Reproductive capacity of first-generation adults of the rice water weevil Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae) in Zhejiang, China

First-generation adults of the rice water weevil, Lissorhoptrus oryzophilus Kuschel were collected from Yueqing (28.1degreesN latitude, 120.9degreesE longitude), Zhejiang, China, during late June and mid-July and reared on rice plants (cultivar Shanyou 63) in the laboratory (28+/-1 degreesC, 16L:8D) to examine their reproductive capacity. On plants aged 16-22 days, adults from the field and collected in mid-July could reach oviposition onset more rapidly and deposit more eggs than those collected earlier. Adults that emerged in late June and early July displayed a greater tendency to become reproductive, compared with those which emerged in mid-July. However, each of these groups of adults, either field-collected or newly emerged, deposited only 3-14 eggs within 60 days of feeding. Reproductive capacity was greatly related to plant age, with plants aged below 20 days being most favorable; on plants aged over 20 days, reproductive development could take place, but little oviposition was observed. These results indicate that the reproductive capacity of first-generation adults in Zhejiang is dependent upon the time of adult emergence and post-emergence, as well as on the age of rice plants.