The fecundity of summer generation adults of arrowhead scale, Unaspis yanonensis (Kuwana) (Hemiptera: Diaspididae), was examined at constant temperatures. The total fecundity increased up to $29^{circ}C$ and declined thereafter. Total fecundity reached a maximum of 254.5 eggs (crawlers) per female at $29^{circ}C$. Females showed periodic oviposition activity but the pattern differed with temperature. Three or more oviposition cycles were occurred at 25 and $29^{circ}C$. At the other temperatures, the 2nd oviposition cycle was reduced or obscure. And oviposition cycle after the 2nd cycle was not obvious at low or high temperatures. The fecundity of the 1st cycle was significantly different according to temperature, showing higher fecundity at 25 and $29^{circ}C$. Fecundity after 1st cycle at 13, 17 and $21^{circ}C$ were lower than at 25 and $29^{circ}C$. The sex ratios of hatched nymphs in terms of female : male in 13, 17, 25, 29 and $33^{circ}C$ were 1 : 0.48, 1 : 4.79, 1 : 2.48, 1 : 1.85 and 1 : 0.56, respectively.