Aggregation in yellow mealworms,Tenebrio molitor L. (Coleoptera: Tenebrionidae) larvae : II. Observations and...

Evaluation of the lactic acid attraction of individual and grouped larvalTenebrio molitor L. in an olfactometer indicated that olfaction is unlikely to be the chemoreceptive mode governing substrate choice or aggregation of these insects. High-magnification videotaped sequences of mealworms on treated and control filter papers indicated that larvae sample the substrate by rapidly probing with mouthpart palpi in a manner similar to the leaf sampling of certain caterpillars. The reception of lactic acid stimuli may therefore involve contact chemoreceptors. The larvae frequently touch each other in a similar manner. Bioassays comparing the cumulative frequencies of distributions of mealworms on control and lactic acid-treated filter papers indicated significant differences, with higher density clusters being found on the treated papers. Comparison of the control distribution with the expected distribution revealed an innate tendency to aggregate. The implications of these results are discussed with regard to the formation of mealworm clusters in the environment.