Immature Stages ofArgynnis mormonia artonis(Lepidoptera: Nymphalidae) Compared toArgynnis mormonia erinnaandArgynnis mormonia washingtoniain the Pacific Northwest, with Evidence for High Elevation-Mediated Melanism

Abstract

Argynnis mormonia artonis from Steens Mountain (2207 m) in southeast Oregon was reared and the immature stages illustrated and compared to those of two other mormonia subspecies resident in the Pacific Northwest, A. m. erinna and A. m. washingtonia. Gravid females oviposited readily in captivity on desiccating Common Dog Violet (Viola riviniana) and Western Bistort (Polygonum bistortoides) leaves and twigs. Larvae were reared on V. riviniana and after overwintering developed from first instar to pupa in 51–59 days at 24–27 °C. Eggs, pupae and early instars (first-early fourth) of A. m. artonis are similar to those of A. m. erinna and A. m. washingtonia, but the fifth and sixth instars differ by being concolorously black instead of gray, brown or black with white markings. Late instars of A. m. erinna from a high elevation site (Mt Howard, northeast Oregon, 2445 m) were similarly dark colored. These and other observations indicate that larval populations of A. mormonia and perhaps other Argynnis spp. are polymorphic with a greater incidence of melanic late instars occurring in high-elevation populations.