Home, Sweet Smelling Home

Pharaoh ants are a small species with adults growing to about 2 millimeters, but they are rather different from many ant species in that they are quite happy with one colony living alongside neighboring colonies. Colonies are small thug, with a couple of thousand ants of which up to 10% may be queens.

They are more than happy to share our goodies, whether it is honey or toothpaste so we see them all over the place in our homes or places of work. The problem is that they produce more ants, but as they live in small colonies, this means that as one colony expands it splits into an additional colony and in a very short time you can find colonies all over your building once the first one takes a liking to it.

Our intuition would guide us to expect that the new colony group would rush off as far as they could before putting down roots to minimize foraging overlap and other sundry reasons for not having close neighbors, but that doesn’t seem to be a criterion for the Pharaoh ants. Evison et al from U of Leeds looked into their decision making process and published their results last week (1).

Ants mark their trails with pheromones so that they can get back home with their booty and not get lost. In the lab they were presented with trail choices for new nests. Some familiar trails led to new nest sites while other poorly marked ones led to even better nest sites in some cases, although some others were a bit down market.

Invariably the ants chose the familiar. If the new sites were indeed better, they would reconnoiter and decamp to take up residence later. They were rather conservative and liked their paths to have the familiar smell of their pheromones when making their corporate decisions. Not for them, the bold jump into the unknown.

  1. S.E.F. Evison, K.A. Webster & W. O.H. Hughes, J. Behav. Ecology & SocioBiol., (2012) doi: 10.1007/s00265-012-1319-2

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