The Northern Cloudywing is a member of the family Hesperiidae, the large worldwide family of butterflies classified as skippers. In Washington there are 29 species of skippers, most of which are placed in two subfamilies, the Pyrgine or “spreadwing” skippers, and the Hesperine or “grass” skippers. The Northern Cloudywing is one of our 11 species of spreadwing skippers, and is our second largest skipper after Epargyreus clarus (Silver-spotted Skipper).

Thorybes pylades occurs over most of North America but is local and usually uncommon in Cascadia. Adults fly from late April to mid-July in our area, depending on elevation. This species is found in S British Columbia, along the slopes of the Cascades of Washington and N Oregon, in the Puget Prairies of western Washington and in the Ochoco and Siskiyou Mtns of E and S Oregon.

Preferred habitats include upper shrub-steppe east of the Cascade Mtns, and prairie remnants and heaths near the coast. It often occurs near forests or in recovering clearcuts, also in riparian or other open evergreen forests. Good known locations for this species in Washington include Satus Pass in Klickitat Co., scrub-heath habitats in Mason Co., and Swakane Canyon in Chelan Co. Larvae are sometimes found by searching the host plants for tied leaf nests.

Females lay eggs singly on terminal leaves or inert surfaces near host leaves. Eggs hatch after 5-8 days. First and second instars construct simple nests between two terminal leaves, lightly bound with silk. L3 nests are constructed from 3 or 4 larger leaves stitched together with equally spaced silk ties. Larvae feed nocturnally and frass-shooting is employed to propel their feces away. Larval development is fairly rapid with maturity reached in ~25 days. Fully developed larvae feed well initially then slow, becoming dormant in lightly silked, well camouflaged leaf shelters after about 4 weeks. The mature larvae overwinter in this stage; in the spring they pupate within their shelters without further feeding. Within the shelter the pupa is suspended from two silk strands, one attached at the cremaster and the other slung under the mid section of the horizontal pupa, such that the pupa does not touch any solid surface. The adult skipper ecloses 12-14 days after pupation. Protection is based on ventral gland secretions, camouflage, concealment, nocturnal feeding and frass-shooting to confuse predators and parasitoids. Thorybes pylades is single- brooded and has five larval instars, the final instar varying from sandy tan peppered with tiny black and white spots to a rich reddish-brown. The larval head and collar are black with a dense covering of very short hairs (setae).

Both sexes nectar on flowers, including dogbane and vetches. Males visit mud and perch on shrubs near their host plants, flying out to challenge passersby in search of mates. Thorybes pylades uses many legumes as larval hosts including Lathyrus spp. (wild pea), Lotus nevadensis (“Cowpie” Deervetch), L. crassifolius (Big Deervetch), Trifolium spp. (clover), Astragalus spp. (milkvetch) and Vicia spp. (vetch). Thorybes pylades adults can be challenging to find and are fast, powerful fliers, difficult to catch. Adults are distinguished from other skippers by their large size, heavy body, solidly brown wings, and most importantly by two distinct white marks intersecting the leading edge of the forewing, our only skipper bearing such markings.

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