Insecticide susceptibility of three spiders in paddy field.

Insecticide susceptibilties of the first instar nymphs of three spiders, a wolf spider (Pardosa pseudoannulata) and two dwarf spiders (Ummeliata insecticeps and Gnathonarium exsiccatum), inhabiting paddy fields were examined by the dipping method against five insecticides, diazinon, phenthoate, BPMC, cardaryl and etofenprox. The three spiders were most susceptible to etofenprox. Pardosa pseudoannulata was rather susceptible to phenthoate and carbaryl. The other insecticides did not have high toxic activity to the three spiders. The LC 50 of the insecticides tested except for etofenprox to P. psuedoannulata was 4 to 47 times greater than that for the ofher two spiders. The susceptibility to etofenprox was compared between the first instar nymphs and the female adults of G. exsiccatum. The LC 50 value for adults was 35 times greater than that for the first instar.