Thick-Clubbed Sawfly

(Note: All links below are to external websites and leave the UWM website.) Howdy, BugFans, Sawflies appear infrequently in these pages, the most recently a year ago, in the person of the spectacular Elm sawfly. The sawflies that the BugLady… Read more

Elm Sawfly

The BugLady got a few “what’s this dynamite caterpillar?” pictures from a friend toward the end of summer – one of a larva, and one of a pupal case in not-very-good shape. She usually gets “what’s this wasp/fly?” pictures of the equally-distinctive adult in June. Sawflies are small, primitive wasps (ancestral sawflies were around 250 million years ago) that most people have never heard of, and they usually carry out their business below the radar.

Butternut Woolyworm (Family Tenthredinidae)

Sawfly larvae are fussy eaters, with many species tied to just a few host plants, and some larvae are considered pests. Larval defense strategies include communal feeding (potential predators have trouble figuring out where one larva stops and the next one starts) and spitting vile liquids from their mouths.

Sawflies Among Us (Family Tenthredinidae)

Sawflies are often described as “primitive wasps,” and, in fact, an ancient line within the Symphyta seems to be the ancestor group for the non-sawfly Hymenopterans (the ants, bees, and wasps). Sawfly comes from the shape of the female’s ovipositor, which, according to one source, she carries folded up but can flip open like a jackknife, and which she uses to saw open a hole in plant tissue so she can oviposit (she can’t sting, so resembling a wasp is to her advantage).

O Christmans Tree

‘Tis the Season for conifers to come indoors, so here are two beetles and a primitive wasp whose larvae make their living chewing on assorted evergreens.

Slug Sawfly: A Skeletonizer

Sawflies are primitive (non-stinging) members of the wasp family, sometimes called “plant wasps.” Adults of some species look wasp-like; others are described as resembling flies, and their offspring look decidedly like caterpillars. Sawflies in warmer climes may emerge the same summer and produce a second, and even a third generation. Sawflies and moths make up a large percentage of skeletonizers (Japanese beetles and some species of leaf beetles are also guilty).


Sawflies are considered “primitive” wasps. The adults, which eat little or nothing, are typically seen in late spring or early summer. In general, sawflies overwinter as larvae, in cocoons they make on pine needles, under bark, in stems, on twigs or on the ground. They pupate as the weather warms, chew their way out of their pupal case, and emerge in spring to mate and lay eggs. The larvae resemble caterpillars, and eat a wide variety of plants, but most species limit themselves to just a few food sources.