Trichogramma pretiosumRiley andT. exiguumPinto and Platner were compared in a temperature study at five constant temperatures of 15, 20, 25, 30, and 35°C. Developmental time of both parasite species in host (Heliothis virescens[F.]) eggs decreased with increases in temperature.T. exiguumdeveloped faster thanT. pretiosumat 25 and 30°C, but not at 20°C.T. pretiosumcompleted development at 35°C, butT. exiguumdid not. Additionally,T. pretiosumfemales lived longer thanT. exiguumfemales at 20 and 25°C; longevity decreased for both species with increase in temperature. Females outnumbered males at all temperatures. There was no significant difference between species in number of females or in number of parasites completing development per host egg.