Agrotis segetum; HYMENOPTERAN-PARASITES; Cotesia telengai; Parasite biology & host specificity, laboratory study Cotesia telengai; REPRODUCTIVE-PRODUCTIVITY; Lepidopteran host larvae; DEVELOPMENT-; Time, temperature effect, lepidopteran host, laboratory study; LEPIDOPTERAN-HOSTS; Agrotis segetum; Productivity & host specificity, laboratory, temperature role; TEMPERATURE-; Development time & productivity effects, lepidopteran host in laboratory. The host suitability of Agrotis segetum Denis & Schiff., A. ipsilon Hufn., Spodoptera littoralis Boisd., S. exigua Hub., Mythimna loreyi Duponchel and Mamestra oleracea L. for the gregarious braconid Cotesia ( = Apanteles) telengai Tobias was determined under laboratory conditions. The parasitoid only completed its development in larvae of A. segetum. The percentage of successfully parasitized larvae and the mean duration of C. telengai egg-larval period were inversely related to the age of the host or host instar at parasitization. The mean number of parasitoids which emerged per parasitized larva was positively correlated with the larval age. The sex ratio was consistently high (ca. eight males to one female), independent of the host instar parasitized, as compared to 1:1 as observed frequently in field populations of this wasp. The females of C. telengai were active and produced offspring at temperatures of 15, 20, 25 and 30 degrees C. However, the mean percentage of parasitized larvae increased from 13.1 to 72% and the mean progeny per parasitoid female increased from 14.7 to 129.4 parasitoids, both significant, when the experimental temperature was raised from 15 to 30 degrees C, while their mean development time decreased from 75.5 to 19.2 days. At 25 degrees C, the virgin and mated females continued oviposition until days 16 and 17, with a lifetime total of progeny of 397.6 (SD +/- 224.7) and 611.1 (SD +/- 128.8) parasitoids respectively, reaching a maximum of 64.3 and 99.2 on day 2 respectively. none