In a laboratory test, we compared diapausing adult tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), from Stoneville, MS, and Springfield, IL, for their ability to break diapause when kept at 25°C on a nutritious food source (broccoli, Brassica oleracea variety botrytis L.) under a diapause-maintaining photoperiod of 10:14 light:dark hours. The temperature, photoperiod, and food simulated environmental conditions in the mid-South region during December when overwintering tarnished plant bugs on blooming winter hosts break diapause. It was unknown if plant bugs from areas such as Springfield (upper Midwest) in which the winters are too cold for hosts to be available also had the ability to break diapause under a diapause-maintaining daylength. One-day-old diapausing adults from Stoneville and Springfield were kept in environmental cabinets for 5 weeks. Males and females from both locations were dissected at weekly intervals to determine their reproductive status. Diapausing adults from both colonies and both sexes terminated diapause. Greater percentages of males and females from Stoneville terminated diapause each week compared to those from Springfield, and the differences were significant in four of the 5 weeks for males and three of the 5 weeks for females. The results showed that the presence of winter hosts in the mid-South has probably selected tarnished plant bugs for more rapid emergence from diapause. The importance of more rapid emergence from diapause to plant bug populations in the mid-South is discussed.