sunny patches on bare sand or low rocks and logs during the day and shelter overnight; in poor weather, they may use perches hidden in low shrubbery (Lavigne and Holland 1969; Lehr 1984). Several species can often be found in the same general habitat at the same time, but differences in microhabitat or seasonal phenology may facilitate niche partitioning and coexistence (McKnight 2017).

Little is known about the specific habitat requirements of Pacific Sandpirate. The original description of the species includes it in a list of taxa that were found “on the dry sands of the sea beach and in open spots in the woods near the ocean” (Cole and Wilcox 1938). By contrast, a recent collection activity in Oregon found specimens perching in hilly forest openings and trails within a kilometre of the ocean beach and nearby streams (McKnight and Cannings 2020; Moon pers. comm. 2022). In Canada, extant subpopulations of Pacific Sandpirate are found in a variety of habitats: trails through second-growth coniferous and mixed forest, rocky streamsides through mixed forest, and sandy riversides surrounded by shrubs and forest. Recent surveys in Washington State have not found Pacific Sandpirate on broadly open sand dunes or rocky beaches of major rivers, lakes, or the ocean, even when related species such as L. puyallupi or L. tumulicola were found there (McKnight, pers. ob.). Pacific Sandpirates have also not been found in unbroken mature forest, which is likely too heavily overgrown, dark, and damp for Lasiopogon.

Pacific Sandpirate occurs in the Coastal Western Hemlock (CWH) biogeoclimatic zone, with most subpopulations occurring in the Dry Maritime (CWHdm) subzone and Eastern Very Dry Maritime (CWHxm1) variant. Occasionally it also occurs in the Very Wet Maritime (CWHvm1) variant (British Columbia Ministry of Forests 2009). Within this ecosystem, the species inhabits forested sites at early- to mid-successional stages. Some periodic disturbance either from natural (for example, blowdown, floods, or erosion) or anthropogenic (for example, tree removal, trail building) causes may help maintain a constellation of open areas with seral communities where subpopulations of Pacific Sandpirate can live. Some of the dominant vegetation observed at sites in Canada with extant subpopulations of Pacific Sandpirate include pioneer or early-succession trees such as alder (Alnus), birch (Betula), or maple (Acer), and only younger individuals of climax species such as hemlock (Tsuga), cedar (Thuja), or Douglas-fir (Pseudotsuga menziesii). Shrubs, ferns, and groundcover such as Rubus and Pteridium were also abundant. Within this broader landscape, the microhabitats where Pacific Sandpirate were found generally have sandy or gravelly soils with intermittent elevated perching sites such as fallen logs (not freshly cut, but also not yet weak from decay) or boulders.

The soil consistency of Lasiopogon larval habitats needs more study but likely contributes to the patchy and limited distribution of these species. The dominant soil types where adults were observed at the six extant subpopulations were as follows: two Recent Alluvium (sand), two Buntzen (sandy loam, moderately well drained), one Isar (sandy loam, rapidly drained), and one Glen Valley (very poorly drained) (Comar et al. 1962; Luttmerding 1981; BC Soils Information Finder Tool 2018). While these represent a range of soil types, a combination of alluvial deposits and glacial till with moderate amounts of gravel seems to be generally common. Soils dominated by silt or clay are likely too fine for most Lasiopogon, and shingle, cobble, or boulder fields are likely too coarse. Although Pacific Sandpirates are sometimes found in microhabitats with abundant boulders, sand is common in those sites. The substrate of the Fraser River changes from a predominantly sand bed to a gravel bed just upriver of the easternmost known subpopulation (Church 2017). This may limit potential habitat for this species beyond this point, although some of these soil types are found as far east as Hope. Some of these soil types are also found along the Sunshine Coast at least as far as Sechelt.

A spatial mapping exercise was conducted to estimate the extent of potential habitat within the known range of the species in the Lower Mainland as well as in neighbouring regions (Wray and Heron 2023). Land was considered suitable habitat if it met these three requirements: 1) any of the three appropriate Coastal Western Hemlock biogeoclimatic subzones or variants, 2) elevation below 300 m asl, and 3) majority deciduous mixed forest of any successional stage. The area of potential habitat for Pacific Sandpirate was estimated at 410.86 km² in the Lower Mainland, 346.79 km² on the Sunshine Coast, and 331.97 km² on southeastern Vancouver Island, giving total potential habitat of 1,089.62 km². Furthermore, the area of land in the Lower Mainland and Sunshine Coast with any of the four soil types documented for this species is estimated at 354.76 km² (BC Soils Information Finder Tool 2018). These calculations likely overestimate suitable habitat as they do not account for poorly understood microhabitat requirements. Nonetheless, they do give an idea of the spatial extent of habitat available for this species in the region.

Movements, migration, and dispersal

The dispersal ability of Pacific Sandpirate has not been studied, but some information can be inferred from research on other species in the genus. Although Lasiopogon are capable of agile flight, most individual flights are quite short (only a few metres) and dispersal between discrete patches of suitable habitat is relatively rare. Lasiopogon tend to stay relatively low to the ground (usually less than 3 m) when flying or resting, so they are unlikely to be picked up and carried long distances by the wind. Environments favoured by most Lasiopogon tend to have shifting fragments of optimal habitat that change over the years as disturbance and succession create openings in or close patches in the forest environment or floods move sandbars along a river. The longest overall dispersal recorded from mark-resighting experiments of hundreds of individuals for two other Lasiopogon species is only 0.7 km, and most marked individuals stayed within only a few dozen metres of their original sighting even after several weeks (Haab et al. 2019; McKnight pers. obs.). Kilometre-scale dispersal, even if rare (less than 1%), likely allows a metapopulation to find new habitat patches and thus avoid local extirpation under natural conditions. There is no migration for this species.

Adult Lasiopogon move between their nighttime roosts (usually perching on twigs and shrubbery on the periphery around a patch) and their exposed daytime perches (on rocks, logs, or bare sand out in the open). Within a day, they move due to stochastic action (chasing a prey or mate, avoiding a predator) or to occupy sunlit patches (Lavigne and Holland 1969; Haab et al. 2019). Despite this frequent motion, individuals often show some site fidelity which can be likened to home range behaviour, such as returning to perches within the same few metres day after day instead of moving all over the microhabitat patch and chasing away other encroaching individuals (Haab et al. 2019). The median home range observed was 20 m² (Haab et al. 2019). Subpopulations can be quite patchy throughout a landscape, sometimes localized to microhabitats only 100 m in diameter and absent from different microhabitats only a few metres away (Haab et al. 2019).

Anthropogenic dispersal is unlikely as the species is not attracted to or associated with humans. Adults are usually quite wary of humans and flee when approached. Larvae could conceivably hitchhike in shipments of sand or topsoil although this has never been observed.

Interspecific interactions

Robber flies such as Pacific Sandpirate occupy an intermediate trophic level in the insect food web. They can provide direct or indirect control for some insects through predation and competition (Musso 1983; Rees and Onsager 1985) but also serve as food for some larger predatory insects or vertebrates.

Most information regarding any Lasiopogon species’ interactions with other species deals with the prey of adults. Robber fly larvae and adults are usually generalist predators of other insects. Prey is grabbed in the adult fly’s bristly legs and the proboscis is inserted into the body. Paralyzing and proteolytic saliva is injected and the tissues are dissolved; the resulting fluid is sucked up by the fly.

Diet:

Only one prey record of Pacific Sandpirate is known (a stonefly), but data compiled about related Lasiopogon species suggest that the adults are generalist predators that feed mainly on small flies, true bugs, and flying aquatic insects. Published prey records (N = 234) compiled from several Lasiopogon species were 63% Diptera (from 28 families, but two thirds from just five families: Chironomidae, Tipulidae, Anthomyiidae, Empididae, and Muscidae), 19% Ephemeroptera, 13% Hemiptera (mainly Cicadellidae and Aphididae), and the remaining 5% a mix of Trichoptera, Coleoptera, Hymenoptera, Isoptera, Lepidoptera, Odonata, Plecoptera, and Acari (Lavigne 2016; Haab et al. 2019; McKnight and Cannings 2020). Lasiopogon prey are broadly diverse when aggregated on the genus level. In addition, studies focused on individual species have shown 8 to 17 families of prey taken over just a few days at a single site (Lavigne and Holland 1969; Rogers and Lavigne 1972). Conspecific cannibalism has been recorded in several species of Lasiopogon but is apparently fairly rare. Cannibalism rates for other robber flies appear to be inversely correlated with prey abundance (O’Neill 1992). Prey of larval Lasiopogon are unknown, but the most common prey for other robber fly larvae are scarab beetle larvae (Wood 1981).

Predators and competitors:

No predators or competitors of Pacific Sandpirate are known, but some can be inferred from related species. Major predators of Lasiopogon include other robber flies (Lehr 1984; Lavigne 2016), spiders (Dennis et al. 2012), and vertebrates such as birds and lizards. Competition and predation by other robber flies might be the greatest day-to-day concern for adult Lasiopogon. Dragonflies and damselflies may be a source of intraguild competition or even predation because they often live in the same habitats, tend to feed on prey similar to those consumed by Lasiopogon (for example, small Diptera; Pritchard 1963; Kaunisto et al. 2020) and are occasionally prey of robber flies or vice versa (Lavigne 1976; Do and Choi 2019). Predators and competitors of larval Lasiopogon are unknown.

Host/parasite/disease interactions:

Little information exists about parasites or diseases of robber flies. Parasitic mites are occasionally observed on adult specimens, and larvae sometimes die due to nematode infection.

Physiological, behavioural, and other adaptations

There are no specific data on physiological adaptations of Pacific Sandpirate but some inferences can be made from related species. Like most Lasiopogon, it is a spring-flying species and probably has a higher tolerance to cool weather than many robber flies that fly in mid-summer. Some species in the genus are found farther north than any other robber flies, as far as the shores of the Arctic Ocean. Southern species from Mexico are only found in mountain habitats (McKnight and Cannings 2020). In some Lasiopogon species, adult activity has been recorded in air temperatures as low as 10 to 15°C (Lehr 1984), but this activity is more common above 20 to 25°C (Lavigne and Holland 1969; Haab et al. 2019). They are more active in the sun than in cloudy conditions (Cannings 1997) and generally not active at all when it is overcast and threatening rain; however, they can resume activity within minutes or hours if sunny conditions return. One study found activity occurred only once light intensity reached a level roughly equivalent to a mostly shady place on a clear sunny day (Haab et al. 2019).

Lasiopogon may be more vulnerable to desiccation than many other robber flies. They are one of the few taxa that have been observed “drinking” (that is, dipping their head to wet sand) instead of only acquiring moisture via drinking their prey (Lavigne and Holland 1969). Many species are found only at sites very close to running water. However, too much water can also be a problem—Lasiopogon are never found near swampy, marshy, or brackish areas. Good drainage is likely important for both larvae and adults. The last instar of robber fly larvae can sometimes survive for months or even years without feeding, as long as the soil does not completely dry out (Melin 1923).

Lasiopogon are likely adapted to cope with minor stochastic disturbances, given that they live on patchy sandy ground prone to erosion near bodies of moving water, in seral vegetation communities, and given their multi-year lifespan with adult emergence focused on the transition from spring to summer. Attempts at captive rearing have to date failed to maintain an entire life cycle, so wild subpopulations are essential for the future of these species.

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 Pacific Sandpirate likely consist of a combination of the factors described below:

Limited dispersal capability:

Pacific Sandpirate is small and does not likely disperse long distances, especially through unsuitable habitats (for example, swampy land, high mountains, asphalt-covered surfaces in cities). Isolation of subpopulations may lead to decreased genetic diversity, greater genetic differences, and inbreeding depression.

Small population and patch size:

Pacific Sandpirate subpopulations are small, isolated, and limited to habitat patches. The average patch size is unknown; however, the size of a patch may limit the subpopulation within a given habitat.

Vulnerability to weather patterns:

Cloudy conditions limit activity and could keep individuals from hunting or breeding frequently, while extremes in frost, temperature, humidity, or precipitation affect survival at all life stages. Extreme weather events in one year could affect the abundance of subsequent generations.

Population sizes and trends

Data sources, methodologies, and uncertainties

Pacific Sandpirate surveys have focused on recording and confirming extant subpopulations and documenting natural history and habitat information. Surveys used wandering transects through suitable habitat (see Appendix 1) and involved collecting specimens as vouchers to document subpopulations. No mark-resighting experiments have been conducted on this species that could estimate subpopulation sizes with statistical rigour.

Abundance

There are insufficient data to estimate the abundance of Pacific Sandpirate in Canada, although the species appears to be relatively rare in its range compared to related robber flies. A total of 35 specimens and observations have been gathered since 1909 (Table 1). In 2022, a total of seven adults were recorded at four subpopulations; for three of these subpopulations, only a single individual was observed during the survey. In 2023, four adults were recorded at two subpopulations.

Fluctuations and trends

There are insufficient data on abundance or distribution of Pacific Sandpirate to assess fluctuations or trends. None of the subpopulations have been repeatedly surveyed in a manner that could detect population changes. Natural population fluctuations in robber flies are poorly understood but likely a result of factors such as parasites, predators, weather, and prey distribution or abundance. Adult Lasiopogon are sensitive to weather, only flying when it is warm and sunny, and null surveys do not necessarily indicate absence. Studies on related Lasiopogon species suggest that peak adult abundance for a subpopulation can vary at least twofold within a few years, but there can also be comparable apparent variation from week to week within a given year (Haab et al. 2020; McKnight pers. obs.).

The known subpopulations of Pacific Sandpirate in Canada are all separated by distances greater than the presumed normal dispersal limit. However, without knowing each subpopulation’s size and without better sampling to assess the actual occupancy of the surrounding matrix, it is impossible to confidently assess the degree of fragmentation.

Rescue effect

Rescue from Pacific Sandpirate subpopulations in the USA is unlikely. The closest known records are in western Washington, about 160 km south of the nearest records in Canada (Figure 3), and much of this gap would be relatively inhospitable: either open Salish Sea or the highly urbanized Seattle metropolitan area. The most recent museum records from Washington are also old (1953), and a handful of informal field surveys throughout that State during the last decade have only found other Lasiopogon species when visiting seemingly suitable habitat (McKnight pers. obs.). While this is likely a result primarily of insufficient sampling, and Pacific Sandpirate probably still exists somewhere in Washington, it suggests that surviving subpopulations are probably small and localized in small patches. Extant subpopulations are known in western Oregon, but these are more than 500 km from the Canadian population. Because Lasiopogon do not migrate and are not known to disperse more than a kilometre (see Movements, Migration, and Dispersal), natural immigration over hundreds of kilometres (or even tens of kilometres in the case of there being closer, undocumented occurrences in Washington State) of fragmented habitat is unlikely.

Threats

Historical, long-term, and continuing habitat trends

The habitat for Pacific Sandpirate is early- to mid-successional forest in the Coastal Western Hemlock biogeoclimatic zone, usually in hilly dry forest openings not far from streams. Over the past century, the lower Fraser River Valley has been subject to waves of extensive resource extraction (for example, logging and sand quarrying), conversion of forest to agriculture, and ever-expanding urban and suburban development, which together have reduced and fragmented potential habitat for Pacific Sandpirate. Efforts to conserve forest stands in protected areas in the Coastal Western Hemlock biogeoclimatic zone may sometimes interrupt some of the natural disturbance processes that once maintained a steady patchwork of early to mid-successional communities suitable for Pacific Sandpirate. Most of the streams in the Fraser River Valley have been altered, including being buried, culverted, or dammed, and subjected to removal or alteration of native riparian vegetation, and inputs of pollution (Department of Fisheries and Oceans Canada 1998). Species in this ecosystem are affected by these changes, and climate change could increase the frequency and intensity of flooding events and droughts. Recent human population growth in the lower Fraser River Valley is also substantial. From 2011 to 2021, the Metro Vancouver Regional District and the Fraser River Regional District had population growth of 14% and 17%, respectively, representing 329,000 and 46,000 people (Statistics Canada 2012; Statistics Canada 2023). This growth is projected to continue into the future. Highway expansion projects and development plans for cities in this region point to further expansion in residential, industrial, and business park capacity, which may encroach on habitat fragments available for Pacific Sandpirate (for example, City of Abbotsford 2004).

Current and projected future threats

Pacific Sandpirate is vulnerable to the cumulative effects of various threats, especially residential and commercial development, logging, recreational activities, pollution, and habitat shifting. The nature, scope, and severity of these threats have been described in Appendix 2, following the IUCN-CMP (International Union for 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 taking into account the separate impacts of all threat categories and can be adjusted by the species experts participating in the threats evaluation.

The overall threat impact for Pacific Sandpirate is Medium, corresponding to an anticipated further decline of between 3% and 30% over the next 10 years. These values are to be interpreted with caution because 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.

Threats specific to Pacific Sandpirate are poorly understood but general threats to Lasiopogon robber flies and their habitat in BC have been assessed based on experience by comparing historical and recent locality data and using long-term observations of local subpopulations. The main categories of potential threats to this species have been identified and are presented in the perceived order of importance in Table 2 below. For more details, refer to the table and Appendix 2.

Residential and commercial development (IUCN 1; low impact)

Housing and urban areas (IUCN 1.1; low impact)

An increase in development to accommodate human population growth may result in unsuitable habitat conditions for Pacific Sandpirate, through clearing or removal of habitat and/or alteration of natural hydrology patterns. This species’ range in British Columbia lies within a densely human-populated region (the Lower Mainland), but many subpopulations are likely already mostly restricted to areas that have some municipal or regional protection from further development. The three historical subpopulations at Bon Accord, Langley, and Vancouver (#1, 2, 4) are in cities that have already gone through extensive urbanization. Therefore, if Pacific Sandpirate still exists there, it is likely restricted to small pockets of habitat within established parks and protected areas. Homeless encampments in municipal parks could damage these pockets of habitat, especially near forest edges and rivers. While the Thornhill subpopulation (#8) falls within a municipal park, the land is actually a mosaic of private and public ownership and depends on a tradition of informal trails, open access, and protection that could be revoked. Furthermore, parts of the city-owned area are designated as “urban reserve” in the City of Maple Ridge’s Official Community Plan, meaning they could be opened for future urban development. Similarly, the City of Abbotsford has outlined a strategy of expanding residential development and the corresponding urban perimeter up hillsides such as Sumas Mountain, in order to preserve established agricultural land in the bottoms (City of Abbotsford 2004). The surrounding habitat for several eastern subpopulations such as Steelhead or Pattison Creek (#3, 6) also faces pressure from the spread of land development into rural properties or suburban subdivisions, which would remove potential habitat for Pacific Sandpirate. The fact that historical subpopulations for which samples were not obtained in recent surveys lie within the most heavily developed portion of this region could point to challenging conditions for survival under more intense development.

Commercial and industrial areas (IUCN 1.2; low impact)

As noted under Housing and Urban Areas, many subpopulations of Pacific Sandpirate are limited to pockets of protected land in an urban or suburban environment. Expansion of commercial and industrial areas could threaten this species if these commercial centres encroach on parkland or other habitat patches. For example, the City of Abbotsford developed an industrial park and an electrical substation at Mount Lehman, which eliminated patches of second-growth and mixed forest (City of Abbotsford 2004).

Tourism and recreation areas (IUCN 1.3; low impact)

As noted under Housing and Urban Areas, many subpopulations of Pacific Sandpirate are found in public parks and may be limited to those areas. Management at increasing human recreational uses (for example, converting natural areas in parks into sports fields, building water parks on rivers or lakes) could degrade the habitat remaining in those patches. Furthermore, increased human visitation may facilitate the spread of invasive plant species which could alter habitat conditions, making the environment unsuitable for Pacific Sandpirate.

Biological resource use (IUCN 5.0; low impact)

Logging and wood harvesting (IUCN 5.3; low impact)

Logging takes place in many of the regions where Pacific Sandpirate occurs in Canada. While the flies do not apparently require mature forests for their own life cycle, they are invariably found in early- to mid-successional forest in the Coastal Western Hemlock biogeoclimatic zone, which points to the need to maintain suitable areas with this habitat. Extant subpopulations at Steelhead and Thornhill (#3, 8) are found in sites that have clearly seen timber harvesting in recent years or are managed as municipal woodlots, indicating that the species can coexist with some levels of tree harvesting. Nevertheless, in some cases, the extent and pace of cutting could exceed the threshold at which a local subpopulation of flies can survive.

Harvesting of trees can result in the removal of fallen logs that adult Pacific Sandpirate use for daytime perches, and cutting of nearby tree cover could remove branches used for nocturnal perches and habitat suitable for potential prey species.

Human intrusions and disturbance (IUCN 6; low impact)

Recreational activities (IUCN 6.1; low impact)

The large and growing human population in the Lower Mainland and increasing recreational use of public lands could threaten subpopulations of Pacific Sandpirate confined to limited habitat patches. As noted under Housing and Urban Areas, many subpopulations of Pacific Sandpirate are found in public parks that see regular human intrusion and disturbance. Forests at the Thornhill, Chilliwack, and Bon Accord subpopulations (#1, 5, 8) are frequented by hikers, mountain bikers, and/or horses. In the Steelhead forest (subpopulation #3), recreational motorized vehicles and heavy logging machinery use the roads and trails. The Stave River subpopulation (#7) is directly adjacent to a picnic area, and the parks in Vancouver or Langley where subpopulations (#2, 4) might be persisting (for example, Pacific Spirit Regional Park or Stanley Park) see heavy pedestrian traffic. Off-leash dogs could impact Pacific Sandpirate habitat through trampling, defecation, and urination. While Lasiopogon is tolerant of some disturbance, increased activity within these parks could compact or erode the underlying soils, trample young successional plants, and degrade the overall habitat. The cumulative impact of visits by many hikers could degrade the habitat. The three historical subpopulations are likely located within the Metro Vancouver Regional District, which has a much higher population than the areas with extant subpopulations in the Fraser Valley Regional District. Correlated differences in regional park visitation rates may partly help explain the rarity of this species, although this is difficult to assess given the vague information on historical localities.

Pollution (IUCN 9; low impact)

Agricultural and forestry effluents (IUCN 9.3; low impact)

Robber fly habitats bordering agricultural lands, managed forests, or recreational trails may be sprayed with insecticides or herbicides, and runoff from these pesticides could affect non-target plants used as habitat by Pacific Sandpirate or their prey. Adult or larval robber flies could be harmed through direct contact, although little is known of their physiological tolerances. If pesticides are applied regularly, then cumulative effects may lead to long-term declines in Pacific Sandpirate and/or their prey. On a microhabitat level, logging can lead to increased watershed stream discharge and altered nutrient inputs, which can increase erosion and sedimentation (Gregory et al. 1987) and thus change the suitability of the surrounding land for larvae.

Climate change and severe weather (IUCN 11; low impact)

Habitat shifting and alteration (IUCN 11.1; unknown impact)

The implications of climate change for Pacific Sandpirate are uncertain. The species lives in an ecological niche that is exposed to climate change impacts (for example, flooding, decoupled phenological cycles) and has specific microhabitat requirements that can be sensitive to perturbation. Its low dispersal ability may limit its capability to rapidly relocate away from sudden impacts. Even slight differences in vegetation successional stages or substrate grain sizes may substantially impact species fitness. Warming temperatures may allow the species to expand its range at the northern limit of its distribution but may also allow more summer-focused intraguild competitors to emerge earlier in the year and put pressure on Pacific Sandpirate subpopulations. Changes in precipitation and stream flow regimes could change the moisture level in substrates in which larvae live, affecting the plant communities that thrive around them and influencing prey availability for larvae and adults. The Fraser River is experiencing earlier peak runoff and decreased late summer minimum flows (British Columbia Ministry of Environment 2016), which could change patterns of sand deposition and moisture. However, it should be noted that suitable microhabitat patches are dynamic and the timing of spring swings stochastically year by year, so Pacific Sandpirate likely has some innate adaptability to a changing environment. Rapid changes in temperature extremes such as a late frost or heat dome could increase mortality of adults or pupae faster than the species can adapt.

Storms and flooding (IUCN 11.4; low impact)

Climate change is predicted to bring intensified storms in many regions, which could lead to more severe flooding and erosion in Pacific Sandpirate habitat and make habitat patches uninhabitable, at least temporarily. Adults can relocate to some degree but it could take subpopulations generations to recover from large-scale larval mortality. The Chilliwack, Pattison Creek, and Stave River subpopulations (#5, 6, 7) are the most vulnerable to floods. Of note, flooding damage due to an atmospheric river event in the Pacific Northwest (November 2021) evidently washed away areas of suitable habitat at the Chilliwack subpopulation site (#5, recorded in June 2021), which was also flooded during 2022 surveys due to a late and intense melt of the snowpack. Increased frequency of storms could result in persistent cloud cover, reducing the overall time adults can spend foraging and mating.

Number of threat locations

The six extant (that is, recently documented) subpopulations constitute the minimum number of locations. The different subpopulations are likely separated by enough distance that they do not share vulnerability to a single threat. Therefore each subpopulation can be considered a separate location. Urban development, logging, quarrying, and recreational activities are usually decided at a municipal level and thus not likely to simultaneously affect multiple subpopulations. Extreme wildfires or flooding would also likely be limited to a particular watershed or forest fragment.

In addition to these six subpopulations, there are three subpopulations that may persist but are known only from historical records. Given that five of the subpopulations have only been discovered since 2021, and potentially suitable habitat in the Lower Mainland has not been surveyed, it is quite likely that additional, undocumented subpopulations exist, but the total number of subpopulations, and thus locations, is probably less than 20.

Protection, status, and recovery activities

Legal protection and status

Federal protection:

Pacific Sandpirate has not previously been assessed by COSEWIC and is not listed under the Species at Risk Act (SARA).

Provincial protection:

In BC, there are several acts that protect or manage areas for species at risk in the province. The main acts with provisions that could be applicable to Pacific Sandpirate are the Protected Areas of British Columbia Act, the Forest and Range Practices Act, and the Oil and Gas Activities Act. However, Pacific Sandpirate is not listed under the latter two acts and thus their provisions do not apply.

The BC Park Act protects invertebrate species at risk (species assigned to the Red or Blue list by the B.C. Conservation Data Centre [BC CDC]) in provincial parks and protected areas. When species at risk and the habitats they require are known to occur within a protected area, provisions for management are incorporated into the park Master Plan (if the park has a written and approved Master Plan). Pacific Sandpirate has been assigned to the Red list by the BC CDC (BC CDC 2024) but is not recorded from any provincial protected areas. However, there may be potential habitat in provincial protected areas of the BC Lower Mainland.

The species could eventually be listed as “identified wildlife” under the Forest and Range Practices Act (Province of British Columbia 2002) and the Oil and Gas Activities Act (Province of British Columbia 2008). The Identified Wildlife Management Strategy (IWMS) is an initiative established in 1999 by the Ministry of Environment in partnership with the Ministry of Forests and Range (in consultation with other stakeholders) (see Province of British Columbia 2002; WLAP 2004). These acts are applicable to provincial Crown forest and grazing land as well as land use regulated under the Oil and Gas Activities Act. Pursuant to this legislation, identified wildlife and their habitat may be managed to address adverse impacts from forestry or range activities, or oil and gas activities within Wildlife Habitat Areas. At present, however, Pacific Sandpirate is not listed as identified wildlife.

International protection:

Pacific Sandpirate has not been listed under any complementary international or global agreements, such as the U.S. Endangered Species Act or the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

Non-legal status and ranks

The conservation status ranks for Pacific Sandpirate (NatureServe 2024):

• Global GNR (Unranked)
• Canada N2 (Imperilled)
• British Columbia Red List, S2 (Imperilled) (BC CDC 2024)

Pacific Sandpirate has not been assessed in the USA or by the IUCN (IUCN 2022).

Land tenure and ownership

Most of the known subpopulations can be found in protected areas owned at the municipal level. This is partly a result of collecting permits that were arranged for the 2022 surveys and partly due to the habitat preferences of this species (low elevation forests with some disturbance).

If the Vancouver, Bon Accord, and Langley subpopulations (#1, 2, 4) are extant, they are likely be restricted to parks that are owned municipally, regionally, or privately (for example, by the University of British Columbia) and have established protections.

The Thornhill, Chilliwack, and Abbotsford subpopulations (#5, 8, 9) are found in forest stands on a mix of municipal and private land which are protected jointly. The Steelhead subpopulation (#3) is in an area with a patchwork of municipal and provincial public land that is managed as a municipal forest. The Pattison Creek subpopulation (#6) is on a provincial road allowance near private land (Gadsden pers. comm. 2022). The Stave River subpopulation (#7) is on land owned by BC Hydro.

Additional undocumented subpopulations will likely be found in the Lower Mainland. Provincial parks and public land provide much nearby early- and mid-successional habitat that should be surveyed, although this land may be at higher elevations and may have microhabitat differing from that preferred by Pacific Sandpirate.

Information sources

References cited

Collections examined

All known physical specimens of Pacific Sandpirate from Canada have been examined and come from the following collections:

• CAS: Department of Entomology, California Academy of Sciences, San Francisco, California, U.S.A
• CNC: Canadian National Collection of Insects, Arachnids and Nematodes, Ottawa, Ontario, Canada
• FISH: Eric M. Fisher private collection, El Dorado Hills, California, USA
• MCZ: Entomology Department, Harvard Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, USA
• RBCM: Royal BC Museum, Victoria, British Columbia, Canada
• UBC: Spencer Entomological Collection, Beaty Biodiversity Museum, University of British Columbia, Vancouver, British Columbia, Canada

All observations of robber flies from British Columbia (more than 2,000) posted to the web platforms iNaturalist.org and bugguide.net were examined to determine if they might be Pacific Sandpirate. One was found.

No specimens of Pacific Sandpirate were found in searches conducted at the following collections which are regionally relevant although relatively small:

• Burke Museum, University of Washington, Seattle, Washington, USA
• Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
• Pacific Forestry Centre arthropod reference collection, Victoria, British Columbia, Canada
• Slater Museum of Natural History, University of Puget Sound, Tacoma, Washington, USA

No Canadian specimens of Pacific Sandpirate were found in the following collections, although they do contain specimens from the USA:

• AMNH: American Museum of Natural History, New York, New York, USA
• EMEC: Essig Museum of Entomology, Department of Entomology, University of California, Berkeley, California, USA
• ESUW: Department of Plant, Soil, and Insect Sciences, University of Wyoming, Laramie, Wyoming, USA
• FMNH: Field Museum of Natural History, Chicago, Illinois, USA
• FSCA: Florida State Collection of Arthropods, Florida Department of Agriculture, Gainsville, Florida, USA
• MSUC: Albert J. Cook Arthropod Research Collection, Michigan State University, East Lansing, Michigan, USA
• OSUC: C.A. Triplehorn Insect Collection, The Ohio State University, Columbus, Ohio, USA
• TAM: Tristan A. McKnight private collection, Tucson, Arizona, USA
• UCRC: Entomology Research Museum, University of California, Riverside, California, USA
• USNM: National Museum of Natural History, Smithsonian Institution, Washington DC, USA
• WSUC: James Entomological Collection, Washington State University, Pullman, Washington, USA

Authorities contacted

• Cannings, Rob. Curator Emeritus of Entomology. Royal BC Museum. Victoria, British Columbia
• Cannings, Syd. Species at Risk Biologist. Canadian Wildlife Service, Environment and Climate Change Canada. Whitehorse, Yukon
• Filion, Alain. Scientific and GIS Project Officer. COSEWIC Science Support, Canadian Wildlife Service, Environment and Climate Change Canada. Gatineau, Quebec
• de Forest, Leah. Species Conservation Specialist. Parks Canada. Halifax, Nova Scotia
• Gagnon, Jean-Marc. Curator of Invertebrates. Canadian Museum of Nature. Ottawa, Ontario
• Génier, François. Entomology Collections Manager. Canadian Museum of Nature. Ottawa, Ontario
• Govindarajulu, Purnima. Unit Head. Species Conservation Unit, Conservation Science Section, Ecosystems Branch, BC Ministry of Environment and Climate Change Strategy. Victoria, British Columbia
• Grant, Paul. Research Scientist. Aquatic Ecosystem and Marine Mammals Section Science Branch, Department of Fisheries and Oceans. Sidney, British Columbia
• Heron, Jennifer. Invertebrate Conservation Specialist. British Columbia Ministry of Environment and Climate Change Strategy. Vancouver, British Columbia
• Ilves, Katriina. Beaty Centre for Species Discovery, Canadian Museum of Nature. Ottawa, Ontario
• Lake, Randal. Head. Regulatory Affairs, Environment and Climate Change Canada. Nanaimo, British Columbia
• May-McNally, Shannan. Acting Senior Science Advisor. Species at Risk and Atlantic Salmon, Department of Fisheries and Oceans. Ottawa, Ontario
• McDonald, Rachel. Senior Environmental Advisor. National Defence. Ottawa, Ontario
• Renton, Robyn. Conservation Data and Information Analyst. B.C. Conservation Data Centre. Victoria, British Columbia
• Sadler, Kella. Head. Species at Risk Recovery, Environment and Climate Change Canada. Nanaimo, British Columbia
• Saini, Amit. Scientific and GIS Project Officer. COSEWIC Science Support, Canadian Wildlife Service, Environment and Climate Change Canada. Gatineau, Quebec
• Shepherd, Pippa. Species Conservation and Management Ecosystem Scientist III. Parks Canada. Vancouver, British Columbia
• Wilson, Gregory A. Aquatic Species at Risk Specialist. Ecosystem Protection and Sustainability Branch, BC Ministry of Environment. Victoria, British Columbia
• Wu, Jenny. Scientific Project Officer ATK. COSEWIC Secretariat. Canadian Wildlife Service, Environment and Climate Change Canada. Gatineau, Quebec

Acknowledgements

Funding for the preparation of this report was provided by Environment and Climate Change Canada.

Thanks to these authorities for providing valuable data and/or advice: Rob Cannings, Jenny Heron, John Reynolds, John Richardson, Julie Wray, Sean Daniels, and Brad Moon shared details about the species on citizen science platforms. Gretchen McKnight and Karl McKnight provided support and assistance during fieldwork surveys.

The following authorities helped arrange collecting permits for fieldwork surveys: Tanya Bettles and Ken Snowden (City of Abbotsford), Tara Friesen and Ryan Mulligan (City of Chilliwack), Julie Kanya (City of Coquitlam), Colin Priddle (City of Maple Ridge), Graham Watson (City of Richmond), Pamela Zevit (City of Surrey), Gord Gadsden and Charlotte Whaley (Fraser Valley Regional District), Ionut Aron (Malcolm Knapp Forest), Janice Jarvis (Metro Vancouver Parks).

Anthea Carmichael (CAS), Claudia Copley (RBCM), Rod Crawford (Burke Museum), John Esme (Pacific Forestry Centre), Whit Farnum (MCZ), Eric Fisher (FISH), Tiia Haapalainen (Simon Fraser University), Karen Needham (UBC), Jim O’Hara (CNC), and Gary Shugart (Slater Museum) facilitated access to insect collections.

Thanks to Joanna James, John Klymko, and Dave McCorquodale for review and administration for the draft status report, Amit Saini and Alain Filion for assistance with mapping and statistics for the species, and COSEWIC’s Arthropods Specialist Subcommittee.

Biographical summary of report writer(s)

Tristan A. McKnight is an entomologist who has caught some types of Lasiopogon for 14 years in a row, has published several academic articles about robber flies, and taught a 2019 workshop on robber fly identification. His Ph.D. from the University of Michigan was focused on the systematics and evolutionary ecology of Lasiopogon robber flies, which led him to find and collect the first specimens of several Lasiopogon species (for example, L. pacificus) to be recorded in many decades. Tristan works as an Assistant Professor of Practice in the Department of Entomology, University of Arizona, and his research focuses on robber flies and other insects.

Appendix 1. Search effort and data gaps for pacific sandpirate.

Prior to this report, Pacific Sandpirate had not been documented in Canada for many decades, so surveys in 2022 and 2023 were focused on locating extant subpopulations and recording habitat information.

Southwestern British Columbia is one of the more thoroughly sampled regions of Canada for Lasiopogon species but most search effort has consisted of general surveys for robber flies rather than targeted searches for Pacific Sandpirate (Cannings pers. comm. 2021). Null search effort prior to 2022 is poorly documented. However, some insight into the effective null search effort can be gleaned by examining where other robber flies have been documented in this region (Figure 6). Uncertainty regarding the presumed habitat for this long-unencountered species (that is, beach sand versus forest openings) may have influenced experts against looking for this species more broadly (Cannings pers. comm. 2021). Elevation is the source of even more uncertainty for this species. While it is mostly known from low elevations (typically below 70 m), an outlier in the Oregon coastal range was recorded at 1,200 m, which suggests the species sometimes occurs in mountains, although it is mostly replaced by other species in those habitats.

In preparation for recent surveys, taxonomic experts were consulted for lists of any known historical specimens of Pacific Sandpirate (Cannings pers. comm. 2021), and several regional museums were revisited to search for potentially overlooked Canadian specimens in recent, undetermined, or teaching collection material (see Collections Examined). Satellite imagery on Google Earth was used to identify parks and other areas with patches of potential forest or sandy patch habitat near historical sites as well as new but potentially suitable sites in the general region.

Potential robber fly habitat was searched by wandering transects from 9 am to 5 pm on warm sunny days. Robber flies were hand-netted, identification was confirmed, and voucher specimens were collected. These methods are considered typical for this taxon (Lavigne and Holland 1969; Baker and Fischer 1975).

Passive traps were not used for recent surveys—partly because this simplified the legal permitting but largely because they are infrequently used for sampling robber flies. While malaise or yellow pan traps can catch the occasional robber fly, this method entails sacrificing a large bycatch (Clement et al. 2018; Wolff et al. 2018).

Sampling was conducted intensively in 2022 and 2023 during May and June each year (Wray and Heron 2023; McKnight pers. obs.). This window was chosen to coincide with most of the capture dates of historical specimen. The earlier dates were prioritized because subpopulations of Lasiopogon generally have the highest abundances near the beginning of the season, while also giving flexibility to address annual variation in seasonal phenology which can shift by 1 to 2 weeks from year to year (see Life cycle and reproduction). Both years of recent sampling fell during periods with suboptimal Lasiopogon collecting conditions. The 2022 spring was relatively cold, wet, and late, and the emergence of many insects seemed delayed by several weeks. Robber flies were found nonetheless. A related species (L. puyallupi) was found on the first day of sampling in the region, and Pacific Sandpirate was found within the first week—but abundances seemed low, which may have affected sampling success. The 2023 spring was abnormal in the other extreme—a relatively dry May presumably affected the main window for pupal development—and robber flies seemed to be emerging earlier and at lower abundances than usual (McKnight pers. obs.).

Because Lasiopogon species can sometimes be identified from field photographs, observations of robber flies posted by the public on the web platforms iNaturalist.org and bugguide.net were also examined. There are about 2,700 robber fly records in British Columbia listed on iNaturalist between 2007 and 2023, of which 41 records are Lasiopogon and 1 record is Pacific Sandpirate (not counting observations that documented voucher specimens from recent surveys). This observation had an obscured locality, but upon request its author shared the precise coordinates to help direct surveys to promising sites (Daniels pers. comm. 2022). Unfortunately, the site was flooded by high spring runoff during the 2022 surveys and had likely been scoured during the historic flooding in November 2021, although some potential habitat remains on the nearby higher slopes.

Recent (since 2020) species-specific search effort within the potential range of Pacific Sandpirate (Lasiopogon pacificus) in Canada. Search areas marked as “Near” are within a 5-km radius of a known (or presumed, if historical) subpopulation collection site.

Appendix 2. Threats calculator assessment for pacific sandpirate.

Threat classification table for Pacific Sandpirate (Lasiopogon pacificus) across its geographic range in Canada based on the IUCN-CMP (International Union for Conservation of Nature – Conservation Measures Partnership) unified threats classification system. For a detailed description of the threat classification system, see Salafsky et al. 2008; Master et al. 2012. For information on how the values are assigned, see Master et al. (2012).

Species or Ecosystem Scientific name:

Lasiopogon pacificus, Pacific Sandpirate

Date:

4/27/2023

Assessor(s):

Jennifer Heron (co-chair and facilitator), John Klymko (co-chair), Tristan McKnight (report writer), Robert Buchkowski (SSC member), Syd Cannings (SSC member and COSEWIC member for ECCC), Lisa Capar (SSC member), Jeremy deWaard (SSC member), Jayme Lewthwaite (SSC member), Dawn Marks (SSC member), Leah Ramsay (SSC member), Dr. John S. Richardson (SSC member), Dr. Brian Starzomski (SSC member), and Pamela Zevit (City of Surrey).

References:

draft status report and draft threats calculator

Assigned Overall threat impact:

C = Medium