Abstracts are listed in alphabetical order by the last name of the senior author.
Agricultural Research Center, Kansas State University, Hays, KS. jpmi@ksu.edu
Egg cannibalism is common among aphidophagous coccinellids that lay clustered eggs. Neonate larvae may improve their survival probability by cannibalizing sibling eggs prior to dispersal in search of prey. Egg-clustering facilitates sibling egg cannibalism and may represent a form of maternal care that improves the survival of early-hatching larvae at the expense of late-hatching larvae. We examined sibling egg cannibalism behavior in three aphidophagous coccinellid species that lay clustered eggs: Cycloneda sanguinea L., Harmonia axyridis Pallas, and Olla v-nigrum Mulsant. Newly hatched larvae of all three species delayed dispersal from clusters when sibling eggs were available for cannibalism and consumed all late-hatching and/or non-viable eggs within clusters before dispersing. There was significant variation among species in 1) the proportion of eggs laid singly versus in clusters, 2) the proportion of eggs cannibalized by early-hatching larvae and, 3) the physiological consequences of egg cannibalism for developing larvae. Both male and female larvae that cannibalized eggs molted to the second instar sooner than did their non-cannibalizing counterparts in all three species, and 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 increases in adult weight as a consequence of egg cannibalism were sex-specific. Female cannibals were heavier as adults than were non-cannibalizing females in H. axyridis and O. v-nigrum, but males had similar weights. Egg cannibalism had no detectable effect on adult weight in C. sanguinea. Therefore, our results revealed substantial life history benefits for sibling egg cannibalism behavior in all three species, although in many cases the benefits were sex-specific.
