With widespread planting of Bt cotton and an associated reduction in the use of broad-spectrum insecticides, the mirid bugs Apolygus lucorum (Meyer-Dür) and Adelphocoris suturalis Jakovlev (Hemiptera: Miridae) become major pests of cotton in northern China in recent years. Both species overwinter as diapausing eggs that may enhance ability to survive the cold winter. The effects of photoperiod and temperature on diapause induction in A. lucorum and A. suturalis were investigated under laboratory conditions. Egg diapause was induced primarily by short photoperiod. Temperatures ranging between 17 and 26°C had little effect on diapause induction for both species. The impact of photoperiod (x) on diapause incidence (y) was described with modified Michaelis-Menten models y = 1.1(14 - x)/(14.82 - x) for A. lucorum and y = 1.07(14 - x)/(14.79 - x) for A. suturalis. The critical photoperiod for diapause induction in the first instars of parental A. lucorum and A. suturalis calculated from the models above was almost identical, at 13.3 h (13 h, 18 min) in a 24-h cycle. The parental nymphal stage was sensitive to short photoperiod for diapause induction in both species, with the first-instar nymphs the most sensitive. The sensitivity to short photoperiod decreased gradually as the A. suturalis nymphs developed, whereas the sensitivity dropped sharply at the second instar of A. lucorum. The adults of both species exhibited little sensitivity to photoperiod for diapause induction.