What Is all the Stink About?
Dear Dr. Tim,
A brown-colored, disgusting looking bug appeared out of nowhere in my home. It landed on a magazine I was reading. I don’t care much for bugs – most of them creep me out – so, I sent my husband to throw it outside. That was a mistake. Wow did that thing ever stink. Whatever the stink was, it got on his hands and also on the magazine. I had to throw both out. My house reeked for two days and my husband for four. What was that bug and how can I not experience it again?
Yellow arrows point to distinguishing characteristics of the brown marmorated stink bug. Photo Credit:John Obermeyer.
You have just experienced your first run-in with the notorious, brown marmorated stink bug. I don’t even have to see the bug to identify it. You have given me all the clues that I need: (1) it’s inside your home, (2) it’s brown, and (3) it’s stinky.
If it is any consolation, you are not alone. By now many Midwesterners (and certainly most who live in the eastern states) have all experienced an encounter or two with a brown marmorated stink bug – and have lived to tell about it.
But before I explain where the bug came from, why it is in your home, and how to keep it out, I need to tell you that it is time to let your husband back in. It is probably cold out in the garage and beside that, it is not his fault that the bug appeared in your home or that it stank the place up.
Several insects have a habit of entering homes and other buildings to seek shelter for the winter. As a group, we refer to these as “occasional invaders.” Spiders, crickets, some beetles (such as Asian lady beetles), cluster flies, and even stink bugs like the one you found, all enter buildings in the fall. They shelter there for the winter and then emerge during the spring.
Although occasional invaders are serious nuisances, they do not bite people or damage the home structure or its contents. Furthermore, by definition occasional invaders do not eat or reproduce during the winter. They just hang out until the temperatures begin to warm up, then they become active and search for a way back outside.
The brown marmorated stink bug is an invasive pest from China, Japan, Korea, and Taiwan that was accidently introduced into eastern Pennsylvania sometime before 1998. It has since spread across the United States, mostly by hitch-hiking in vehicles and on transported materials.
Brown marmorated stink bugs are about 1/2 to 3/4-inch long. The word “marmorated” means to have a marbled or streaked appearance, thus brown marmorated stink bugs are mottled brown, a characteristic that separates them from other brown insects that may occur inside homes, such as brown-banded cockroaches and leaf-footed bugs.
Brown marmorated stink bugs are shield-shaped, like a five-pointed pentagon, which is typical of the stink bug family (Pentatomidae). Other stink bugs also may be brown, but brown marmorated stink bugs can be specifically identified by their comparatively rounded shoulders and by the alternating dark and light bands on both their antennae and the exposed lateral margins of their abdomen. And while many stink bugs emit a stinky odor, brown marmorated stink bugs are especially adept. They also are much more likely to be found in homes or buildings.
I concede that it is nearly impossible to convince you (or other homeowners) who have had a stink bug infestation that stink bugs are simply a nuisance, occasional invader pest. I admit that. I recognize that they are a serious and aggravating home-invading pest, but they do not bite, spread disease, or physically damage the structure of the house. That is the definition of occasional invader. That is all I am saying.
The stink bug’s defensive mechanism is what you and others will remember long after the bug is removed. The compounds in their odor have been isolated and characterized. They are called aldehydes, specifically trans-2-decenal and trans-2-octenal compounds. People describe the pungent smell as either “putrid” or like coriander. I prefer putrid. I really don’t know what the herb coriander is, for sure, but if it tastes like what stink bugs smell like, I want no part of it.
A brown marmorated stink bug has a unique ability to store these chemicals as a very concentrated, extremely smelly liquid, which it can emit (as needed) through holes in the sides of its abdomen. It is a defensive mechanism – meant to protect it from being eaten by birds, lizards, or other animals.
The magic potion not only reeks to high heaven, it also tastes bad and has even been found to be toxic in some cases. However, the bug does it, I can say that it works like a charm, because nothing I know has ever made a habit of eating them. Even moderately, dim-witted house cats and dogs leave them alone for the most part.
By the way, every time I mention that even pets won’t eat stink bugs, I receive one or two notes from proud cat or dog lovers who brag about how their “special” cat or “unusually brave” dog chases them around and does, in fact, eat them. That is why I qualified my description of such pets as “moderately dim-witted.” That should cut down on the number of pretentious letters I receive, citing exceptional pets.
One entomologist even found that their smell is so bad that stink bugs cannot even stand to be around themselves. Case in point: He found that if he contained a disturbed stink bug in a stoppered vial or kept it in a chamber without proper ventilation, the noxious chemicals it emitted actually penetrated its own respiratory system to the point of asphyxiation. Talk about not standing one’s own stink.
The bugs have become so good at releasing this nasty smell that they do it even when they are hardly bothered – let alone threatened. Simply handling the bug, even while carefully attempting to move it, let alone injuring it, can trigger the release of the odor.
I compare stink bugs to another animal that everyone is very familiar with: skunks. Both manufacture their foul defensive odor via a pair of scent glands located in the abdomen. The scented chemicals are then stored in an internal reservoir located next to the glands until the animal becomes disturbed or threatened.
If you keep skunks in mind when deciding how to get stink bugs out of your home, you may think twice about how to do it. Removal techniques such as coaxing, prodding, shoving, pushing, or ushering by hand, usually do not end well. Crushing them or sending your husband after them with a fly swatter is never a good idea.
Brown marmorated stink bugs are set to begin emerging from their overwintering hiding places – often in our homes – within the next few weeks. Just like when they came inside during the fall, they are mostly noticed during the spring when they attempt to leave. The bug is a relatively large and clumsy flyer, so they often bump around inside the home and even into people when they become active.
Remember that right now, the bugs are simply searching for a way out of the house so that they can go about their summertime, destructive behaviors out-of-doors. Ever so gently assisting them out by using a broom and dustpan is the most effective removal technique. A vacuum cleaner will suck them up, but remember that a “sucked up” bug will always release its disagreeable odor inside the vacuum. You will find that the broom, dust pan and the vacuum will stink and then have to be stored out in the garage where you keep your husband. The garage seems to be filling up fast.
Brown marmorated stink bugs are serious pests on fruits, vegetables, many trees and flowers, and several agronomic crops. As such, many people want to kill them rather than release them outside. This can most effectively be done by carefully dumping or flicking them into a container filled with soapy water. Once in the solution they drown and their stink is significantly masked or reduced. You can keep such a solution on-hand and reuse it at a moment’s notice. Even husbands can be trained in this technique.
I hope this helps you recognize and understand a bit more about why you see brown marmorated stink bugs in your house and how you can deal with them there.