Mourning cloak butterflies

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Adult mourning cloak in early spring

The mourning cloak (Nymphalis antiopa) is the earliest butterly to appear in late winter or early spring. This picture was taken last April 3 in the Thielke Arboretum in Glen Rock. Last winter was particularly long and hard; most years mounring cloaks appear earlier in spring, sometimes even during temporary winter warm spells. I thought about them on a particularly springlike day last week. A person can always hope and look forward!

Mourning cloaks have an unusual lifecycle: the reason they appear so early in spring is that they overwinter as adults, usually in tree cavities or under loose bark (yet another reason to leave some dead wood standing on trees–look for a forthcoming post on dead trees and detritus). As soon as the weather warms up, they begin to fly, and the males select territories to defend and in which they try to attract females.

Mourning cloaks are said to have the longest lifespan of any butterfly–almost a full year. Soon after they emerge from hibernation in spring, the butterflies mate. The females lay their eggs on a variety of trees–willow, poplar, elm, and hackberry, among others. The eggs hatch in about 10-15 days, and throughout the spring and early summer, the caterpillars go through 4 or 5 instars, all the while voraciously eating the young leaves. Adults commonly enter an inactive phase, called aestivation, during warm weather. In fall, they wake up and begin feeding, primarily on tree sap, to build up fat reserves for hibernation.

Mourning cloak caterpillar

Mourning cloaks are easy to identify, because no other butterfly has the combination of dark wings (variously described as brown, purple, or maroon) with pale yellow borders. They are large–their wingspan may be up to 4 inches across. They occur throughout the northern temperate zones, particularly in Canada, Europe, and the United States, and live primarily in woodland edges. They are easiest to see in early spring when they emerge. The one in the photo at the top of the post was most likely displaying his handsome wings to attract females for mating.

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