The effects of Malathion, an organophosphate insecticide, on the egg production and hatchability of the adult females of Pimpla turionellae L (Hymenoptera: Ichneumonidae) reared on pupae of the wax moth Galleria mellonella L were investigated. The hatchability ratio of eggs, which are left in the host during the life cycle of P. turionellae, have became less at all concentrations (1.000, 0.100, 0.010 and 0.001 ppm). It is remarkable that the highest reduction in egg production appeared between days 25 and 40 with an average of 43% at a concentration of 0.100 ppm. A concentration of 0.010 ppm increased the egg production with an average of 14% between days 10 and 40. Galleria mellonella (Pyralidae) : Host Pimpla turionellae (Ichneumonidae) : Parasite Reproduction; Reproductive productivity; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Abiotic factors; Chemical factors Galleria mellonella; Hymenopteran parasites; Malathion effects on parasite egg production & hatchability; Pimpla turionellae; Fertilizers and pesticides; Malathion Pimpla turionellae; Egg number; Hatching success; Lepidopteran hosts; Malathion effects on egg production & hatchability; Galleria mellonella; Fertilizers and pesticides; Effects on egg production & hatchability; lepidopteran host; Malathion none