1985] 
Stuart — Leptothorax curvispinosus 
79 
gated this behaviour in various Leptothorax species, including L. 
curvispinosus and L. iongispinosus, and found that these ants typi- 
cally use both tandem running and adult transport as recruitment 
techniques during emigrations. Tandem running is a chemical 
recruitment technique in which one ant leads a single follower 
between two points. The response is mediated by a pheromone orig- 
inating in the leader’s poison gland and extruded from its sting (see 
Moglich et al. 1974; Moglich 1979; Stuart and Alloway 1983). 
Workers which are led to a new nest in this manner subsequently 
become recruiters themselves and lead or carry other ants to the new 
nest. However, most colony members, including workers, are 
merely carried to the new nest, and do not otherwise become 
involved in the emigration. The unusual element in this nest emigra- 
tion system is that in many Leptothorax species tandem runs also 
occur in the reverse direction, from the new nest back to the old 
nest. Moglich could not rationalize the existence of these “reverse 
tandem runs” and, using colonies that were emigrating from a sin- 
gle occupied nest to an unoccupied nest, such recruitment appeared 
to contribute nothing to the efficiency of the emigration. However, 
if these species are frequently polydomous, emigrations may most 
commonly occur from one occupied nest to a second occupied nest, 
and reverse tandem runs could serve to recruit workers from the 
second nest to assist in the emigration. Thus, the discovery of 
polydomy may explain the existence of reverse tandem runs; and 
since this behaviour appears to be so widespread among leptothor- 
acine ants, it is possible that polydomy is also more common than 
we yet realize. 
Summary 
Leptothorax curvispinosus colonies derived from single nests in 
nature will frequently occupy multiple nests under simplified labor- 
atory conditions. Spontaneous polydomy of this type is apparently 
related to colony size. When budded, the relative distribution of a 
colony between alternative nests tends to fluctuate, and repeated 
fissions and fusions occur. These results provide further experimen- 
tal evidence for polydomy in this species. 
