Backyards for Butterflies
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Species A. Milberti
..............................BREEDING HELICONIUS (NYMPHALIDAE) IN A TEMPERATE CLIMATE
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Aglais milberti, the fire-rim tortoiseshell or Milbert's tortoiseshell, is considered the only species of the proposed Aglais genus that occurs in North America from southern Alaska east to Newfoundland and West Virginia and south to California, Nevada, and New Mexico. Their range includes all of the western US and the northeastern US, as well as the Canadian provinces south of the tundra.
The Milbert's Tortoiseshell is a member of the Brushfoot (Nymphalidae) family, a large, diverse family of butterflies that are often some shade or orange. The brushfoots derive their name from the reduced forelegs of both males and females. Brush-footed butterflies generally have large, prominent knobs on their antennae.
The wingspan is between 4.2 and 6.3 cm and the forewing's tips are squared off. The upperside is black with wide orange submarginal bands; this orange slightly fades to yellow near the inner edge. Both wings have narrow black marginal borders; the hindwing may have blue spots.
This is a quick species that flits rapidly around woodland roads. When it lands it may open its wings, often on trees or rocks.
Milbert's tortoiseshell's range includes all of Canada and Alaska south of the tundra, all of the western United States and most of the eastern United States. In these areas they commonly occur in wet areas, including moist pastures, marshes, most trails, and roadsides.
There are two broods from May to October. During this time adults mate and lay eggs. The female will lay her eggs in bunches of up to 900 individuals on the underside of the host plant's leaves. Early-instar caterpillars eat together in a web, but later instars feed alone. They hibernate as adults, often in small congregations. Adults have been known to mate in low-elevation watercourses in arid regions.
The eggs of the Milbert's Tortoiseshell are pale green. They are shaped like a barrel with vertical ribs. The mature caterpillar (larva) is black and spiny. It is heavily speckled with white and has a broken yellow lateral line along each side. The body is pale below. The chrysalis of the Milbert's Tortoiseshell is somewhat variable in appearance. It is either gray or pale golden green with dark brown flecks.