The “Columbia 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. Euphilotes columbiae has no published English name; “Columbia Blue” is an interim common name. In Washington this species was long regarded as a subspecies of Euphilotes enoptes (Dotted Blue), but E. columbiae has now been elevated to the full species level. This species represents all Euphilotes from the “dotted blue group” in Washington except for one very localized population of E. enoptes s.s recently discovered by Bob Pyle in western Yakima County. The name “columbiae” was proposed by Mattoni in 1954 but until now was consider conspecific with E. enoptes.

E. columbiae is widespread in Washington east of the Cascades and is one of our two most common Euphilotes species. The range of E. columbiae beyond Washington is still being determined, but at present is known to include all of the Columbia Basin in northern Oregon and eastern Washington, extending a small distance into westernmost central Idaho. E. columbiae is seldom found far from its larval foodplants, the buckwheats Eriogonum compositum (Northern Buckwheat) early in the flight period, then E. elatum (Tall Buckwheat) later in the season. The single- brooded adults have a long flight period from late April to mid August, thanks partially to this ability to exploit two buckwheat species with offset flowering.

E. columbiae adults fly and mate in mid and late spring, laying their eggs singly on or immediately beneath the flowers of the buckwheat host plants. The eggs hatch about six days after oviposition, and the tiny first instar larvae move into the complex buckwheat flowers. The larvae feed only on the flowers and fruits and apparently remain on the flowers during their entire development. When immature fruits (seeds) are available the larvae bore holes into them and hollow out the insides using their long extendable necks; larvae feeding in this manner are not easily removed from the fruits. The larvae will continue to feed on the fruits after the flower petals have senesced, and by the time pupation approaches a significant percentage of the fruits may have been eaten. Coloration of the larvae appears to be closely linked to the color of the food plants; flowers with more pink coloration produce brightly colored larvae, while pale flowers produce pale larvae. The larvae do not construct nests at any stage, instead relying on cauouflage for protection from predators. Development from egg to pupa is accomplished in about 5 to 6 weeks and overwintering occurs as a diapausing pupa, as in all Euphilotes. From our current knowledge it appears that no other Euphilotes feeds on either of the buckwheat species used by E. columbiae.

Adult Euphilotes are categorized into two groups, the battoides (square-spotted) blue group, and the enoptes (dotted) blue group, each including several western species. These two groups are reliably separated by differences in the male genitalia, those of the enoptes group having larger, more elongate valvae than those in the battoides group. Somewhat less reliable differences are found in the orange spot band along the margin of the ventral hindwing; in the enoptes group the orange spots are chevron-shaped and separated; in the battoides group they are fused together into a broad orange band. Additionally the ventral black spots in the battoides group tend to be more squared and blocky, while those in the enoptes group are more rounded or oval, however some individuals have intermediate spots. In a thorough analysis of the Euphilotes group Andrew Warren (2005) determined that in E. columbiae, as compared to E. enoptes, adults “average larger, males are more lustrous blue above, both sexes have more angular, less rounded wings and better developed, more prominent hindwing aurorae on females.” He also found that E. enoptes feeds on Eriogonum nudum, a different host plant. Warren regarded these differences as consistent, significant and worthy of full species status.

Photos by Dave Nunnallee

G’num2007Vol8No3