Most years mourning cloak butterflies signal spring’s arrival. This year it’s Milbert’s tortoiseshells.
The first one appeared a few days ago, while snow was still the predominant ground cover. The next day there were two. Warm temps and sunshine took a big whack out of the snow piles, just what the Milbs needed.
These ones were born last August and spent the winter sheltered beneath loose bark or in hollow logs. Their body fluids contain alcohols and glycerols — like antifreeze for your car — which keeps them from freezing when temperatures plummet and food isn’t available.
These winter-hardy butterflies lay their eggs on stinging nettles, the exclusive food of their caterpillars. We have a patch of nettles alongside one corner of our deck — I’ll watch for them there in the coming weeks.
Milbert’s tortoiseshell Aglais milberti