AbstractFemales of three skimmers, Orthetrum japonicum, O. albistylum and O. triangulare, were captured in forests and paddy fields. They were dissected and examined for the number of submature and mature eggs. Orthetrum japonicum and O. albistylum continuously developed eggs throughout their reproductive period. The volume of mature eggs in O. albistylum was the smallest among the three species. The number of mature eggs in ovaries decreased from morning to afternoon, suggesting that all of them oviposited around noon. The number of mature eggs laid by O. japonicum, O. albistylum and O. triangulare was estimated at about 400, 800 and >2000 a day, respectively.