none The objectives of this study are to evaluate the parasitism rate (n sub(p)) and search rate (a') of the corn aphid parasitoid Lysiphlebia mirzai) Shuja-Uddin 1975 (on the host Rhopalosiphum maidis Fitch 1856) as well as its sex allocation at different parasitoid-host ratios (R). Rising R increases n sub(p) although the rate of multiplication (number of hosts parasitized/female, M) and a' (measured as Nicholsonian area of discovery) decreases with rising R implying the presence of mutual interference. The data furnish an insight into the number of parasitoids needed to suppress the estimated aphid population. Sex ratio of F sub(1) offspring is inversely related with R indicating the desirability of having less female parasitoids per unit of host material for generating more female progeny. Reproduction; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Population dynamics; Population structure Lysiphlebia mirzai (Aphidiidae); Sex determination; Hemipteran hosts; Rhopalosiphum maidis; Parasite progeny sex allocation, parasite/host ratio effects; Population sex ratio; Progeny sex allocation, parasite/hemipteran host ratio effects Rhopalosiphum maidis (Aphidoidea); Hymenopteran parasites; Lysiphlebia mirzai; Parasite progeny sex allocation, parasite/host ratio effects