There are about twenty species of blues in Washington, including two species and one subspecies of Celastrina.

Celastrina is a genus of small blues in which the males are bright blue dorsally while the females are mostly brown with less blue and have broad black peripheral bands on the dorsal forewings. The Dusky Echo Blue is regarded as a subspecies of the Echo Blue, Celastrina echo echo, although some consider it to be a full species.

Celastrina echo nigrescens flies in northeast Oregon, east of the Cascades in Washington and in the Kootenay Lakes region of British Columbia, however its range has not been clearly differentiated from that of C. e. echo. In areas where the two subspecies fly together, worn adults of C. e. nigrescens may be seen with freshly eclosed C. e. echo indicating partially offset flights. The flight period for C. e. nigrescens is poorly known but extends at least from April 10-May 29 in Washington and there may be a partial second brood. Known habitats include lower mountain canyons, open shrub habitat and mountain corridors such as roads and trails. Celastrina echo nigrescens utilizes some of the same larval host plants used by C. echo echo, although our database is small. In early April C. e. nigrescens eggs can be found on Cornus sericea (Red Osier Dogwood) and Ceanothus velutinus (Mountain Balm or Snowbrush), and Holodiscus discolor (Ocean Spray or Cream Bush) appears to be used as well.

Males often congregate at mud or ashes and mating occurs in the immediate vicinity of host plants. Males can be numerous while females are reclusive and inconspicuous. Females inspect several terminal bud clusters of a host plant before laying a single egg, tucked between the buds as deeply as possible. Eggs hatch in 3- 4 days and larvae grow rapidly, pupating 17-19 days after hatch, the adults eclosing 9 days later. First instar larvae chew round holes through the sides of flower buds and hollow out the insides. Larger larvae feed heavily, eating only buds and stems, refusing leaves and avoiding aphids. Cornus bud clusters with several damaged

buds are a good field sign for locating larvae. Larvae do not build nests and do not leave the host plant until pupation. Rapid larval development to adult in captivity suggests that C. e. nigrescens may be double brooded, but field observations are needed for confirmation. Larvae are solitary but will withstand crowding in captivity. The mature larva is bright green with reddish brown markings, a bold white side stripe,

and bold white markings in chevron patterns on each segment. The pupa is light brown becoming dark later, with numerous bristly blond setae. There are four instars and overwintering occurs as a pupa. Eggs and larvae may be found on terminal clusters of buds of the host plants, usually 3-6 feet above the ground. In one instance eggs of the sunflower aphid (Aphis helianthi) on dogwood stems hatched concurrently with C. e. nigrescens, and an attack by aphids on a first instar larva was observed, an aphid attaching its sucking mouth parts to the larva while others aphids attempted to do so as well. This appears to be the first report of an aphid attacking a butterfly larva.

The adults of C. echo nigrescens are very similar to those of C. echo echo. The Dusky Echo Blue differs in often having more darkly marked ventral wings, but it varies from nearly as pale as C. echo echo to nearly as dark as C. lucia. The most noticed dark markings include a broad dark band around the edge of the ventral hindwing (VHW). Also the VHW of C. echo nigrescens is said to have a “blurry” appearance, with markings less crisply defined than in C. echo echo. In some areas adults of C. echo nigrescens and C. echo echo may be found together. In such areas C. echo echo usually flies a little earlier but with some overlap. The full extent of the range of this subspecies needs study.

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