Apolygus lucorum (Meyer-Dür) and Adelphocoris suturalis Jakovlev (Hemiptera: Miridae) are the major pests of cotton because of the widespread adoption of Bt transgenic cotton in China and an associated reduction in pesticide use. The effects of short-term heat stress on the survival and fecundity of the two plant bugs were studied to understand changes in the biological characteristics of plant bugs encountering high temperature stress. The egg hatch rate, nymph survival rate, and reproduction of A. lucorum and A. suturalis in incubators were evaluated after the eggs and nymphs were exposed to 27, 30, 33, 36, or 40℃ for 4 h each day. Within the range of 27 to 40℃, the egg hatch rate of A. lucorum increased from 84.25% at 27℃ to 94.69% at 30℃, then decreased to 44.30% at 40℃; whereas the egg hatch rate of A. suturalis increased from 79.27% at 27℃ to 87.90% at 30℃, then decreased to 60.24% at 40℃. After exposure to 40℃ for 4 h, the egg hatch rate of A. suturalis was higher than that of A. lucorum; this indicated that the heat tolerance of A. suturalis eggs was significantly higher than that of A. lucorum. The nymph survival rates of both species decreased with an increase in temperature. Within the range of 30 to 40℃, the nymph survival rate of A. lucorum decreased from 70.47% to 0%, whereas that of A. suturalis varied from 69.65% to 16.74%. Furthermore, female reproduction of both species was affected by high temperature. The mean egg number of A. lucorum adult females increased from 64.78 at 27℃ to 70.03 at 30℃, then decreased slowly. A. lucorum did not lay eggs at 40℃. There was not a significant difference among the mean numbers of eggs laid by A. suturalis females from 27℃ to 36℃. However, exposure to 40℃ for 4 h each day resulted in a mean egg number of 20.75 for A. suturalis. In addition, duration of the nymphal stadia of A. lucorum was extended from 11.01 days at 27℃ to 13.67 days at 36℃ exposure. For A. suturalis, the duration of the nymphal stadia was extended from 13.05 days at 27℃ to 16.58 days at 40℃ exposure. The longevity of both sexes of A. lucorum adults decreased 2 to 4 days with exposure to 27℃ and 36℃, respectively, whereas the longevity of both sexes of A. suturalis adults decreased 11 to 13 days with exposure to 27℃ and 40℃, respectively. In conclusion, the egg hatch rate, survival rate, and reproduction of A. lucorum and A. suturalis significantly decreased after exposure to higher temperatures. However, A. suturalis was more adapted to 40℃ than A. lucorum when both survival and fecundity were considered. The adaptive divergence of tolerance to extreme high temperature may be an important factor differentiating seasonal dynamics and distribution of these species in cotton fields.