Boisduval’s blue (Plebejus icarioides) is a butterfly that ranges from British Columbia to Baja and east to the western edge of the Great Plains. It can be found in mountain meadows, forest openings and sagebrush areas, wherever there is a plentiful supply of lupine species.
Also commonly called an icarioides blue, over time this butterfly has been classified in at least four different genera. Aricia is another generic designation that is often seen in the literature.
The upper side of Boisduval’s blue males are lilac-blue with darker borders. Females may be brown or blue with wider dark borders. Both sexes have a white fringe around the wings. On the underside, these butterflies have black or white postmedian spots. The spots on the forewings are black circled in white, while the spots on the hindwings are all white or may be black, again circled in white. The spots on the forewings are larger than those on the hindwings.
Boisduval’s blue butterflies only have one brood a year. The females lay single eggs on various lupine species, the host plants. There are four larval instars (stages). Second stage caterpillars seek shelter in the duff at the base of host plants and enter diapause over the winter. Early the following spring after further larval (caterpillar) development, Boisduval’s blues pupate at the base of the host plants. Adults feed on nectar from buckwheat and a variety of composite flowers. As the year progresses, caterpillars eat first the leaves, then flowers and finally the seeds of the host lupines.
Boisduval’s caterpillars secrete a sugary substance that is eaten by ants. In return the ants “farm” or protect the caterpillars from parasites and predators. There is even some research that suggests Boisduval’s caterpillars may pupate in ant nests.
This Boisduval’s blue was flying in our pastures near Lookout CA (Modoc County).