To understand the oviposition biology of arrowhead scale, Unaspis yanonensis (Kuwana) (Homoptera: Diaspididae), the longevity and fecundity of the overwintered females were examined at various temperatures (16, 20, 24, 28, and 32℃). The total fecundity increased with rising temperature, showed a maximum of 260.9 crawlers per female at 24℃, and then declined thereafter. Females showed a periodical oviposition activity. The 1st cycle fecundity was identified at all temperatures examined, and was not significantly different between 16 and 28℃. However, the 2nd cycle fecundity and later cycle fecundity were much lower at 16, 20, and 32℃ than those at 24 and 28℃. The pre-oviposition period ranged from 49.0 d at 16℃ to 19.7 d at 32℃, and was the shortest 19.4d at 28℃. The linear lines of mean development rates (1/mean pre-oviposition period) against temperatures provided the estimate of low-threshold temperature 8.7℃ for pre-oviposition stage and the thermal constant of 358.1 DD. The lower threshold temperature and thermal constant for the completion of U. yanonensis pre-oviposition period well predicted the first crawler occurrences in the fields.