The Eastern Tailed Blue is a member of the family Lycaenidae, the large worldwide family of butterflies which includes all blues, coppers, hairstreaks and metalmarks. In Washington there are about 45 species of lycaenids, about 19 of which are blues. We have two species of Cupido, the Eastern Tailed Blue and the Western Tailed Blue.Cupido comyntas is rare in Washington, known only from the far northeast of the state. The flight period is poorly documented, but adults at Spokane have been reported in late July. Pyle (2002) reported an early-April to early-August flight for Cascadia, including Oregon’s Willamette Valley where it is double brooded, while Guppy & Shepard (2001) reported a shorter flight of mid-June to mid-July in British Columbia where it is single brooded (and very sparsely known). Cupido comyntas, while rare in Washington, occurs and is common throughout the eastern half of America and the southeastern part of Canada. The species is lacking in much of the west but occurs in Oregon and California plus our isolated population in NE Washington. This species has a large distribution

break between the Pacific coast and eastern Colorado, causing a suspicion that it may have been human introduced in the west. However, its use of native host plants in the west suggests that our populations are indeed native.

Oviposition was observed in the Willamette Valley of Oregon on May 18. The female flew very low, with inconspicuous short hops of a few inches between plants, carefully probing the terminal leaves of the host plant with her abdomen. A single white egg was placed on the dorsal surface of a leaf near the stem. The female then flew 8-10 feet and began probing additional plants in short hops. She repeated the process three times, ovipositing twice. Many legumes have been reported as host plants elsewhere including members of the genera Lathyrus, Astragalus, Vicia, Lotus, Melilotus, Lupinus and Trifolium. In the Willamette Valley C. comyntas used the native Lotus, but they rejected three species of non-native vetches (Vicia cracca, V. hirsuta, V. sativa) which were abundant at the same locality. Eggs begin hatching when five days old. First brood young larvae feed on the partially opened terminal bundles of host plant leaves, eating halfway through the leaves in small patches from the ventral side. The larvae grew very fast molting to L4, the final instar, only 10 days post egg hatch. Pupation began on day 20, and the second brood adults began eclosing 28 days post egg hatch. Dornfield (1980) reported that the pupae possess stridulating organs between the abdominal segments and can produce sound. First brood larvae at all stages feed by skeletonizing host leaves, and each larva tethers itself to the host plant with a single silk thread. Second brood larvae more likely feed on the fruits (peas) of the host plants. Scott (1986) reported that the overwintering stage is the nearly mature larva and that they sometimes overwinter in host pea pods. Ballmer and Pratt (1991) indicated that this species is commonly attended by the ant Formica pilicornis. Camouflage is likely an important factor in survival as the larvae are small and green and blend well with their green host plants.

While the Western Tailed Blue is much more lightly marked in most of Washington, care should be taken identifying adults from the far northeast of the state. C. amyntula populations there are heavily maculated on the ventral wings and are easily mistaken for C. comyntas; habitat may provide a good clue in this area as C. comyntas prefers drier habitats while C. amyntula prefers wet areas. The male genitalia differ but can be observed only with dissection. C. comyntas tends to have more extensive ventral orange spots and the black ventral maculations tend to be rounder and more strongly outlined with white rings than in C. amyntula. This species needs field study in Washington to determine whether it is double brooded here, and to better define the flight period.

All photos this page by Dave Nunnallee.

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