Nutritional benefits of cannibalism for the lady beetle Harmonia axyridis (Coleoptera : Coccinellidae) when prey quality is poor

Cannibalism, a widespread phenomenon in nature, can both reduce competitors and introduce a high-quality food into the cannibal's diet. We investigate d the dietary benefits of cannibalism for larvae of the multicolored Asian lad) beetle, Harmonia axyridis (Pallas). Cannibalism might benefit the larv ae by allowing cannibals to take advantage of prey-detoxification already c ompleted by the victim or the different, and perhaps more diverse, feeding histol) of the victim. In two laboratory experiments we reared H. axyridis larvae with aphid pre), and with or without conspecifics to consume, and re corded larval development and survivorship. In the first experiment. we fed groups of H. axyridis larvae an aphid species of intermediate quality, Aph is nerii (Boyer deFonscolombe), and prevented or permitted consumption of c onspecifics of varied quality - conspecific victims had either fed upon the same intermediate quality food as the focal individual or had fed upon a h igh duality food. Cannibalism increased survivorship and shortened developm ent time, and eating conspecifics that had fed upon higher-quality food fur ther shortened early development. In a second experiment, we reared groups of H, axyridis larvae with one or both of two aphid species of poor (Uroleu con spp.) or intermediate [Aphis fabae (Scopoli)] quality, and either permi tted or prevented cannibalism. Lan ae could complete development when fed b oth conspecifics and the intermediate quality aphid, but not on any other d iet. Overall, when mixed with other foods, cannibalism allowed H. axyridis larvae to develop oil pre) that were otherwise nutrient deficient or toxic.