Baltimore Checkerspot

The Baltimore Checkerspot is a brushfoot butterfly (family Nymphalidae, subfamily Nymphalinae) found in wetland meadows and bogs across the northeastern United States and parts of the Appalachian region, extending into the upper Midwest and southern Canada. Its bold black, orange, and cream checkerboard pattern makes it one of the most visually distinctive checkerspots in North America.

The species has a close ecological relationship with turtlehead, a wetland wildflower that serves as its primary caterpillar host plant, tying its distribution tightly to the wet meadow and marsh habitats where turtlehead grows. Where turtlehead is scarce, the caterpillars sometimes shift to alternate host plants such as certain plantains or other wetland herbs.

The species holds cultural significance as the state insect of Maryland, chosen for the resemblance of its black-and-orange coloring to the colors associated with Lord Baltimore, after whom the state's colonial founder was named.

• Wings are black above, checkered with rows of orange-red and cream-white spots arranged in bands.
• Underside is more boldly patterned, with larger orange and cream patches separated by black lines.
• Body is dark with fine white speckling.
• Rounded wing shape typical of checkerspot butterflies, with a moderate wingspan.
• Lookalikes: the Silvery Checkerspot has a more orange-brown overall tone without the bold black-dominant pattern, and shows silvery crescents on the underside hindwing margin rather than the Baltimore's cream-and-orange checkering.

Found primarily in the northeastern United States and Appalachian region, with populations extending into the upper Midwest, Great Lakes states, and southeastern Canada. It is closely tied to wet meadows, bogs, marshy fields, and stream-side wetlands where turtlehead grows in abundance. Adults fly for a single period in early to mid-summer, generally June and July depending on latitude.

Adults fly with a somewhat slow, fluttering pattern low over wet meadow vegetation and nectar at a variety of wetland and meadow wildflowers including milkweed and viburnum. Caterpillars are gregarious when young, feeding communally in a silk web spun over turtlehead foliage, a behavior that offers some protection from predators through group vigilance. As caterpillars mature they may disperse to feed individually and sometimes move onto alternate host plants. The species plays a role in wetland meadow pollination during its flight period and its distinctive black-and-orange caterpillars are a recognizable component of wet meadow insect communities.

Eggs are laid in large clusters on the underside of turtlehead leaves. Young caterpillars feed gregariously within a communal silk web through summer, then enter a resting stage as partially grown larvae to overwinter, often within a shelter of webbing and leaf litter at the base of the host plant. Feeding resumes the following spring, after which caterpillars disperse before pupating individually in a hanging chrysalis. There is one generation per year (univoltine), with the species overwintering as a partly grown caterpillar.