Common Name: Thoosa Orange-Tip
This is the East slope representative of the Sara Orange-Tip. In our area it is uncommon, found on lava flows and sagebrush-bitterbrush shrub-steppe north of Lake Tahoe. It is a little smaller than A. sara sara and has the black pattern a little heavier. Females may be slightly yellowish.
There is one brood in early spring (March-May at 5000'). The host plants are Rock Cresses (genus Arabis) and Tansy Mustard (Descurainia). Adults visit flowers of the hosts, as well as Fiddleneck, Wild Onion, and other early-spring flowers of the upland East slope.