Chemical cues and group association preferences in a subsocial cockroach, Panesthia australis

Abstract

An ability to recognise and discriminate between group and non-group members is essential for most group-living species. Several different sensory modalities may be utilised for social recognition, the most notable of which is olfaction. Among insects, members of the order Blattodea (cockroaches, termites) exhibit a diverse range of social systems and provide an excellent model for examining the role of chemical communication in group discrimination. We experimentally tested the importance of chemical cues in the association preferences of the subsocial Australian wood-boring cockroach, Panesthia australis. Using a series of dichotomous choice trials, we found that individuals preferred conspecific odour cues over those of an unscented peatmoss control. We then gave cockroaches a choice between the odour cues of cockroaches from different logs, and found that they did not exhibit a preference for the cues of individuals from their own log versus those from different logs within the same locality. However, cockroaches exhibited a strong preference for cues taken from individuals from a geographically distant population. Our findings suggest that P. australis engages in group discrimination, and that patterns of association may reflect an underlying preference for unfamiliar and/or genetically dissimilar individuals in a species encumbered by restricted gene flow.