Pyrgus argina, (Plotz, 1884)

Pavulaan, Harry, Patterson, Ricky & Grishin, Nick V., 2023, Reassessment of Amblyscirtes hegon (Hesperiidae) as a complex of four distinct species revealed by genomic analysis, The Taxonomic Report of the International Lepidoptera Survey 11 (5), pp. 1-39 : 18-19

syn: argina ( Plötz, 1884)

DESCRIPTION AND PHENOTYPIC COMPARISON OF ADULTS

Color names are given per Color GrabTM and ColblindorTM applications used in the analysis for sake of easy reference. Per Scudder (1863, 1889), this species is recognized primarily by the dark brown color of the ventral hindwings, identified as “Buccaneer” (brown) in the present analysis. The color swatches ( Fig. 14) show hegon to have a very slight violet pigment, compared to nemoris , matheri and gelidus . Some individuals vary to gray brown, with a perceived “peppery ” look , making differentiation from nemoris and gelidus problematic. The ventral forewing apex is similarly colored to the hindwing, being slightly darker (“Brown Derby ”). The last area of the forewing that was analyzed was the darkest portion of the base of the forewing (“Bistre” brown). There was no appreciable difference in color here, between the four species.

The dorsal brown ground color (“Bistre”) differs little from either nemoris ( “Mikado ”) or gelidus (“Very Dark Brown”), but is considerably darker than matheri (“Horses Neck”) ( Fig. 14). Scudder (1889) gives detailed description of the dorsal and ventral spot pattern, which are individually variable in extent across all four species in the hegon complex. The colors of the light dorsal spots (“Double Spanish White”) and ventral spots (“Soft Amber”) differ very little from either nemoris , matheri or gelidus ( Fig. 14) and are essentially unreliable for differentiating the species. In hegon the ventral hindwing spot pattern tends to be reduced in extent, frequently being absent altogether. Specimens confirmed as hegon from northern New England, the Canadian Maritimes and southern Appalachian Mountains have a high percentage of individuals with unmarked ventral hindwings. Other features in the descriptions of hegon and samoset ( Scudder, 1863, 1889) similarly apply to nemoris , matheri and gelidus and pose identification challenges to observers.

Scudder (1889) provided measurements of the forewings in millimeters. Males (n=3) ranged 11.6–12.2 mm and averaged 12.2 mm. The present analysis of forewing length measured males (n=17) ranging 10.0-13.0 mm, and averaging 11.6 mm. Scudder measured female (n=3) forewings, ranging 11.5-12.5 mm, and averaging 12.1 mm. The present analysis measured females (n=7) ranging 12.0-13.0 mm, and averaging 12.4 mm. All sexes averaged together ( Fig. 16) shows hegon adults having forewing length ranging 10-13 mm, and averaging 11.9 mm. Wingspan of males was measured at 20-25 mm (n=17), averaging 22.8 mm, and females (n=7) measured at 24- 26 mm, averaging 24.9 mm. All sexes averaged together ( Fig. 16) show hegon adults having a wingspan of 20-26 mm, averaging 23.4 mm; showing hegon to have the largest and smallest individuals of the four species. Specimens from the northeastern portion of the species’ range averaged slightly smaller, whereas specimens from the southern Appalachian Mountains averaged slightly larger. The measurements show that hegon and nemoris have similar forewing length and wingspan, whereas matheri and gelidus were both larger ( Fig. 16). A larger sample would be necessary to better define size differences between the two regions.

Of interest to us was the difference in the angle of the subapical spot row from the leading edge of the forewing ( Fig. 16), showing little difference between hegon and nemoris . Both matheri and gelidus showed the alignment of the apical spots to have a sharper average angle. While the measured angle varied greatly, hegon , nemoris and to a lesser degree, gelidus ranged closer to a 90° angle than matheri , which showed the apical spot row to sit at a sharper angle from the leading edge of the forewing.

Differences in male genitalia between species are slight and difficult to assess due to individual variation. Typically, a combination of two characters would distinguish the species. First is the extent of development of the broad tooth on the inner surface of harpe, best seen in posterior view ( Fig. 17, note green arrow on panel b) and dorsal view ( Fig. 16b, d, f, h). Second is the shape of valva and harpe in lateral view ( Fig. 16). In A. hegon , the tooth is larger and more robust ( Fig. 17d), similar to A. nemoris stat. rest., but different from both of the two new species, in which the tooth is shallower and does not protrude much between the valvae. In A. hegon , the valva tends to broaden somewhat from the base to harpe, with its dorsal and ventral margins at an angle (in lateral view). This broadening is not only due to expansion of the ampulla region on costa, but also because harpe ventral margin is more convex near the base and somewhat expanded ventrad ( Fig. 16g). This valva shape is quite similar in A. gelidus , from which it can be distinguished by a more robust tooth on the inner surface of valva.