Nest Construction and Recognition in a Gryllacridid: the Discovery of Pheromonally Mediated Autorecognition in an Insect

The mechanisms of nest building and relocation were examined in Hyalogryllacris sp. 14 (Orthoptera: Gryllacrididae). This nocturnal, thigmotactic species readily constructed silken nests in artificial shelters or 'tents'. The architecture and silk density of nests did not differ significantly between individuals, although nests of males contained significantly more silk that those of females. Disturbing the insects during photophase elicited defensive displays. Gryllacridids reoccupied their original nest significantly more often than an empty tent or the nest of a conspecific, after a night of foraging in a laboratory arena. When offered heat-treated (80 degrees C for 2 h) nests, gryllacridids showed a significant preference for those with greater amounts of silk. The heating (chemical cue elimination), tearing (tactile cue elimination), and heating-tearing of an insect's nest significantly reduced the tendency of the subject to occupy its own nest. Gryllacridids were significantly more likely to occupy nests of conspecifics that had been heat-treated than those that were untreated. They were also significantly more likely to occupy heat-treated nests to which acetone extracts from their own nests had been applied than similar nests treated only with solvent. Thus, individuals of Hyalogryllacris sp. 14 are able to relocate their own nests and avoid those of conspecifics based on a chemical cue. This study provides the first evidence of the capacity for individual or self recognition in insects or other invertebrates through a pheromone or any other sensory modality.