Studies on the bionomics ofTrioxys (Binodoxys) indicus [Hym.: Aphidiidae]: Effect of population densities on sex ratio

The effect of different population densities ofTrioxys (Binodoxys) indicus Subba Rao & Sharma and its hostAphis craccivora Koch, on the sex ratio (female: male) of the parasitoid was observed. The sex ratio (favouring female sex) increased with increase of host density. Parasitoid contamination priciple and behavioural responses of female parasitoid in addition to environmental factors were applied to explain the results. Results clearly indicated that fewer parasitoid releases might be better at any immediate release site for the production of maximum female progeny in this species.