The natural history of Corythucha juglandis (Fitch) and Gargaphia tiliae (Walsh) (Hemiptera: Tingidae) was studied in Ontario and Québec, Canada. These univoltine species overwinter as adults in leaf litter in a state of reproductive diapause and become active in April or May. They are specific to their host plants. Adults, eggs, and nymphs of both species were collected from the underside of leaves of host plants. The reproductive systems of both male and female, as well as eggs, nymphs, and operculum of the eggs of the two species, are described and illustrated. Fecundity, incubation period, development of nymphs, feeding, mating, and oviposition were studied. Mating was end-to-end at an angle of 35–40°. The reproductive potential, oviposition pattern, and site selection in the two species were investigated. Parental care of eggs and brood of G. tiliae is also reported and illustrated. Ocelli, true spermathecae, true egg micropyles, and true egg burster are absent in the two species. Fertilisation takes place before chorion formation. Adults, nymphs, and new generation aggregate on the underside of leaves of their host or nearby deciduous plants. In October they fly a short distance to overwintering sites within leaf litter.