not in Young The developmental period, adult longevity, fecundity, age-specific survival rate (lx), age-specific fecundity (mx) and body size effects on the longevity and fecundity of Lysiphlebus fabarum (Marshall) from the population of Memuro, Hokkaido, which parasitizes the cowpea aphid Aphis craccivora Koch, were examined. The mean developmental period, adult longevity, and fecundity (20[degree]C and 16L8D photoperiod) were 11.8 days, 6.6 days, and 60.4, respectively. All progeny produced were females, indicating that the population is thelytokous. On the basis of the results, the estimated intrinsic rate of the natural increase (rm) of this parasitoid was 0.241. A positive significant correlation was found between female body size and longevity, but no significant correlation was found between body size and fecundity. Aphis craccivora (Aphidoidea): Host; Lysiphlebus fabarum (Aphidiidae): Parasite. Aphis craccivora: Hymenopteran parasites, Lysiphlebus fabarum, Japan, Hokkaido, Memuro, parasite development and reproduction; Lysiphlebus fabarum: Size, Body size effects, Reproduction, Reproductive characteristics, Fecundity, Age-specific fecundity, Development, Developmental period, Longevity, Adult longevity, Hemipteran hosts, Aphis craccivora, Population dynamics, Intrinsic population increase rate, Survival, Age-specific survival rate, Japan, Hokkaido, Memuro. Arthropods; Hymenopterans; Insects; Invertebrates; True Bugs. none