The present work was undertaken to evaluate the influence of three cucurbit food plants,Lagenaria vulgaris, Luffa cylindricaandCucurbita maximaon the behaviour of and sex allocation by the female parasitoidTrioxys indicusat varying densities on its hostAphis gossypii.Food plant species and parasitoid density did not influence the percentage emergence of the parasitoid from mummies; however, both had a significant influence on the total number of mummies yielded or adults which emerged. Increasing parasitoid density decreased the searching efficiency of the parasitoid on each food plant fed host. The values of the interference constantmwas higher onL. cylindricaandC. maxima-fed hosts than onL. vulgaris-fed hosts which decreased the searching efficiency of the female on those food plants. K-values for mortality due to parasitism were lower onL. cylindricaandC. maximafor all parasitoid densities. More than 50% diploid eggs were deposited in the hosts feeding onL. vulgaris(54.5–67.8%) andL. cylindrica(50.3–70.3%) whereas only 35.5 to 46.9% were deposited in the hosts feeding onC. maxima.The results demonstrated a significant effect of the food plants on the performance of the parasitoid and therefore food plants should also be considered as an important factor in biological control programmes.