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