Scelio spp. are important parasites of grasshopper eggs in many countries of the world. However, no information regarding these species is available for Pakistan. Therefore, a study was undertaken to record incidence, distribution, and biology of important species of Pakistan during 1970–74. Some species of Scelio such as S. hieroglyphi, S. sp. ? mauritanicus, Scelio sp. B and C, S. sp. nr. popovi, and Scelio sp. A are restricted in distribution; the first four species are host specific while others can parasitize many hosts. S. aegyptiacus, S. sp. nr. serdangensis, and S. sp. ? tristis are polyphagous and found in many areas of Pakistan. Mortality ranging between 3% and 69% of grasshopper eggs due to factors other than parasitism also occurs. Large sized egg-pods are partially parasitized as grasshopper nymphs also emerge along with the parasites, whereas in pods with fewer eggs nothing except the parasites emerge and are called fully parasitized. Of the nine species of Scelio reared from 3708 egg-pods of 16 grasshopper species, biology of S. aegyptiacus, S. hieroglyphi, and Scelio sp. A was studied which is almost identical in all the species. Immature stages comprising egg, 2 larval instars, and pupa of S. aegyptiacus are developed at 31.5°C ± 3 in 2–3, 10–11, and 7–8 days respectively. The female has the capacity to lay 121–135 eggs. Prior to oviposition, mating lasting 1–2 min takes place and a hole is drilled in the froth-plug. Freshly laid egg-pods are preferred over old during parasitization.