none Entered Diadegma semi clausum Hellen overwinters as undevelopment pupae, the undevelopment pupae have order of magnitude characters. Laboratory studies were conducted on certain upsets of biology of Diadegma semiclausum Hellen. Photoperiodic response curve showed that critical day length was between 14 h and 16 h at 10 [degree]C under photoperiod of 10L : 14D, 12L : 12D, 14L : 10D, 16L : 8D. The emergence rate of the undevelopment cocoons should still reach to 73. 03% was exposed to 10L : 14D, and reach to 10. 67% was exposed to 16L : 8D. Diadegma semiclausum (Hellen) ( Hymenoptera: Ichneumonidae) accepted the signal for undevelopment at the pre pupa stage. All pre pupae entered undevelopment only if the young larvae had been reared in the temperature and the photoperiod for undevelopment induction till mature pupae. After 42 days cold storage about 10 [degree]C, the emergence rate of the undevelopment cocoons could still reach to 64. 13%. So there has two factors played the key role in undevelopment induction, while effect of photoperiod on undevelopment induction depended on temperature. Thus, lower temperature and shorter day length were the major factors to induce undevelopment of the parasitoid. Nov 25 2014