Question Mark Caterpillar

The question mark caterpillar is the larval stage of a butterfly named for a small silvery mark shaped like a question mark on the underside of its hindwing. The species is common across much of eastern North America and is notable among anglewing butterflies for its variable and sometimes strikingly colored larvae.

The caterpillar feeds on the foliage of several common trees and weedy plants, and its populations can build up noticeably on host trees like American elm and hackberry in suburban and woodland settings.

• Body color is variable, ranging from black to reddish-brown to nearly white, often with fine yellow or orange lines
• Covered in rows of branched spines (scoli) along the back and sides, which can be black, orange, or a mix
• Head bears a pair of short, branched spines as well
• Body is cylindrical and moderately robust
• The high variability in color makes individual identification tricky, but the branched spines and host plant association help confirm it
• Similar to other anglewing (Polygonia) caterpillars such as the eastern comma, which is very close in appearance

This species is found throughout the eastern and central United States and southeastern Canada, in woodland edges, parks, and suburban areas with suitable host trees. Caterpillars appear from spring through fall wherever elm, hackberry, or nettle plants are present, often on isolated host trees in otherwise open habitat.

The caterpillar feeds on the leaves of elm, hackberry, nettle, and false nettle, sometimes resting in a loosely rolled leaf during the day. Its spiny body offers some physical deterrence to predators, while its variable coloration may help it blend with different backgrounds or bark. Adults of this species are known for overwintering as adults and being among the first butterflies seen in early spring, making the caterpillar stage an important link in the species' extended activity period.

Females lay eggs singly or in small stacked columns on host leaves. The larva develops through five instars over a few weeks, showing considerable variation in color and pattern between individuals. The mature caterpillar forms an angular, mottled brown or tan chrysalis suspended from a leaf or twig. The species produces two or more generations per year across its range, with the final generation's adults overwintering in sheltered locations such as bark crevices or leaf litter rather than the larvae themselves.