Effect of host instar and temperature on fitness-related traits in the solitary endoparasitoid, Meteorus pulchricornis

Meteorus pulchricornis is a parasitic wasp, which plays an important role in the biological control of lepidopteran pests. Through assessment of the effect of host instar and temperature on fitness-related traits of M. pulchricornis, this study ascertained the establishment potential of M. pulchricornis in the fields. Results showed that M. pulchricornis accepted Spodoptera exigua for oviposition and the progenies developed successfully in hosts of all ages at three constant temperatures, 20°C, 25°C and 30°C. Parasitoid survivorship from oviposition to adult eclosion was highest at 25°C, followed by 20°C and 30°C. Cocoon weight and hind tibia length differed significantly when the parasitoid was exposed to 20°C, 25°C and 30°C. The fitness-related traits of M. pulchricornis did not increase linearly with the host age at different temperatures. The host quality was found to be optimal at intermediate host instars, which the female parasitoid preferred to parasitize. The larval development rate increased with temperature in a linear fashion up to 30°C. The threshold for larval and pupal development of M. pulchricornis was 4.2°C and 1.6°C, respectively. These results have implications for predicting the population dynamics of M. pulchricornis in situ and optimizing mass rearing of the parasitic wasp under laboratory conditions.