The Silver-spotted Skipper is a member of the family Hesperiidae, the skippers. All North American skippers can be recognized by their recurved antennal clubs. Washington’s skippers currently fit into three subfamilies, the Pyrgine (spreadwing) skippers, the Hesperine (grass or monocot) skippers, and a third subfamily, the Heteropterinae, which in this area includes the Arctic Skipper. In Washington State we have 29 species of skippers, 11 of which are Pyrgine (spreadwing) skippers, including Epargyreus clarus.

The Silver-spotted Skipper is widespread, occurring throughout most of the lower 48 states as well as parts of southern Canada and across northern Mexico. In Washington State, Epargyreus clarus is found in two non-contiguous areas. One area includes most of the lower elevation regions of Washington west of the Cascades, and the other encompasses the southern Columbia basin through the Blue Mountains, connecting with adjacent Idaho. These disjunct populations represent two different subspecies. E. clarus is absent from most of our mountainous areas.

Epargyreus clarus is single-brooded in Washington, overwintering as a pupa, although in captivity it may eclose to a second adult generation which is not normally observed in the wild. Epargyreus pupae eclose in the spring. In Washington the recorded flight period extends from early May through July. After mating the female lays its eggs singly on a small terminal legume leaf, often the topmost leaf on the plant, and typically places only one egg per plant. The egg is larger than other skipper eggs which might be found on the same host plant.

Epargyreus uses legumes as its larval hosts, apparently using only Lotus crassifolius (Big Deervetch) west of the Cas- cades, but Glycyrrhiza (Wild Licorice) or certain species of Locust on the east side. Lotus crassifolius is also used by another skipper, Erynnis persius, with which the larvae can be confused in the earliest stages of development.

On hatching, the early instar larva cuts and folds over a small patch of leaf, silking it in place as a shelter. Feeding on the lush Lotus foliage the larva grows fairly fast and to a large size, becoming one of the most attractive caterpillars of all our State’s butterfly species. Following the earliest instars the larva ties multiple leaves together with silk for its ever enlarging nests. The final instar larva, which reaches the impressive size of 35 mm, is beautifully patterned with a bright yellow body and reddish collar and has a large, glossy black head capsule punctuated with bright orange false-eye spots. In some areas such as the Tahuya Peninsula, E. clarus can be locally common and can be fairly easy to find in its egg and larval stages on the Lotus host plants. At maturity the large larva continues feeding lightly for a considerable time without growing further, then finally pupates to its hibernation stage to repeat the life cycle the following spring.

The pretty Lotus crassifolius host plant also hosts at least three other butterfly species including Callophrys perplexa (Bramble Hairstreak), Strymon melinus (Gray Hairstreak) and Glaucopsyche lygdamus (Silvery Blue).

Epargyreus clarus is our largest skipper species, and is a powerful, darting flier. Adults often stop to nectar, and sometimes may be approached for photography. Owing to its large size together with the presence of a large, dramatic silver spot on the ventral hindwing, the identification of this species is unmistakable in Washington.

G’num2015Vol16No1