Discrimination of nestmate larvae by the ant Leptothorax longispinosus

Abstract

Laboratory colonies of the ant Leptothorax longispinosus were presented with 10 larvae each from their own nest, conspecific larvae from a nest collected from the same site of origin, and conspecific larvae from a nest collected from another site in the same geographical region. Workers preferentially retrieved larvae from their own nest over those from nests obtained at the same site and other sites. Non-nestmate larvae from the same site were not preferred over those originating from other collection sites. Thus, L. longispinosus workers discriminate among conspecific larvae and preferentially retrieve nestmate larvae. Results of experiments involving CO2-anaesthetized larvae or larva-sized silicone "baits" suggest that the discriminator substances underlying nestmate larva recognition are chemical in nature and are borne on the larval cuticle. Further, those chemical attractants are present on material found within the ant's nest. In a final series of experiments, nestmate larvae were placed in contact with non-nestmate conspecific larvae or with larvae of a congener (Leptothorax ambiguus). Again workers preferred nestmate larvae, and preferred conspecific over allospecific larvae. However, there was no evidence that contact with nestmate larvae enhanced the acceptance of either conspecific or allospecific larvae, nor that contact with non-nestmate larvae diminished the acceptability of actual nestmate larvae. These findings suggest that any cues transferred via contact are insufficient to overwhelm a larva's own underlying recognition signature or that workers selectively attend to familiar cues.