Larval cannibalism in aphidophagous ladybirds: Influencing factors, benefits and costs

The influence of food availability, food quality, size disparity and density on larval cannibalism in two aphidophagous ladybirds, Propylea dissecta and Coccinella transversalis, was studied in the laboratory. Both species were cannibalistic; however, the rate of cannibalism was greater in the former species. Cannibalism increased with reduced food availability rather than reduced food quality. Size disparity increased larval cannibalism in both species. Cannibalism rate also increased with an increase in larval density. The high rate of cannibalism by first instars was recorded at high larval density. Larvae fed conspecific eggs throughout the development were heavier than those fed conspecific larvae, but weighed less than larvae fed aphids, Aphis gossypii. Larval cannibalism was not advantageous in terms of development and body weight. However, egg cannibalism by first instars was advantageous resulting in fast development and heavier second instars.