Although the larval habitats of S. infuscatum are paddy fields, all adults leave the paddy fields for forest gaps after emergence, and remain there during their sexually immature stages. In late summer when they have matured, some visit the paddy fields in tandem flight for oviposition. However, many 9 9 remain perching in the forest gaps, where no mating behaviour is observed. To evaluate the habitat selection of S. infuscatum 9 9 in the forest gaps, fecundity was examined by means of dissection. In the morning, the 9 9 remaining in the forest gaps loaded fewer mature eggs (ca 100) than did ovipositing 9 9 in the paddy fields (ca 300). 9 9 remaining in the forest gaps throughout the day were not willing to visit the paddy fields for oviposition due to the low egg number loaded. This could be because these 9 9 were developing their eggs, having loaded more sub-mature eggs (ca 60) than ovipositing females in the paddy fields (ca 30). As a result, in the evening, 9 9 that had developed nearly 500 eggs appeared. In an artificial oviposition experiment, the 9 9 in the paddy fields released their eggs significantly faster (60 eggs/min) than did those in the forest gaps (16 eggs/min), and released almost all of their eggs, while the 9 9 in the forest gaps retained a considerable number of eggs in their ovaries. Although 9 9 loaded 400 ovarioles irrespective of their age, the number of immature eggs per ovariole decreased with age. Consequently, a 9 might have laid more than 2000 eggs in her life span. 9 9 must visit the paddy fields cyclically several times in a single month and stay in the forest gaps during the other days.