Females of the golden egg bug, Phyllomorpha laciniata Vill (Heteroptera, Coreidae), lay their eggs on the backs of male and female conspecifics. Eggs survive poorly in nature unless being carried by living conspecifics. The most likely evolutionary explanation to egg carrying is that individuals carry their own eggs. Thus, egg carrying has been considered to be paternal care. In this thesis I show that it is unlikely that the peculiar breeding system of these bugs has evolved or is maintained as a paternal care strategy. Firstly, females are prone to lay eggs on the backs of any individual available. Thus, males commonly receive eggs they have not fertilised. Secondly, males do not prefer to accept eggs from females they have mated with. Instead, oviposition attempts are sometimes resisted and high certainty of paternity do not influence males to carry their own eggs. Thirdly, paternity analyses with microsatellite DNA markers revealed that half of the males analysed did not carry any eggs of their own, and only 21% of the eggs carried by the remaining males were fertilised by them.

When conspecifics receive eggs involuntarily or if egg carrying is costly, then female egg carrying may be regarded as intraspecific parasitism. I found no support for egg carrying being costly, either in terms of increased predation or decreased mobility. However, as eggs survive poorly unless being carried, females bring other individuals to carry their eggs. Especially, when a female utilises resisting individuals as oviposition sites, she is behaving like an intraspecific parasite.