The pentatomid bug, Andrallus spinidens F. is anticipated as a pest control agent to lepidopteran larvae. We tried to develop a laboursaving rearing method of A. spinidens on artificial diet. The diet developed for P. maculivientris and P. sagitta (De Clercq and Degheele, 1992) was mixed with silkworm pupa powder, sealed with Parafilm, and molded as a artificial diet piece. Using stored frozen this diet pieces, we were able to reared A. spinidens with high survival rates. And to obtain the eggs of the A. spinidens throughout the year, we examined the effect of the day length condition on the spawning of A. spinidens under 25°C rearing condition. The adults or nymphs of the pentatomid bug were kept under two different types of photoperiod; long-day condition (16: 8-hr light-dark, 16L8D) or short-day condition (8: 16-hr light-dark, 8L16D). It became clear that, in order to obtain fertile female of A. spinidens, long-day condition at the nymph stage was indispensable, as well as long-day condition of the adult stage. In addition, the fertile female incidence increased when the long-day exposure period in nymph stage was lengthened. It was identified the diapause of A. spinidens was induced by short-day during the adult stage or short-day during the entire period of nymph stage under 25°C.