Approximately 20% of 10 species of coccinellids collected from alfalfa, turnips, corn, and weed fields from December 1965 through June 1967 were parasitized byPerilitus coccinellae(Schrank). Populations of adultP. coccinellaepeaked at about 54 per 100 sweeps during August and September. The 2 most common coccinellids collected wereColeomegilla maculata(DeGeer) andHippodamia convergensGuérin-Méneville. The rate of parasitism varied with the size of the host species.