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Stink bug called that for good reason

| Sunday, April 5, 2009

On a bitter cold day in February, I was working at my computer. Out of the corner of my eye, I caught a glimpse of something small, clumsily flying across the room. I was absorbed in my work and didn't take the time to investigate, but made a mental note.

The next day, my wife called me to the kitchen. She had an insect trapped under an overturned water glass on the counter. In the circular prison was a 3/4-inch-long, shield-shaped bug. Its back and legs were shades of marbled brown over a lighter background. The edges of the rear sides of the insect were alternating trapezoids of brown and white. It was an oddly attractive little beast. Most likely, that was what flew by me while I was working the day before.

I knew instantly it was a species of stink bug. The shield shape of the body, along with the large triangular plate on the back, are characteristic of this group of insects. However, all the stink bugs I'd seen before didn't match the pattern or color of this one.

After a close inspection and getting the stink bug to pose for a photograph, I sent the creature back outside. To satisfy my curiosity about the species, I took the lazy path and posted an e-mail to a large group of fellow naturalists across Pennsylvania with whom I keep in touch to share interesting discoveries. The response was swift and voluminous

Associates from all over the state responded with a single identification. What I had found was a brown marmorated stink bug ( Halyomorpha halys ). What I learned was an interesting story of accidental introduction of a foreign species and its rapid spread in a new environment.

After checking several information sources, I found that the brown marmorated stink bug was first found in 1998 in Allentown. Ten years later, this little insect has spread to 28 counties of Pennsylvania (at least it has been collected in those counties), as well as north into New York, east to New Jersey and south to Virginia. It has been collected in Allegheny, Beaver, Butler and Cambria counties of Western Pennsylvania and most likely occurs in most other counties south of the glacial boundary and west of the Allegheny Mountains.

Stink bugs are in the order of insects know as true bugs or Hemiptera, with six legs, two pairs of wings and hypodermic-like mouthparts. There are around 10,000 species of true bugs in North America. This species is native to China, Japan, Korea and Taiwan.

The exact time or method of arrival in Pennsylvania is unknown, but given the widespread nature of global trade it's easy to imagine stink bugs in Japan piling into a shipping crate for shelter, then the crate being whisked away to a company in Allentown, and the bug crawling out into a new world.

For brown marmorated stink bugs, that new world is paradise. This nirvana has new juicy plants to feed on and none of those nasty natural predators or disease to level off the population. This lack of predators means that all of the young can live, grow and reproduce without a check on their population. Thus, the stink bugs breed and spread quickly.

Our climate is very much like that of Japan with warm, steamy summers and colder winters. The response of these stink bugs to cold weather is to seek shelter to go dormant and overwinter.

The adults, who emerge in August, live out the late summer and then, when fall rolls around, they seek shelter. Our houses have plenty of nooks and crannies where they can hide and stay relatively warm. If the bugs crawl enough, they get into the 70-degree indoor climate and become more active, doing things like flying across the room while a naturalist works on his computer.

Stink bugs, in general, feed on plants. They use their hypodermic-like mouth parts to pierce the fruits and feed on the juices. A few stink bugs feeding on a plant usually don't do any harm. However, lots and lots of stink bugs can ruin a crop. In its native range, the brown marmorated stink bug feeds on fruit trees including apples, peaches, and citrus fruits. The newly arrived traveler hasn't yet become an agricultural pest in Pennsylvania, but growers are keeping a close watch on their crops.

Closer to home, literally, having stink bugs in your house isn't a problem as long as you don't begin to get rid of them by squashing. They aren't called stink bugs for nothing.

Stink bugs exude a malodorous fluid from openings on the side of their bodies. The stink is a means of defense. If they are disturbed by a natural predator, they let loose the smell in the hope the attacker will stop and leave the bug alone. It's good for the individual and for the species. Many birds that feed on insects have a good memory and are able to recognize insects that proved to be uneatable. So, once a bird tries a stink bug and gets a beak full of stink, they avoid other bugs similarly colored and marked.

Because stink bugs have the fetid fluid in their body, stepping on them squashes the gland and releases the smell even though they are dead. The lesson here is, don't squash the stink bugs.

What to do instead?

The best management of stink bugs in your house is to keep them from getting inside. Even the smallest openings around windows, doors and pipes provide places where the insects can crawl. Sealing these with caulk prevents entry.

After they are inside, it's not a good idea to use "bug sprays." They don't get to the creatures still in the cracks, and they leave a residue that can be ingested by small children or pets. The residue also dries and, ultimately, tiny particles get into the air. That's the air you breathe. Also, don't be tempted to suck them up with a vacuum. There are lots of spinning parts in a vacuum cleaner that will chop the bugs into pieces and, unfortunately, release the stink.

The best thing to do is, using a stiff piece of paper -- an index card works well -- scoop up the stink bugs and drop them into a jar partially filled with water. After you get them all, dump them down the drain. Avoid flushing stink bugs. That method doesn't cause any lingering problems, but it's a lot of water to waste just to get rid of one or two small bugs.

Don't worry about being bitten when the stink bugs are on the paper. Their mouth parts are very small, and our skin is too tough for them to penetrate. Anyway, while they are on the paper, take the time to give them a good look to observe the fascinating structure and detail of these common insects.

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