Sawfly Near ID

by Carl Strang

In the 1980’s I was inventorying the leaf-eating insects of two forested study areas, at Maple Grove and Meacham Grove Forest Preserves. I was able to identify most of the insects I encountered, but one of the common ones eluded me. It was a sawfly caterpillar that ate the flowers, berries and, at need, leaves of Solomon’s plume (Smilacina racemosa).

This is the sawfly caterpillar in question. Note the head and leg color; these turn out to be important.

Sawflies are herbivorous members of order Hymenoptera (bees, wasps, ants, etc.). One seldom encounters the adults, and the more conspicuous larvae are wretchedly difficult to identify. I tried rearing them, but they overwinter in soil and successful maturation in captive conditions is rare.

Last week on a whim I did a search on “sawfly Smilacina racemosa” and turned up something in Google Books [Smith, David R. 1969. Nearctic sawflies I. Blennocampinae: adults and larvae (Hymenoptera: Tenthredinidae). Tech. Bull. No. 1397, Agricultural Research Service, U.S. Dept. Agriculture]. If I were an entomologist I probably would have found this back in the 80’s, but thanks to the Internet even an amateur can find such references now.

It was an embarrassment of riches, of sorts. It turns out that there are 5 species of sawflies in the genus Phymatocera that are associated with this plant, and all occur in Illinois. Adults can be identified to species, but the best one can do with larvae is narrow them down to 2 or 3 of the species. There is a larva “species 1,” with black heads and legs that contrast in color with the body; three of the 5 sawflies in question are thought to belong to this type. As you can see in the above photo, the larvae I find have brown heads, and legs the same color as the body, and so fall into the “species 2” larval category. So, it would appear that my bug is either Phymatocera offensa or P. similata. The first of those two has in fact been reared on Solomon’s plume in Illinois, while adults of the other have been caught in sweep samples taken from the plant. Makes me think I should try rearing them again, if I can find the time…


1 Comment

  1. December 26, 2012 at 7:25 am

    […] that I was unable to identify two of its members. Later I found a resource that allowed me to narrow down one of the mystery insects, a sawfly, to genus Phymatocera, either P. offensa or P. […]

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