Selection on host age and size, reproduction ability, adult longevity and offspring sex ratio of Microplitis tuberculifer were studied. The results indicated M . tuberculifer preferred to parasitize the 1st or 2nd instar of Pseudaletia separata larvae. The selection indice of M. tuberculifer on 1st, 2nd and 3rd instar P. separata larvae were 0.42, 0.54 and 0.05 respectively, but it didn't parasitize the larvae over 3rd instar. The wasp could copulate and parasitize on the day of its eclosion. At 19 - 25[degree]C , one female wasp could parasitize 30 M . tuberculifer larvae on average, 89 larvae at most. Under this temperature range, longevity of female wasp was 6d on average and 13d at most, and its offspring sex ratio ( [male] : [female]) was 1 : 1.02 - 1 : 1.27. Pseudaletia separata (Noctuidae) : Host Microplitis tuberculifer (Braconidae) : Parasite Techniques; Genetic techniques; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts Microplitis tuberculifer; Artificial selection; Lepidopteran hosts; Parasite biology & response to selection; Pseudaletia separata Pseudaletia separata; Hymenopteran parasites; Parasite biology & response to selection; Microplitis tuberculifer none