Saturday, January 16, 2010

Adventures in Identifying Insects: Stink Bugs

I’ve become quite fond of photographing insects. This could be because they are so prevalent (when it’s not winter), or it could be because they are so diverse. As a child I disliked anything with more than four legs – “bugs” just creeped me out. Entomology was a required course in college, with its requisite insect collection, but it wasn’t until I started photographing insects in my latter years that their beauty began to intrigue me.

And once one has a collection of insect pictures, one’s curiosity begins to take over. Just what kind of insect is it? Is it a pearl crescent or a northern crescent? A native sawyer beetle, or the Asian longhorn? A plant hopper, leaf hopper or tree hopper?

I’ve been going through some of my insect photos lately and trying to figure out who’s who. Some have been fairly easy to identify, while others have left me confounded. Take the insect in the photo above. My first thought was “shield bug.”

Shield bugs are in the insect order Hemiptera, which are the true bugs. True bugs? Indeed. Contrary to popular opinion, not all insects are bugs. True bugs (and there are about 80,000 species worldwide) are defined by their sucking mouthparts. Think aphids. Cicadas, water boatmen, and water striders are also among the Hemipterans.

Shield bugs are alternatively known as stink bugs, thanks to thoracic glands that produce a rather foul-smelling liquid. When the insects feel threatened (attacked by a predator, picked up by a curious human), they release this fluid and a stench fills the air, usually resulting in the insect’s release.

Not finding a positive ID in my insect field guide, I sent my photo off to www.BugGuide.net, where the friendly insect folks informed me that it is a shield-backed bug (Homaemus sp.), which is often classified with the stink bugs. According to one of the responding entomologists, the only Homaemus we have in New York is Homaemus aeneifrons, so I now had a place to start my natural history investigation.

The problem with insect ID is that there are so many species. As in millions and millions worldwide. And chances are a good chunk of the world’s insects have yet to be discovered. To make things worse, identification doesn’t necessarily mean that much is known about a particular insect. It has been classified and labeled, but that may be it. And so it seems with my shield-backed bug.

A couple hours skulking around various internet entomology sites turned up precisely two pages with anything remotely related to the natural history of this insect. On the first, it was listed as one of several insects to feed on goldenrods. On the second, I discovered that its habitat includes weeds, sedges, swampy meadows and dry places; it is believed to over-winter as an adult; it is presumed to have only one brood per year in the northern part of its range. And that’s it.

So I find myself left wondering if my shield-backed bug, which is classified with stink bugs, has the stink gland that its relations has. Since we are now in the bowels of winter, I have no way to verify this (my photo, sadly, does not have scratch and sniff capability). Somehow, I find my curiosity unfulfilled.

Still, the good naturalist doesn’t let this get her down. Should she not get distracted by other interesting finds, next summer she’ll hunt down another Homaemus and give it a poke and a sniff. She might take note of which plants she finds it on, whether it was feeding there or just resting, and whether others are near by. There’s always room for scientific investigations when it comes to insects, for entomology is a field that still has plenty of unknowns.

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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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