Elm Sawfly and Pupa

Subject: Butterfly?
Location: Lynnwood, WA
July 7, 2014 6:24 pm
Hello,
this “caterpillar” was found outside of my work. I kept it in a jar with dirt and leaves and sticks, within days it made what looks like a cocoon. But it doesn’t look like any cocoon I’ve ever seen.
Signature: Clarissa Fitting

Dear Clarissa,
This is not a caterpillar.  We hope you are not disappointed to learn that this is an Elm Sawfly Larva and not a caterpillar, because it is an easy mistake to make.  We are very excited because though we have numerous images of both the larva and the adult Elm Sawfly, your documentation is the first image we have received of the cocoon and pupa of an Elm Sawfly.  The adult Elm Sawfly looks like a large bee, and Sawflies are classified along with Ants, Bees and Wasps in the order Hymenoptera, but unlike its relatives, the Elm Sawfly does not sting and is perfectly harmless.