You said in one of your blogs that ground beetles don’t bite people (see Ground Beetles Can Become Indoor Pests), but I beg to differ. The other night I felt something biting me in my bed and when I jumped up and checked, there was a ground beetle under the covers. I have bites all on my one leg. What’s the deal? M.M., Rye, NH

Maybe I should have said that ground beetles don’t normally and purposely bite people. They are not blood feeders and have no aggressiveness towards people. You can handle a ground beetle gently without worrying that it will attack you. But you need to understand that any insect, just like any animal, will try to defend and protect itself if it feels threatened. For insects, that means either biting (if they have jaws) or stinging (if they have a stinger).

The Size of the Jaws Matters

Many smaller insects have jaws (mandibles) and may attempt to defend themselves with a bite, but their jaws are not large enough or strong enough to break through human skin. From these insects you may feel a little nip and there might be a red spot but no actual bite wound. It follows that the larger the insect and the larger its jaws, the better the chances that it could break the skin.

Ground beetles come in various sizes but since they are predators that feed on other insects, they do use their jaws to crush and kill. In other words, they are perfectly capable of biting and could do so if threatened.  I suppose that one of the larger ground beetles, one that is over an inch long, could leave a bite mark. Other insects that live among us and are capable of biting us defensively, but rarely do, are cockroaches, crickets, centipedes (arthropods, but not insects), even dragonflies.

Bedtime is Often Bite Time

Most people that are accidentally bitten by insects or spiders are bitten while in bed. A bed is a nice warm, dark place for insects to hang out. When people are asleep, they roll over on the insect or it becomes trapped in their pajamas, or somehow the insect is injured and does what it has to do, it reacts defensively.

Also consider that the bites on your leg might not have been from that ground beetle. Some other insect could have been biting you at night (bed bugs), or the bites could have been from outside earlier in the day (mosquitoes, chiggers). Also a threatened ground beetle is not likely to bite you multiple times. That ground beetle is innocent until proven guilty. And if found guilty, he could plead self-defense.

Photo credit: graftedno1 / Foter / CC BY-ND

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