Amazing story

The ground is still snow covered and the twigs still lined with ice, but as ever, there are caterpillars to be found. A few evenings ago, while searching with a spotlight after dark, I found five tiny twig-mimicking geometers resting fully exposed on some understory choke cherry.

All five turned out to be the same species, Campaea perlata, or fringed looper. They are identifiable from other overwintering geometrids by a fringe of tiny fleshy hairs along their abdomen and by an unusual third set of prolegs, which is absent in similar species.

It appears that I found caterpillars of two different instars, or growth stages, suggesting that this species has the flexibility to overwinter at different ages. Also, one of the caterpillars pictured here is acting as a convenient overwintering vessel for another creature all together. Can you find the black spot on the middle caterpillar? It is a hole through which a developing Tachinid fly larva is breathing. The caterpillar is doomed, but perhaps we will get to photograph the rest of the parasitoid fly's development.

Always amazing how many stories there are to tell, and discoveries to be made, about a few simple gray inchworms in the snow.