The effects of indol-3-acetic acid (IAA) were investigated on biological parameters of Galleria mellonella (Linnaeus, 1758) (Lepidoptera: Pyralidae) and its endoparasitoid Pimpla turionellae (Linnaeus 1758) (Hymenoptera: Ichneumonidae) reared on hosts treated with 50 to 10,000 ppm of IAA in their diet. Percent fecundity of first generation of G. mellonella females increased by 12% at 50 ppm whereas the most effective decrease, by >33%, was observed at 5,000 ppm. Percent fertility decreased by >20% at 1,000 ppm. All treatments displayed +/- 5% variations when compared to controls except for a >20% increase in corrected percent sterility at 1,000 ppm. The results did not reveal any considerable effect of IAA on egg hatching, larval and pupal developmental, or adult emergence times. The most striking effect observed was a decline in second generation pupal developmental time by >47% at 1,000 and 10,000 ppm. No dose-wise alterations were observed in adult longevity, weight, size and female sex ratio of G. mellonella. Treatment with IAA caused a slight prolongation in adult emergence and decrease in longevity of P. turionellae reared on hosts; longevity of wasps declined by >27% at higher doses. Neither wasp size nor weight displayed significant changes upon IAA treatment.