In identifying a young larval stage of an Elm Sawfly, it is possible to see a slate gray color while the older larval stages consist of a yellowish green color containing a black stripe that runs along the dorsal portion of their body. The larval stage of the Elm Sawfly contain a wart-like skin texture and acquire a segmented body, similar to most caterpillars, while other larval stages contain a slimy skin texture and lack a segmented body which is comparable to most slugs. The size of full grown larvae are about 2-1/4 inches long and are mobile by using three pairs of true legs posterior to their heads and contain false legs that project ventrally from their segments (Borror et al. 1989).


The adult form of the Elm Sawfly have a body color of either reddish-brown to black or all black with some yellow spots on their abdomen, resembling wasp-like colors.  The average size of the adult Elm Sawfly is about 25 millimeters long and they have transparent, grayish wings projecting out from their thorax for flying. Both female and male adults have a black head with antennae projecting between their light-sensitive eyes, known as ocelli. Their legs are larger and more advanced than the legs of their larval stage and the color of their legs vary in color from orange to black (Borror et al. 1989).