NO NEGATIVE SUBLETHAL EFFECTS OF 2 INSECTICIDES ON PREY CAPTURE AND DEVELOPMENT OF A SPIDER

Laboratory experiments were used to analyse the effect of two insectic ides, dimethoate and cypermethrin, on prey capture, feeding and rate o f development of the wolf spider Pardosa amentata. Though partly letha l doses (LD50 and LD10) were applied and a high proportion of survivin g spiders suffered paralysis for one to two days, which could be fatal under field conditions, no negative effects on other investigated bio logical characteristics (including development and predation rates) of the surviving individuals were observed. With very low doses of cyper methrin, killing rate and feeding of females in the period between the final moult and egg-sac deposition were increased compared to untreat ed controls. This is the first evidence of enhanced performance due to an insecticide in a spider. The possibility of insecticide stimulatio n of predator population recovery after eradication by spraying is dis cussed. (C) 1998 SCI.