Last night I discovered many ants entering my house through a window with an imperfect seal. I placed a poison ant bait on the window sill and within seconds they were feasting on it. This morning I noticed there were still many ants near the bait, but they were all bypassing it as if they were somehow warned to stay away. Do they have such a signal? If so, how would they know the bait is a problem? If not, what could cause them to be so interested last night and not interested at all today? (I can see that there is still plenty of food inside.)

Update: after a little bit more research, I decided that ants do not have a "stay away" signal, and that the only explanation for ignoring the bait would be a stronger scent trail leading somewhere else. Last night when I opened the window I found the jackpot. There was some sort of sticky substance all over the bottom of the window, and hundreds of ants celebrating the find. My conclusion is this was much more attractive than the bait, even though it was merely an inch away from their path.


It is a long time since I set in a Computer Sci (AI) talk about this…. This explains it a bit.

  • Once ants have eaten they return to the nest.
  • On the way back to the nest they put down a scent.
  • This scent fades with time.
  • Most ants follow the scent.
  • (A few ants walk randomly to find new food, or a new faster way to the current food.)

So if the agents eating your poison bait do not make it back to the nest, there is no scent trail leading to the poison for more ants to follow. But the ants that went round the bait to find other food, did make it back to the next, so setup a new sent trail.

If a poison kills the ants quickly, the customer is likely to see dead ants and therefore buys more of the poison. However a poison that kills the ants slowly, so the ants don’t die until they get back to the next, is likely to get more of them, as there is now a strong sent tail to the poison.

  • $\begingroup$ interesting answer... makes sense - are there any available references that you could cite to back up the answer? It would improve its strength. Thanks for your efforts! $\endgroup$ – Vance L Albaugh Jun 21 '16 at 11:36
  • $\begingroup$ @VanceLAlbaugh, sorry nothing better then what anyone can find with google themselves. But I have shown that a "keep away" signal is not needed to enable ant to "keep away" from something that kills them quickly. $\endgroup$ – Ian Ringrose Jun 21 '16 at 11:54
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    $\begingroup$ I'm pretty sure the ant bait I used takes 1-2 days to kill the ant, so there should be enough time for them to get back to the nest. However, your implying that there was a stronger scent to a different food source turned out to be correct. $\endgroup$ – TTT Jun 21 '16 at 14:18

Yes, ants communicate with members of their colony by releasing specific chemicals and pheromones to indicate danger. The ants that entered your house and ate the poison must have released a "danger" chemical, thereby warning the rest of the colony. I suggest sticky traps for capturing the remaining ants.

Here is an interesting article on the matter.

  • $\begingroup$ Sorry, I'm not convinced. The article you referenced talks about a scent that only living ants have, which fades out about 40 minutes after death. Once the living scent is gone the ants know to remove them from the colony. It doesn't speak of a danger scent. I believe some ants do have a "danger" scent, however my understanding is that it's the opposite of "stay away". I believe it means "come here and fight, something is attacking us". So if the "danger scent" was released, I would expect more ants to appear (and perhaps frantically take the bait?), not avoid the bait altogether. $\endgroup$ – TTT Jun 21 '16 at 3:22

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