Tawny Emperor - Asterocampa clyton

Habitat: Hackberry woods, mountain canyons in Southwest, elsewhere dense fiver woods, dry woods, cities.
Nectar: Hackberries, and occasionally at milkweeds and rabbitbush.
Host: Hackberries.
Habits: Young caterpillars feed and rest in large groups; older ones are solitary.

As identified by other sources, this is probably a Tawny Emperor - Asterocampa clyton (see http://www.npwrc.usgs.gov/resource/distr/lepid/bflyusa/tx/39.htm, USGS).

Identifier: Mike Quinn (Invertebrate Biologist, Wildlife Science, Reserch & Diversity of the Texas Parks & Wildlife)

Left: Tawny Emperor on Hackberry. Courtesy of S. Peregrine Johnson Below: Allen from Caterpillars in the Field and Garden.