Podisus modestus (Dallas) has one generation per year in the boreal forest of Quebec. Adults hibernate in the litter and soil from mid-autumn to late spring. Overwintered adults were found in the field until the latter part of August. Adults mated shortly after emergence from hibernation. Females mated an average of three times during the summer; the maintenance of a supply of highly fertile eggs apparently required this periodic mating. Young adults, which emerge from August to October, neither mated nor laid eggs before hibernation.The preoviposition period after first mating was 10 to 19 days. Females laid an average of 7.9 egg masses (average of 16.7 eggs per mass) at intervals of 1 to 25 days on jack pine, and on Kalmia and Vaccinium spp.Eighty per cent of the eggs hatched successfully after a mean incubation period of 15.3 days; 12% did not develop while 8% developed and were destroyed, during hatching, by other first-instar nymphs in the brood. Maturing nymphs spent an average of 7.7, 7.7, 7.8, 11.9, and 23.8 days in each of the five respective stadia, and required 59 days from hatching to adult emergence. A logistic curve describes the relationship between developmental time and temperature. First-instar nymphs required no animal food, but during each of the last four instars animal food was required for maturation. The hunting and feeding behavior, food consumption, abundance and mortality of P. modestus are also described.