Mortality factors affecting the leaf‐mining stages of Phyllonorycter (Lepidoptera: Gracillariidae) on oak and birch: 2. Biology of the parasite species

Parasitic Hpenoptera attacking Phyllonorycter species mining leaves of oak and birch were studied at a Cheshire locality during 1974. The host developmental stages killed, and attacked, by each parasite species are analysed. Smaller species and males tend to kill earlier Phyllonorycter instars than do larger species and females, and certain of the endoparasites as well as the ectoparasites must discriminate between small hosts which receive haploid eggs and large hosts which receive diploid eggs. Host‐feeding is very widely practised, and facultative hyperparasitism is engaged in by all except the braconids and a few specialized chalcids. The biology of a parasite species generally allows its allocation to one of three groups according to the size of host larva that it attacks, whether it is endoparasitic or ectoparasitic, whether or not the host continues to develop after parasitization, the extent of its hyperparasitic behaviour, its reproductive capacity, and the width of its host range. Different strategies, together with different specific host and habitat preferences, provide the basis for parasite complexes of high species diversity.