Mourning Cloak Butterfly, freshly eclosed

Subject: What’s this butterfly species?
Location: Stanford University
May 3, 2016 7:12 pm
Snapped this photo of a newly hatched butterfly today, May 3. This was taken in Palo alto, ca. Any ideas? I didn’t want to disturb it to get its wings to open.
Signature: Audrey

Mourning Cloak Butterfly
Mourning Cloak Butterfly

Dear Audrey,
We opened your email about two hours ago, and we have been mentally writing our response to you while taking advantage of the waning daylight outside to pick peaches to make a cobbler.  This is a Mourning Cloak Butterfly, a species that hibernates in the winter and lays its eggs early in the spring so that caterpillars can take advantage of tender leaves from elms and willows which we verified on BugGuide where it states:  “Larvae eat primarily willow (
Salix spp.) but also other trees and shrubs including Cottonwood (Populus deltoides), Trembling Aspen (P. tremuloides), American Elm (Ulmus americana), Paper Birch (Betula papyrifera), and Hackberry (Celtis occidentalis).”  In our experience in California the caterpillars also feed on Chinese Elm which has tiny leaves.  Mourning Cloak butterflies will even fly about on winter days when it is warm and sunny, and since it has such an extensive range, in cold climates, it is occasionally seen when there is still snow on the ground.  According to BugGuide:  “First-generation adults emerge in early summer, and estivate until fall, when they re-emerge.”  Because it has two adult dormant periods, hibernation in the winter and extivation in the summer when it is dry, the Mourning Cloak is a very long lived butterfly, relatively.  We don’t believe many butterfly live in the imago or adult stage more than a year, meaning the adult Mourning Cloak that emerges from hibernation dies shortly after laying eggs.  Those old Mourning Cloaks generally have rather ragged looking wings.  Adult Mourning Cloaks rarely feed on nectar.  Mourning Cloaks do feed on plant sap which generally runs in the spring, and ripe, rotting and fermenting fruit which is frequently abundant in the summer.  We hope you got a good look at the opened wings of your freshly eclosed individual, which is the proper term for hatching from the chrysalis, leaving behind the exuvia or cast off exoskeleton which is visible in your image.  Mourning Cloaks often rest with spread wings, the dark, velvety surfaces soaking up the warmth.  Your Mourning Cloak is in the family Nymphalidae, the Brush Footed Butterflies.  Butterflies in the family Nymphalidae have vestigial front legs that are useless for walking, so they appear to have only four legs as the brush legs are held close to the body.

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