Diapause incidence of the offspring of Mylabris cichorii Linnaeus was evaluated by exposing parents generation and offspring to different photoperiods and temperatures and observing the best conditions for diapause and diapause termination.Diapause associated protein was analysed by SDS-PAGE.Results revealed that diapause of M.cichorii eggs could be induced by short photoperiod.Under constant temperature at 28 ℃,the critical photoperiod for egg diapause induction was estimated between L11 and D13 and between L10 and D14.Diapause egg grew normally at early stage and entered into diapause at 18th day.Diapause of egg could be terminated by low temperature(10 ℃) treatment for 10 d.The diapause associated protein with molecular weight of 80 000 was found in diapause eggs,and expression levels of two proteins with molecular weights of 45 000 and 23 000 were raised.It is indicated that photoperiod is the critical environmental factor in the induction of diapause of M.cichorii eggs.