Last night I found this really cool caterpillar in the woods:
Cool, right? So I did some research to try to identify it. Nothing. That caterpillar showed up nowhere in online guides to caterpillar identification. ‘Cause it’s not a caterpillar.
It’s a sawfly, specifically the Elm Sawfly. So it’s not a butterfly or a moth, it’s a fly!
Waitaminute – it’s not a fly either.
The Elm Sawfly is in the order hymenoptera, with bees, wasps, and ants. Here’s an adult.
Okay, so sawflies are a kind of wasp (with about 8000 species described). You can tell them from typical wasps because sawflies do not have that tiny wasp waist. Despite appearances, they are completely harmless. Adults have no stingers and they do not feed, so they cannot really bite.
The “saw” part refers to the serrated edge on the female’s ovipositor. With it, she cuts into leaves or stems to lay her eggs. The eggs hatch and develop into the caterpillar-like larvae. They feed on leaves like proper caterpillars, then weave cocoons around themselves to pupate overwinter. When the pupa emerges as an adult the following spring, the cycle has been completed!