none This study considers the host selection behaviour of two solitary larval endoparasitoids, Asobara tabida Nees (Braconidae) and Leptopilina heterotoma Thomson (Eucoilidae). Encounter rates with hosts were consistently low. Therefore an optimal host selections model predicted the acceptance of most host species. This was in agreement with field observations. The acceptance of parasitized hosts was also predicted by the model, suggesting that superparasitism is an adaptive strategy under field conditions. The occurrence of superparasitism was confirmed by the number of parasitoid eggs and larvae found in host larvae collected in the field.