Eastern Comma Butterfly

Today I had an encounter with another overwintering butterfly -- the Eastern Comma (Polygonia comma). After several cool days, this Eastern Comma is taking advantage of today's sunny 58 degree weather and warming itself on my back deck.  Like the Mourning Cloak, this butterfly will hide from the harsh winter elements under tree bark or in various cavities.  At the first hint of spring warmth, it will emerge to bask in the sunshine and lay its first brood.  These butterflies are quite feisty and are known to fly at other butterflies and insects that invade their territory.   Host plants for their caterpillars include nettles, American elm, and hops.

Overwintering Mourning Cloak

I turned over this chunk of wood while hiking recently, not expecting to find much of anything as the cold weather has already set in.  

Instead, I was pleasantly surprised to discover a mourning cloak butterfly (Nymphalis antiopa). 

It's so well camouflaged that the edges of its wings are barely noticeable against the wood.

While most butterflies migrate or overwinter as eggs, larva or pupae, adult mourning cloaks find a spot under tree bark, in a hollow or another suitable crevice such as eaves of a house, where they remain through the winter in a state of diapause.  Like other creatures that overwinter, mourning cloaks are able to keep from freezing by building up glycerol, an "anti-freeze" in their bodies while also lowering their metabolic rate. It's amazing that such a fragile looking creature can withstand the fury of winter.  By overwintering, mourning cloaks gain by being the first butterflies of spring.  They may be seen drinking tree sap.  The females will lay eggs on host trees - birches, poplars and elms.