In the terai region of north-eastern Uttar Pradesh (NEUP) 25 species of aphids have been recorded as feeding upon a number of food plants and being available simultaneously for parasitisation byLysiphlebia mirzaiShuja-Uddin. However, only five species,viz., Hyalopterous pruni(Geoffroy),Macrosiphum (Sitobion) miscanthi(Takahashi),Melanaphis sacchari(Zehntner),Rhopalosiphum maidis(Fitch) andSchizaphis graminum(Rondani) were parasitised to varying degrees on seven food plant species. The natural parasitism of the aphid species feeding onPennisetum glaucumandSorghum bicolorwas higher than on other food plants. The highest extent of parasitisation was recorded onR. maidisfollowed byM. sacchariandS. graminumon one or other food plants. Significantly moreR. maidis/P. glaucumwere parasitised than any aphid and host plant combinations. The aphid hosts as well as the food plants significantly influence the degree of parasitism. The cereal crop habitat was highly preferred byL. mirzaiduring September to January when large areas in NEUP were cultivated with cereal crops that provided adequate host resources. Later on, its incidence decreased to zero level in April due to plant senescence which induces the aphids to migrate from the crop, prior to the crop being harvested.