A comparative study of larval cannibalism in three species of ladybird

Abstract

Abstract.1. Cannibalism was studied under laboratory conditions in three species of Coccinellidae (Coleoptera):Cycloneda sanguinea,Olla v‐nigrum, andHarmonia axyridis. Larval cannibalism varied among species,C. sanguinea >H. axyridis ≥ O. v‐nigrum.2. Larvae of all species cannibalised more in response to reduced food availability (14 h starvation daily) than in response to reduced food quality (dryEphestiaeggs).3. Larvae ofH. axyridiscannibalised siblings at lower rates than non‐siblings, but larvae ofC. sanguineaandO. v‐nigrumdid not. Rates of cannibalism increased significantly with increasing size disparity among larvae of all three species.4. Cannibalism inC. sanguineaandH. axyridis, but not inO. v‐nigrum, increased with larval density, suggesting that not all attacks on conspecifics are driven by hunger.5. Costs, not benefits, were the predominant effects of exclusively and partially cannibalistic diets. A diet of conspecific eggs yielded survival equivalent to theEphestiaegg diet forH. axyridisandO. v‐nigrum, but developmental time was extended and adults were smaller. Larvae ofC. sanguineahad superior survival and faster development on conspecific eggs than on theEphestiaegg diet. OnlyH. axyridislarvae survived as well on diets comprised exclusively or partially of conspecific larvae as onEphestiaeggs, although they developed more slowly.