Boisduval's Blue (Plebejus icarioides) is a common butterfly of the American West, with a few different supspecies recognized.
The top picture shows a mating pair, and it highlights white spots with small black dots on the bottom of the wings.
While the basic underwing pattern changes, it represents the best field identification clue for the species. Typically blue butterflies have larger black dots encircled by smaller white borders.
