The brown marmorated stink bug is not native to Maine, but has been carving out a niche of invading human dwellings. Fortunately, it won’t cause any harm in (or to) your home. Matt Rourke/Associated Press

Some of my favorite questions are about the common wildlife that is often overlooked because of its abundance or regularity. Learning about a certain bug that you find in your house or what those trees are that you walk by every day can help grow an appreciation for Maine’s overall biodiversity, and that often starts by learning a species’ name.

Tony McDonald’s question, “(Who are) the ‘stink bugs’ that look a bit menacing, with long legs and an armored body?” is one that I really want to buzz about this week.

Let’s start with the idea of a stink bug. Tony, from South Freeport, opened his inquiry by identifying them the same way most people do: “we are infested … by what we call stink bugs, only because they stink when they are squished.” There are a few insects that do this, and it’s generally because they are deterring predators. Who wants to eat a bad-smelling bug? The odorous chemical that is secreted is typically a type of aldehyde (think of formaldehyde as a common stinky compound) and one you might be familiar with. To my nose, it reminds me of sour apple candies, but you’d recognize aldehydes as also being in cilantro. Kinda funny that the food we garnish our tacos with has the same compounds that we find repulsive coming out of a tiny insect.

So who are they? There are two very common insects that you’re likely to encounter, especially in your house, that are often colloquially called stink bugs. The first, which I tend to see more, is the Western conifer seed bug (Leptoglossus occidentalis). This seed bug is the larger of the two we’ll discuss, and has a longer body, plus distinctly leaf-shaped hind legs. The species is native to North America, but as the name implies it was historically restricted to an area west of the Rockies. It is assumed that this bug spread across the country with the help of interstate trade of goods.

The second species, a “true” stink bug, is the brown marmorated stink bug (Halyomorpha halys). This slightly smaller, shield-shaped insect has only been on this continent since 1998, an accidental introduction from East Asia, which presumably hitched a ride on shipping containers.

It is interesting that both of these smelly insects are not native to Maine but seem to be finding this niche of invading human dwellings. While they can have an impact on some agriculture, they fortunately won’t cause any harm in (or to) your home. These are just some of the frequent reminders that our ecosystems are changing, especially in our ever-globalized world. Hopefully you’ll recognize one of these “stink bugs” next time you see one, and not be too put off next time you garnish with cilantro.



One of the most fun parts about studying nature is that pretty much any topic can spawn a never-ending line of questions. Our recent coverage of squirrels and acorns is one that keeps on running. We haven’t gone full “which came first, the squirrel or the acorn?” yet, but a fun question to ponder came in from Pam Blake of Freeport, asking how squirrels know what is safe to eat.

Pam was specifically asking about mushrooms. We’ll get to that soon but first, let’s start with acorns because, well, squirrels are pretty nuts about them. And it’s not just squirrels; acorns have long been a part of the human diet, reportedly dating back to Ancient Greece when they were mostly eaten by lower classes during famine. This is probably because they can be toxic to humans. The tannin load in acorns, in large enough quantities, can block the body’s ability to absorb nutrients. We’ve learned to boil or soak out the tannins to make acorns more palatable (and less toxic) but that gets us back to the question: how can squirrels eat them? Without getting into the fine details of biology – let’s say, to answer in a nutshell – it’s that we are built quite differently.

This is the same reason why squirrels are able to eat mushrooms that would be harmful to humans. On that biological level, squirrels have shorter digestive tracts than humans, which allows them to eat food that would otherwise be toxic. The food spends less time in their systems, at least compared to the amount of time it would take to move through a human body, so only very small amounts of toxins need to be dealt with.

There is an oft-quoted report from a famed mycologist (someone who studies fungi), the late Dr. John Rippon, which gets to the molecular level of why squirrels can eat mushrooms. To oversimplify a bit for the sake of brevity, one of the toxins in mushrooms, that breaks down in our stomachs and can poison us, is instead bonded with a glycoprotein in a squirrel’s stomach that carries it out and keeps it from entering their bloodstream.

On a final note here, let’s make some more connections: Pam was noticing squirrels eating mushrooms for the first time in a year when there are very few acorns around, and also one of the best years we’ve seen for mushrooms. Seeing Maine’s wildlife adapt to different scenarios is always fun. Keep sending in your observations and questions. There is no nut we won’t crack!

Do you have a question for Doug? Email questions to and visit to learn more about backyard birding, native plants, and programs and events focusing on Maine wildlife and habitat. Doug leads free bird walks on Thursday mornings, 7 to 9 a.m., at the Gilsland Farm Audubon Sanctuary in Falmouth.

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