How to tell whether ants are from the same colony? (Rex, Chicago, IL, USA)

I've been feeding some ants on my desk which I believe to be Tapinoma sessile. I tracked them quite a long way to the front door of my house. Recently I discovered that some of the ants are coming from the opposite direction from my window which is halfway around the house. Is there a way to tell if they are from the same colony?
I've read that T. sessile is very tolerant of other ants so I don't expect any fighting. I tried to see if the ants coming from one way would go the other way. This leads me to my next question, would ants from the same species but different colonies be able to recognize each other's pheronomes as if it were their own?


Hi Rex!

Thanks for contacting us at AntAsk! To tell whether ants are from the same colony, I would suggest that you carefully collect one ant from one of the groups and place it in the other group. Of course, if fighting takes place, the ants were from different colonies. But also if the ants start inspecting each other carefully with their antennae and might even pull each other at the mandibles, this suggests they are from a different colony. If the ants act as nothing has happend and the experimentally introduced individual just runs with the others, they might indeed be from the same colony.

Researchers often use behavioral observations to determine colony boundaries. Other tools are the analysing cuticular hydrocarbons and/or genetic markers such as microsatellites. Social insects such as ants use low-volatile chemicals (usually hydrocarbons) that are present on the cuticle to distinguish nestmates from foreign individuals. If the hydrocarbons of two ant colonies are very similar, which might be due to the fact that the colonies are related to some extend, ants might have a hard time to determine who is a nestmate and who is not.

I hope this answers your questions!
All the best,
Steffi Kautz & the AntAsk Team

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