Abstract: Experiments on the effect of photophase on daily oviposition and progeny sex ratio of Anastatus japonicus, an egg parasitoid of the lychee stink bug, were conducted in the laboratory of 25.1℃, 70-85% RH and 500 lux lighting in 1991. Five different light:dark regimes were used in the experiment viz. 0:24 (hr), 6:18, 12:12, 18:6 and 24:0. The result revealed no significant difference in the parasitoid\'s daily oviposition among the 5 photophase regimes, but in sex ratio of the progenies. The parasitoid could lay eggs normally even under continuous dark conditions, although most eggs were laid during 6:00-12:00 am in the treatment of 6L:18D, 12L:12D and 18L:6D. The highest female rate of the progeny was found when the parent wasps were cultured under 6 hr photophase and 18 hr darkness, followed by that under 0L:24D, 12L:12D and 18L:6D. Continuous lighting resulted in the lowest female rate. Progeny\'s sex ratio from the eggs laid during different times of a day was not significantly different.