抄録
Effects of fenobucarb, a methylcarbarnatc insecticide, on several species of aquatic insects were investigated using indoor model streams. Concentrations of fenobucarb residues in the water of the model streams were 78-85 % of its nominal level until 24 h, except at low concentrations (less than 20 μg1-1) in the water. The LC50 values of fenobucarb for the larvae of Ephemeroptera, Epeorus latifolium, Ecdyonurus yoshidae and Baetis thermicus were low (2-17 μg1-1). Their predators, the larvae of Oyamia gibba and Protohermes grandis, were less sensitive (48-h LC50 values,42 and >160 μg1-1, respectively)than the Ephemeroptera to fenobucarb. LC50 values among the Ephemeroptera larvae were considered to be significantly different since their 95% confidence limits did not overlap. The larvae of Isonychia japonica and E.yoshidae were more sensitive to fertobucarb in their earlier stages (at head capsule widths of <1.0 mm and <1.6 mm, respectively). On the other hand, the larvae of E. lattfolium seemed to differ considerably in their sensitivity to a low concentration (10 μg1-1) of fenobucarb.
