Common Names: Eastern tiger swallowtail
The wingspan ranges from 7.9 to 14 cm with females being the larger sex. Males are yellow with four black 'tiger stripes' on each forewing. The outer edge of the forewing is black with a row of yellow spots. The veins are marked with black. The postmedian area of the hindwing is black with yellow spots along the margin. The inner margin of the hindwing has small red and blue spots. The ventral forewing 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 hindwing. In the dark morph, the areas that are normally yellow are replaced with dark gray or black. The bluish postmedian area on the ventral hindwing has one row of orange spots. A shadow of the 'tiger stripes' can be seen on the underside of some dark females.
Young caterpillars are brown and white; older ones are green with two black, yellow, and blue eyespots on the thorax. The caterpillar will turn brown prior to pupating. It will reach a length of 5.5 cm. The chrysalis varies from a whitish color to dark brown.
P. glaucus can be found almost anywhere deciduous forests occur. Common habitats include woodlands, fields, rivers, creeks, roadsides, and gardens. It will stray into urban parks and city yards. Adults are seen from spring to fall.