Aggregation in yellow mealworms,Tenebrio molitor L. (Coleoptera: Tenebrionidae) larvae : I. Individual and group attraction to frass and isolation of an aggregant.

Late-instar larvalTenebrio molitor L. were found to be attracted to aqueous extracts of conspecific larval frass. The attraction was evident at both the individual and group level. The attraction of larval groups to frass indicated the possibility of an aggregation pheromone that would be chemically distinct in the mealworm environment. Chemical analysis of short carbon chain acids present in both the mealworm frass and the diet indicated that lactic acid was present in the mealworm frass only. Acetic acid was identified in both the diet and the larval frass. Larvae aggregated on filter papers treated with aqueous frass extracts that had been dried and also on those freshly wetted. The larvae also aggregated on dried or freshly wetted papers treated with lactic acid, but failed to aggregate on freshly wetted papers or dried papers treated with acetic acid. The role of excreted lactic acid as a discriminant of already infested and, therefore, safer environmental regions is discussed.