Feeding in epiphytic, carnivorous insects: resource partitioning and the avoidance of intraguild predation

Abstract

The gut contents of larval Enallagma cyathigerum (Zygoptera: Odonata), Cyrnus flavidus (Polycentropodidae: Trichoptera) and Ablabesmyia monilis (Tanypodinae: Chironomidae) feeding in nature and in experimental aquaria, were analysed. The diet of C. flavidus overlapped greater with the diet of A. monilis than with the diet of E. cyathigerum. Feeding intensity and diet composition in C. flavidus and A. monilis were different in experimental aquaria with and without E. cyathigerum. Weights of their food and mean weights of their prey were lower in the presence of the latter when compared with the control, while the number of prey items was not. The proportions of active prey items in diets of C. flavidus and A. monilis were higher in the presence of E. cyathigerum but the numbers of such prey items were higher in the diet of C. flavidus only. These differences are probably caused by reduced predator mobility during feeding, not by a behavioural response from prey. Induced changes in feeding activity are considered an effect of a behavioural defence mechanism reducing the risk of intraguild predation.