Egg Load and Mating Status of the Golden Egg Bug Affect Predation Risk

Abstract

Females of the golden egg bug (Phyllomorpha laciniata) lay eggs on the backs of male and female conspecifics, and surprisingly, individuals commonly carry unrelated eggs. Here, we investigate predation risk from the ant Formica rufa during two reproductive stages of the golden egg bug: egg carrying and mating. Ants and an egg-loaded bug were enclosed with an unloaded bug, with a mating pair, or with a mating pair and an unloaded bug. Both mating and egg carrying increased predation risk. Mating increased predation risk because mating pairs were attacked more often than single egg-loaded bugs. When a mating pair was enclosed with an egg-loaded bug and an unloaded bug, the pair was attacked significantly more often than the two single individuals together, even though ant visitation rates did not differ among prey items. Ants attacked egg-loaded bugs significantly more often than unloaded bugs. Egg-loaded individuals suffered lower predation risks when in the presence of a mating pair than when in the presence of a single unloaded bug. Thus, predation risk depends on the mating status of nearby individuals. In the field, single individuals are often found with mating pairs; this observation could be explained if individuals decrease their predation risk by associating with preferred prey.