Corythucha cydoniae(Fitch), a serious pest of rosaceous hosts, did not diapause when reared in the laboratory at 20.6, 26.1, and 31.7°C in a photoperiod of 14:10 (L:D). A polynomial regression showed that egg development across temperatures was nonlinear ranging from 10 d at 31.7°C to 19 d at 20.6°C. Instar development for both sexes was similar at each temperature, and development was linear. At all temperatures, third instars required the least time for development and fifth instars required the most. Males, both single and paired, outlived females at all temperature regimens. At 20.6°C, single males lived a maximum 286 d and paired males 289 d; corresponding female cohorts lived a maximum 167 d and 140 d, respectively. Fecundity varied nonlinearly with temperature and was highest at 26.1°C, with a mean of 322 and 369 eggs produced by mated and unmated females. This previously reported univoltine species was determined to be trivoltine in Maryland. Feral adults demonstrated diapaused-like behavior in mid-September. Also, adults reared as nymphs in a glasshouse with natural, declining light diapaused with a delayed preoviposition period; whereas adults from nymphs reared in the lab under 14:10 (L:D) did not diapause. High fecundity, trivoltinism, absence of significant parasites and predators, and a wide host range contribute to the pest potential ofC. cydoniae.