Differential egg cannibalism by hatchlings in a burrower bug: Trophic and viable eggs

In animals that exhibit cannibalism among relatives, victim discrimination by cannibals can affect their inclusive fitness. Moreover, when viability varies among potential victims, cannibals are expected to consume less viable individuals. In the burrower bug Adomerus triguttulus (Motschulsky), females exhibit parental care that includes the provision of trophic eggs. These eggs are deposited during egg care and are consumed by nymphs shortly after hatching. Occasionally, early‐hatched nymphs also feed on viable sibling eggs. To test whether hatchlings discriminate between trophic eggs and viable eggs that contain embryos at different stages of development, we conducted feeding‐preference experiments to determine whether cannibalistic nymphs show a preference for victim eggs when they are arranged in a circle or in a clump. Hatchlings exhibited a consistent preference for trophic eggs when both trophic and viable eggs containing fully developed embryos were available. They also showed a preference for viable eggs with less developed embryos compared to eggs that contained fully developed embryos. However, when trophic eggs and viable eggs with less developed embryos were presented together, hatchlings preferentially attacked the viable eggs, although the preference was obscure in the clump condition. The results suggest that signals or cues from fully developed embryos modulate cannibalistic interactions.