The male tiger swallowtail is yellow with black stripes. The female has two forms: one like the male and another that is all black. Both female forms show iridescent blue on the upperside of the hindwings. The underside of the forewing has a row of yellow spots, while the underside of the hindwing has an orange spot. The hindwing also has a projection from the rear edge. The tiger swallowtail has a wingspan of three and ﬁve-eighths to six and one-half inches. Its caterpillar is dark green with two large eyespots behind the head. Early stages of the caterpillar are colored like bird droppings.
The tiger swallowtail may be found statewide in Illinois. Its larva eats the leaves of cherry, birch, tulip poplar and other trees and shrubs. The adult eats ﬂower nectar. The caterpillar has yellow or red structures that can be extended from behind the head when it is threatened.