We examined the nature of sibling egg cannibalism behavior and its developmental consequences in three aphidophagous Coccinellidae that all lay clustered eggs: Cycloneda sanguinea L., Harmonia axyridis (Pallas), and Olla v-nigrum Mulsant. There was variation among species in the proportion of eggs laid singly versus in clusters (C. sanguinea > H. axyridis ≈ O. v-nigrum), the synchrony of egg hatch within clusters (H. axyridis > C. sanguinea ≈ O. v-nigrum), and the proportion of eggs cannibalized by early-hatching larvae (O. v-nigrum > C. sanguinea > H. axyridis). Single eggs were cannibalized at lower rates than clustered eggs in all three species, and cannibals delayed dispersal from clusters until all unhatched eggs were consumed. In all three species, the number of eggs cannibalized was negatively correlated with the proportion hatching synchronously (within 10 min). Egg cannibals survived to adulthood at the same rate as noncannibal larvae in H. axyridis and O. v-nigrum, and at a higher rate in C. sanguinea. In all three species, larvae that cannibalized eggs as neonates molted to the second instar sooner than did their noncannibalizing counterparts, regardless of gender. This translated into reduced total developmental time for both sexes in H. axyridis, but only for males in C. sanguinea and only for females in O. v-nigrum. Adult females weighed significantly more than adult males in all three species and female cannibals were heavier as adults than were noncannibalizing females in H. axyridis and O. v-nigrum, whereas males had similar weights. Egg cannibalism had no effect on adult weight in C. sanguinea, but the rearing diet was not optimal for this species. We conclude that the benefits of sibling egg cannibalism accrue in a gender-specific manner such that females potentially gain more than males, but only if the subsequent larval diet is of sufficiently high quality.
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Vol. 97 • No. 4