Egg Cannibalism Affects Growth Development, Reproduction, and Fitness of Aphidophagous Coccinellids, Hippodamia variegata, and Menochilus sexmaculatus

ABSTRACT

We investigated how egg cannibalism affects growth, development, reproduction and progeny fitness of aphidophagous coccinellids, viz. Menochilus sexmaculatus (Fabricius) and Hippodamia variegata (Goeze). Egg cannibalism provided immediate benefits to first instars by expediting molting; however, it slowed the development of later instars. The non‐cannibal later instars fed on aphid, Aphis craccivora (Koch) developed faster with greater bodyweights and immature survival (%) than the cannibals. Both egg cannibalism and aphid predation, however, did not affect adult emergence (%) with female‐biased sex ratio. For reproduction, three subsets were designed, viz. (i) Non‐cannibal adults who never ate eggs, (ii) Cannibal‐adults who ate eggs only during immature stages and after emergence fed on aphids, and (iii) Cannibal‐adults who never ate aphids. Non‐cannibal females of both species had shorter pre‐ and post‐oviposition periods with longer oviposition period, fecundity, percent egg‐viability and adult longevity. We report that cannibal females of M. sexmaculatus and H. variegata , who never ate aphids, laid 21.90 ± 4.8 and 13.4 ± 9.30 eggs, respectively, with viability of 32.30% ± 5.07% and 29.27% ± 10.33%, respectively, indicating that females cannibalizing eggs throughout their entire life span can ensure their progeny's subsistence during aphid scarcity. We conclude that egg cannibalism provides instant energy to foraging ladybirds, facilitating their survival and supplementing the development of neonates. Cannibalizing eggs can only ensure complete development to aphidophagous ladybirds in the absence of aphids. Female M. sexmaculatus was more fecund with greater cannibalistic instincts than H. variegata .