About Aglais milberti (Godart, 1819)
Aglais milberti (Godart, 1819), commonly called Milbert's tortoiseshell, has a wingspan ranging from 4.2 to 6.3 cm, with squared-off forewing tips. The upperside of its wings is black, marked with wide orange submarginal bands that fade slightly to yellow close to the inner edge. Both wings have narrow black marginal borders, and blue spots may be present on the hindwing.
Milbert's tortoiseshell ranges across all of Canada and Alaska south of the tundra, the entire western United States, and most of the eastern United States. Within this range, it is commonly found in wet areas, including moist pastures, marshes, most trails, and roadsides.
This species produces two broods between May and October. During this period, adult butterflies mate and lay eggs. Females lay eggs in clusters of up to 900 eggs on the undersides of host plant leaves. Early-instar caterpillars feed together inside a shared web, while later instars feed alone. Milbert's tortoiseshell hibernates in the adult stage, often in small groups. Adult Milbert's tortoiseshell have been documented mating in low-elevation watercourses in arid regions.
