The larval endoparasitoid Microplitis mediator Haliday is described for the first time in the Neotropical Region, parasitizing the wheat armyworm Mythimna (Pseudaletia) sequax Franclemont. Females successfully parasitized the four first instars of the host, with a significant preference for the second and third, in relation to either the first or fourth instars. No parasitoids emerged from caterpillars parasitized in the fifth and sixth instars. Development of M. mediator was determined at four constant temperatures between 15°C and 30°C. The duration of the egg-larval stages varied from 32.3 days at 15°C to 8.0 days at 30°C. The pupal stage lasted 24.3 and 5.1 days at 15°C and 30°C, respectively. Development of the parasitoid from oviposition to adult emergence required the total of 251.3 degree-days (DD) above the threshold of 10.3ºC. At 20°C, longevity of females was significantly shorter when kept in oviposition activity (16.8 ± 1.81 days) in comparison to females kept without hosts (29.7 ± 1.83 days). Parasitoid females remained reproductively active until one day before death, and parasitized an average of 60.6 ± 8.40 second instar hosts during their adult life, with an average of 3.9 parasitized caterpillars/day.
Insecta; endoparasitoid; thermal requirement; biological control
