The caterpillar is reddish-brown with orange-brown stripes. It has two horns at the head and rows of sharp, black spines. It is not a caterpillar that lends itself to touching or handling. In addition to its foreboding appearance, the caterpillars, as well as the butterflies, are poisonous. The larvae feed on passion flower vines which contain a toxic chemical that stays in the body, rendering it lethal to anything that tries to eat it.
Sometimes, swarms of Gulf Fritillary Butterflies leave Latin America and fly into southern Texas and Florida, but this species is also a native to its U.S. range.