Ottoe skipper (Hesperia ottoe) COSEWIC assessment and status report: chapter 3

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Name and classification

Hesperia ottoe W.H. Edwards, or the Ottoe Skipper, is a member of the family Hesperiidae, the Skippers, subfamily Hesperiinae, the Branded Skippers, and the order Lepidoptera, the Butterflies and Moths. No subspecies are recognized (Layberry et al. 1998).

Description

Hesperia ottoe has a wingspan between 29 and 35 mm (Layberry et al. 1998). The upper side of the wings of adult males is yellowish orange with a diffuse brownish border on the forewing (Figure 1). There is a dark, elongated mark, called the stigma, on the forewing of the male. The stigma has a black interior felt patch and contains androconial scales (these contain a male sex pheromone). The underside of the wings is pale yellowish orange without the medial spots (macular band) on the hind wing that are often present on Hesperia species.

The upper side of the wings of adult females is dull brown with pale buff markings (Figure 1). There are usually one or two round, translucent, whitish (hyaline) spots on the front wing among the pale buff band of markings. The size of this translucent spot varies from one individual to the next. Females do not have a stigma on the front wing. The underside of the wings is pale orange (like in males) and there are usually no medial spots on the hind wing, although a few females may have a trace of these spots. Excellent illustrations of adults are given in Layberry et al. (1998) (Plate 2, figures 14-15) and in Howe (1975) (Plate 89, figures 7-8). The genitalia are illustrated in McCabe and Post (1977) (figure 57).

Males of H. ottoe may be confused with the Dakota Skipper (Hesperia dacotae Skinner), the Leonard’s Skipper (H. leonardus pawnee Dodge), and the Plains Skipper (Hesperia assiniboia Lyman). Hesperia dacotae is smaller than H. ottoe.  Both sexes of H. l. pawnee and H. dacotae usually have a faint band of spots on the underside, although in some males of H. dacotae this band is nearly absent. Males of H. l. pawnee have yellow interior felt in the stigma, and females have a squarish translucent forewing spot on the upper side.  Hesperia assiniboia is darker above and has a slightly greenish ground colour on the under side. Hesperia l. pawnee and H. assiniboia fly a few weeks later than H. ottoe, usually in August and early September (Layberry et al. 1998).

The eggs (basal diameter 1.31 mm, height 1.0 mm) are hemispherical in shape and have a smooth surface. They are gleaming white when first laid and turn duller white to creamy yellow after two days (Dana 1991). The larva is greenish brown with a dark brown head and black prothorax. Larvae probably attain a length of 20-25 mm when fully grown. No technical descriptions of the immature stages have been published (Layberry et al. 1998).