Saturday, September 12, 2009

Adirondack Sawyers: Our Longhorn Beetle

A couple years ago I went out with a local biologist to listen for whippoorwills as part of a census that was being conducted in the Adirondacks. We were assigned some back roads around Bolton, and we had to drive them after sunset. Several times we would stop, get out of the vehicle, and listen for the tell-tale “whip-poor-will” call.

One of our stops found us surrounded by trees in the middle of nowhere (a real backwoods road). It was dark, and it could’ve been creepy, in that way that only dark, strange woods can be at night. As we stood there listening to the silence, we started to hear a strange sound. It’s hard to describe, but overall it could be likened to a quiet, slow sawing sound – like that of a bowsaw being drawn through wood on short strokes. Fortunately, both of us were prepared, for we both have degrees in forest biology. If we hadn’t, this sound might’ve freaked us out. But thanks to our education and a love of the woods, we were pretty confident that what we heard was the chewing sound of a sawyer beetle.

Sawyer beetles are also known as longhorn beetles, and the most common one in the northeastern United States is the whitespotted sawyer (Monochamus scutellatus). This native beetle, recognized by its very long antennae (longer on males than females) and the white spot “between its shoulder blades” (technically at the top of the elytra, or wing covers), makes its living by chewing the bark on the underside of twigs of the balsam fir, assorted spruces, and white pine. This behavior results in flagging: dead twigs, readily noticeable by their reddish color. To some, this damage is merely cosmetic. In fact, many foresters only consider the insect to be a secondary pest, for it often will turn up in trees that are already dead or dying.

The adult female looks for ideal sites for egg-laying: crevices in the bark of weak or recently killed (or cut) trees. After hatching, the larvae start chewing their way into the tree. The youngest instars hang out beneath the bark, while the older ones make their way into the wood, tunnelling towards the heart of the tree. As pupation approaches, the larva turns a 180 and heads back towards the surface. The opening to the world beyond is blocked up with a plug made of wood chips, behind which the larvae pupates. As an adult it emerges from its woody tomb and goes in search of a mate, the cycle beginning once again.

If you want to avoid sawyer beetles on your property, you need to manage the dead and dying timber. Additionally, if you have cut logs lying around, remove the bark and set them in the sun. This will make them less appealing to females looking for egg-laying sites.

The whitespotted sawyer should not be confused with the Asian longhorned beetle (Anoplophora glabripennis), an invasive that is making its way northward, leaving a trail of dead trees in its wake. So far, this beetle has not gotten into the Adirondacks, but that could be only a matter of time. If you find longhorned beetles around your property, learn to identify them; there are only a handful of species in our area and being able to ID them could help save our forests from unwelcome invaders.

By the way, we never did hear any whippoorwills.

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Ellen Rathbone is by her own admission a "certified nature nut." She began contributing to the Adirondack Almanack while living in Newcomb, when she was an environmental educator for the Adirondack Park Agency's Visitor Interpretive Centers for nearly ten years.

Ellen graduated from SUNY ESF in 1988 with a BS in forestry and biology and has worked as a naturalist in New York, New Jersey, and Vermont.

In 2010 her work took her to Michigan, where she currently resides and serves as Education Director of the Dahlem Conservancy just outside Jackson, Michigan.

She also writes her own blog about her Michigan adventures.



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