The two-tailed swallowtail butterfly (Papilio multicaudata) was designated the official state butterfly of Arizona in 2001. A large butterfly (wingspan 3-5 inches), the two-tailed swallowtail is found only west of the Mississippi in North America (in canyonlands, foothills, valleys, woodlands, and gardens from southwestern Canada through the western half of the U.S. and into Mexico).

The adult butterfly (also commonly called two-tailed tiger swallowtail) has yellow to orangish-yellow wings edged thickly with black. Each wing has 4 almost parallel stripes (the innermost stripe is the longest, while the outermost two may simply be bars). The hindmost part of each wing has a curved row of blue patches and below the blue are several bars or spots of orange. Two tails extend from the rear of the hindwing, with the innermost tail considerably shorter.

The caterpillar (larvae) of the two-tailed swallowtail butterly is light green and marked near the head with four yellow dots and two yellowish eyespots with blue centers. The "neck" of the caterpillar is banded with black and yellow, and the body has several rows of tiny blue dots. The caterpillar turns brownish or reddish just prior to pupation. Caterpillars feed on the leaves of a variety of trees and shrubs, adults drink flower nectar.

Source:

Arizona Legislation: House Bill 2247
Two-Tailed Swallowtail: Idaho Museum of Natural History

Links:

State Insects - 50 States List