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 investigated the dietary benefits of cannibalism for larvae of the multicolored Asian lad) beetle, Harmonia axyridis (Pallas). Cannibalism might benefit the larvae by allowing cannibals to take advantage of prey-detoxification already completed 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 recorded larval development and survivorship. In the first experiment. we fed groups of H. axyridis larvae an aphid species of intermediate quality, Aphis nerii (Boyer deFonscolombe), and prevented or permitted consumption of conspecifics of varied quality - conspecific victims had either fed upon the same intermediate quality food as the focal individual or had fed upon a high duality food. Cannibalism increased survivorship and shortened development time, and eating conspecifics that had fed upon higher-quality food further shortened early development. In a second experiment, we reared groups of H, axyridis larvae with one or both of two aphid species of poor (Uroleucon spp.) or intermediate [Aphis fabae (Scopoli)] quality, and either permitted or prevented cannibalism. Lan ae could complete development when fed both conspecifics and the intermediate quality aphid, but not on any other diet. Overall, when mixed with other foods, cannibalism allowed H. axyridis larvae to develop oil pre) that were otherwise nutrient deficient or toxic.