The Elm Sawfly (Cimbex americana) is quite a large species of sawfly (the largest in North America, in fact), with full-grown larvae ranging from 1.5 – 2″ long. The larvae range in color from white / light gray or light yellow to light green, and have a middorsal (middle top) black stripe that runs the length of their body. There is also a row of black dots on each side of their body (these are the spiracles, a.k.a. breathing tubes), and the larvae often coil up into a circle when not feeding. Preferred host plants of the Elm Sawfly are elm and willow, but maple, cottonwood, poplar and birch are sometimes attacked as well.
Sawfly adults strongly resemble wasps (and sometimes bees). The larvae strongly resemble caterpillars, but they have six or more pairs of prolegs on their abdomen whereas caterpillars have five or fewer.
Additional Information (with photos):
- Elm Sawfly (BioWeb — University of Wisconsin System)
- Elm Sawfly (University of Missouri Extension)
- Elm Sawfly (BugGuide.net)