Age-specific fecundity, survival rate and proportion of the sterile females in the population of Nezara viridula that belongs to the first and the second generations were studied in field cages. Larvae of the fifth instar were kept in each cage and examined at 3 day intervals. Every newly emerged adult was marked to obtain an individual record of life span and mating behaviour. Eggs deposited in the cage were thoroughly examined at each survey and eradicated after taking count. Relation between mating frequency and egg laying obtained from the daily examination of 15 pairs of the first and 27 pairs of the second generation in the laboratory was used for the estimate of the fraction of sterile females in the field cages. Longevity of adults in the field cages was 18.7±14.2 days among males and 27.5±19.2 among females, on the other hand 36.6±10.9 and 45.4±12.2, respectively in the laboratory. The survivorship curves of the cage populations are characterized by rather a concave type or a steep fall at the early period of adult life. After passing this period, adults die almost at a constant rate until about 60% death of the total population results and the rate suddenly increases along with the aging of adults.<br>There is a great variation in sexual activity among individuals of both sexes. And about half or more adults of both sexes could not be observed during mating. As mating behaviour of females is closely related to egg laying, the fraction of sterile females among those non-mating individuals was estimated from the percentage sterility obtained in the laboratory populations in regard to the mating frequency. It was calculated that a total of 43% of the females had died without reproduction, 33% of which was ascribed to the death in the preoviposition period and 10% was considered to be sterile showing no apparent difference from normal ones. In addition to this, it is suggested that there are males that are sexually weak or impotent in much the same proportion as females.<br>It is postulated that the low fecundity accompanied by high density should not be interpreted simply as a shift of mean fecundity per female, but such a shift of mean is attributable to a decrease in mean fecundity per reproducing feamale on one hand, and to an increase in proportion of sterile females in the pertinent population on the other. Using the values of mortality obtained from life tables, net reproduction rate (Ro) was calculated and gave the values of 0.4 and 2.4 for the first and the second generations, respectively. Therefore, the decrease in the population of the first generation is compensated by the increasing trend in the second generation which develops principally in the paddy fields of early planting rice. When the mortality of immature stages is 97.57%, the value of Ro becomes unity. Values of intrinsic rate of natural increase (r) of the southern green stink bug were shown in Table 6 with varying degree of mortality and duration of immature stages.