Using Haplogonatopus atratus, a solitary parasitoid of the small brown planthopper,Laodelphax striatellus, we traced the development of the first- and second-laid eggs from oviposition to adult emergence, and revealed their survival rates, developmental periods, and adult head widths in self and conspecific superparasitism. When the interval between the first and second ovipositions was 1 h, the survival rate of the second comer was as high as the survival rate of the immature parasitoid in singly-parasitized hosts (60%), but the survival rate of the first was less than 20%. With increasing oviposition interval, the survival rate of the second decreased while that of the first increased. Consequently the survival rate of the first comer became similar to, or more than, that of the second for oviposition intervals of 1 day and over. For almost all intervals the survival rate of the first comer and that of the second were each higher in conspecific superparasitism than in self superparasitism. As a result, in conspecific superparasitism, the sum of survival rates of the first and second comers was higher than the survival rate of the parasitoid in single parasitism for most oviposition intervals; on the other hand, in self superparasitism the sum was similar to or less than the survival rate in single parasitism. The developmental period for wasps from superparasitized hosts was similar to that for wasps from singly-parasitized hosts both when superparasitism was self and conspecific. However, the developmental period of the second comer was longer than that of the first for 8- and 12-h intervals, while the reverse was true for almost all of the other intervals. As for the head width of emerged wasps, there was no difference between wasps from superparasitized hosts and wasps from singly-parasitized hosts for almost all oviposition intervals. The head width of the second comer, however, was larger than that of the first for oviposition intervals of not more than 48 h in both self and conspecific superparasitism.