The wingspan ranges from 7.9 to 14 cm (3.1 to 5.5 in)with females being the larger sex. Southern individuals are larger than northern ones. Males are yellow with four black "tiger stripes" on each fore wing. The outer edge of the fore wing is black with a row of yellow spots. The veins are marked with black. The postmedian area of the hind wing is black with yellow spots along the margin. The inner margin of the hind wing has small red and blue spots. The ventral fore wing margin has a yellow bar that is broken into spots. This broken bar is present in both sexes, and is used to distinguish P. glaucus from its close relatives. Females are dimorphic. The yellow morph differs from the male in having a blue postmedian area on the dorsal hind wing. In the dark morph, the areas that are normally yellow are replaced with dark gray or black. The bluish postmedian area on the ventral hind wing has one row of orange spots. A shadow of the "tiger stripes" can be seen on the underside of some dark females.
The Eastern Tiger Swallowtail (Papilio glaucus) is a species of swallowtail butterfly native to North America. It is one of the most familiar butterflies in the eastern United States, where it is common in many different habitats. It flies from spring to fall, during which it produces two to three broods. Adults feed on the nectar of many species of flowers, mostly from those of the Apocynaceae, Asteraceae, and Fabaceae families.