Chemoecology of Oviposition in Insects of Medical and Veterinary Importance

The insects that cause or transmit human and animal disease constitute a wide range of taxa sharing a similar feeding habit, but differing in most other aspects of their life histories, including oviposition. This chapter mainly deals with oviposition or larviposition behaviour within the Diptera, since the major groups that exhibit such behaviour and that constitute pests of major medical or veterinary importance are true flies. Aggregation behaviour in bloodsucking Hemiptera is discussed briefly. Bloodfeeding groups generally oviposit at sites remote from their vertebrate hosts: mosquitoes (Culicidae) and blackflies (Simuliidae) oviposit in aquatic environments, and sandflies (Psychodidae), tsetse flies (Glossinidae), bedbugs (Cimicidae) and kissing bugs (Reduviidae) oviposit in terrestrial environments. Facultative or obligatory carnivorous Diptera, where the immature stages can be saprotrophic or parasitic on the same animals on which the adult flies feed, also locate and select oviposition or larviposition sites using chemical cues. These are the warble flies, bot flies (Oestridae), blowflies, screwworms (Calliphoridae) and flesh flies (Sarcophagidae). Knowledge of the chemoecology of oviposition in these insects lags behind that on herbivorous and parasitic insects and attractant compounds have been identified in only a few cases. A number of plant species have evolved to mimic animal odour cues to attract carnivorous fly species as pollinators. Because of the importance of these insects as vectors of human and animal disease, interest in this field has been driven primarily by a search for chemically baited traps for monitoring and control. Odour baited oviposition traps are currently used in the surveillance of a number of important pest species. Odour baited trapping for the control of pest populations may be feasible for certain species.