Among social insects, foraging behaviour serves as a principal link in
the translation between individual-level performance and colony-level
success. Because nest size has been implicated as an important variab
le in that translation, foraging behaviour was studied in an ant speci
es that spontaneously changes its nest size over the summer. Effects o
f queen presence/absence and nest size on speed, linearity and directi
onality of movement were measured for (1) a series of undisturbed nest
s and (2) nests that were altered in a pseudo-mutant experiment to sim
ulate nest fractionation in the field. Ants looking for food behaved d
ifferently for each of these three measures than did ants carrying foo
d to the nest. Furthermore, nest size had strong effects on the behavi
our of ants, but queen presence/absence was not a consistently importa
nt factor. Our results show that an ant forager's behaviour reflects t
he social milieu within her nest, even when she is outside that milieu
. (C) 1996 The Association for the Study of Animal Behaviour