Studies were conducted on the biology of the recently described Goniozus sensorius Gordh (Hymenoptera: Bethylidae), a gregarious ectoparasitoid of Diaphania indica (Saunders) (Lepidoptera: Pyralidae). Eggs are laid after temporarily paralyzing the host. Mean development time from egg to adult is 11.96 days at 26.43 and 65.08% r.h. The female lays an average of 50.1 eggs during its life time and parasitizes 7.26 hosts on average. The sex ratio is 1:3.91, males:females. Mean adult longevity is almost similar for males (8.55 days) and females (9.81 days). Aphanogmus fijiensis (Ferriere) (Hymenoptera: Ceraphronidae) was recorded as a hyperparasitoid through G. sensorius.