none Listronotus bonariensis; HYMENOPTERAN-PARASITES; Microctonus hyperodae; Parasite fecundity, longevity & oviposition, control implications Microctonus hyperodae; EGG-LAYING; Oviposition in coleopteran hosts, temperature effects; FECUNDITY-; EGG-NUMBER; Ovarioles, fecundity assessment; LONGEVITY-; COLEOPTERAN-HOSTS; Listronotus bonariensis; Parasite fecundity, longevity & oviposition, control implications The reproductive tract of the parasitoid Microctonus hyperodae was found to comprise 6.1 +- 0.2 ovarioles containing a total of 40-60 oocytes. After oviposition into its host Listronotus bonariensis, the parasitoid's egg volume increased by 205 times prior to hatching. At 19.1 degree C ovipositing M. hyperodae survived for a mean 21 +- 4 days and laid a mean of 48 +- 8 eggs. M. hyperodae collected from Colonia, Uruguay laid a mean of 62 +- 15 eggs which was significantly more than the other ecotypes. Under caging conditions with an ample supply of hosts, M. hyperodae laid 51% of its eggs in the first 72 hours and on average 41% of the species' life-span occurred after the exhaustion of its egg supply. Minimum temperature for M. hyperodae oviposition was found to be c. 5 degree C; beyond this the rate of increase in egg-laying was approximately linear until 30 degree C whereafter the rate fell abruptly. There was effectively no egg-laying at 39 degree C. The parasitoid showed no preference for one host sex or the other either in the laboratory or under field conditions. Compared to other Microctonus spp., M. hyperodae appeared to show low fecundity and high longevity. The adaptive implications of this are discussed.