Strange ant behavior (Cheryl, New York, USA)


I would like to know if there is any sense to make out of the strange behavior I witnessed an ant making in my house.

I live in Long Island, NY and I guess the type of ant was a regular black carpenter ant. The first thing that struck me odd was that it had a very narrow thorax, almost like it was pinched in...But that might be 100% normal and I've just never looked that hard at an ant before.

The second thing that struck me odd was that it was standing still and seemed to be jittering its legs while they were planted on the floor, almost like wobbling them. I thought maybe it was neurological damage? Poison? I don't know.

I decided to get some cookie crumbs and a plastic cup so I can try to feed it and observe it for a little while. It did eat a bit which made me feel better. The next strange behavior I saw was that it started grooming the hell out of itself, almost manically as if it was on speed, then it proceed to bite at the bottom tip of it's abdomen. It was freaky; I thought maybe it was pregnant and ready to pop out some eggs or something. I don't think it was, though. It was really weird. I hope he wasn't sick or poisoned. I named him Mercury. I got grossed out from lying on the kitchen floor to watch all this and let it go off into the sunset...


Cheryl Cusimano


Hi Cheryl,

The ant you found was very likely a carpenter ant, but without a more thorough description or any photographic cues, this might be hard to confirm. The "narrow thorax" you observed could have been either the petiole of an ant (the small segment joining the mesosoma and gaster that gives all ants and many other hymenopterans the appearance of having a "waist") or the constricted petiolar segment of a parasitoid wasp. Ensign wasps (family Evaniidae), for example, superficially resemble black carpenter ants and are familiar (if less common) interlopers in domestic settings given their predatory association with cockroaches.

The jittering movement is likewise difficult to explain without further observation. If the insect was indeed an ensign wasp, you might compare this behavior with descriptions of the wasp's peculiar bobbing movements, which involve jerking its abdomen up and down like a hatchet.

The meticulous grooming behavior you observed is characteristic of almost all insects, especially after a meal. Whether this particular individual was an ant or a wasp, obsessive self-grooming would not be unexpected following close inspection of foreign objects like cookie crumbs or plastic cups.

Hope this helps,

Alexandra Westrich & the AntAsk Team

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