Can. En?. 108: 601-608 (1976) Life cycles of Perisrenus pallipes (Curtis) and P . pseudopallipes (Loan), parasitoids of the tarnished plant bug, Lygus lineolaris (P. de B . ) , were investigated in an alfalfa field and in uncut weeds in the Ste. Anne de Bellevue area. In 1972, P . pallipes adults emerged in mid-May and P . pseudopallipes adults emerged in late July. The incidence of parasitism in nymphal and adult stages of the tarnished plant bug, L. lineolaris, was measured. The population of the tarnished plant bug in the weeds was more heavily parasitized than the one in the alfalfa field. The ichneumonid hyperparasite Mesochorus curvulus Thomson was also found in this area.