Dusky Birch Sawfly

Cutting the lawn last night with Emilie and something caught my eye in one of our Birch Trees.

Emilie ran into the house to get the camera and here is what we saw. You gotta admit they are very unusual in how they gather and hang -

These critters are Dusky Birch Sawfly Caterpillars, which have a shiny black head and yellowish green body. Not to be confused with the Birch Sawfly, which have a dull orange head and pale yellowish green bodies with rows of black spots.

Sawflies in the larval stage look very much like moth caterpillars and belong in the group of insects which includes ants, bees, and wasps. They will appear in clusters on foliage of many species of birch. They may cause severe defoliation. All birch species, and occasionally alder and willow, are susceptible.

These critters, like the Eastern Tent Caterpillar, just don't do too well under the weight of a size 9.5 Timberland work boot...

See my Friday, May 18, 2007 post titled Eastern Tent Caterpillar.