Conspecifics enhance egg production in an egg-carrying bug

Abstract

Variation in host availability and quality is likely to affect female decision making on when to lay eggs in arthropods. In the present study, we show a case in which female reproduction is limited by the availability of conspecifics in a species in which females preferably oviposit on conspecific bodies. Female golden egg bugs (Phyllomorpha laciniata; Heteroptera, Coreidae) deposit eggs mainly on the bodies of both male and female conspecifics. Bugs other than parents carry most eggs. Egg carrying is costly for individuals. A few eggs are laid on the bug's food plant, but in most habitats, those eggs do not survive owing to intensive ant predation. We explored if conspecific presence affects female egg production (eggs laid and eggs in reproductive tract) in the field. In our experiment, conspecific presence (two females enclosed with food plant) increased female egg-laying rate and egg production compared with that of females that were alone with the food plant. In nature, gaining a conspecific host is difficult, and the encounter rate of conspecifics (i.e., operational host density) is likely to be important for female reproduction. There are opposing interests between an egg-laying female and the recipient (male or female) because most eggs are dumped on individuals that are not the parent of the eggs.