Diapause terminations of aestival and hibernal pupae in both the leaf - mining fly, Pegomyia bicolor Wiedemann and its parasitic braconid wasp (Biosteves sp. ) under natural conditions were investigated and the effects of temperature and photoperiod on their diapause maintainance and termination were systematically studied. The results were as follows: ( I ) Under natural conditions, after all the adults of the fly emerge the parasitic braconid wasp just initiated emergence and had a tightly synchronized emergence. ( 2 ) Low temperature of 10 [degree] C was more favorable to diapause termination of P. bicolor than intermedian temperature. (Photoperiod had no effect on termination of hibernal diapause of the fly, but short daylengths seemed to be more favorable for termination of aestival diapause individuals. (4) Diapause termination of aestival individuals the braconid wasp was completely controlled by photoperiod. Diapause termination of the braconid wasp was not found at long daylights of 14 -16 h, whereas diapause was completely terminated at short daylengths of 10 ~ 13 h. However, diapause termination was the quickest at daylengths of 11-12 h. none