Susceptibility of wolf spider, Lycosa terrestris (Araneae: Lycosidae) to chlorpyrifos.

The present study was designed to check the effect of chlorpyrifos (Lorsban) on Lycosa terrestris, the most dominant ground spider in the agroecosystem of Punjab, Pakistan. For this purpose topical and residual bioassay tests were performed. Probate analysis showed that this insecticide is highly toxic for both sexes. The calculated LD50 values were less than field dose. Results of residual bioassays showed that this insecticide is highly toxic to spiders even after one month of its exposure. Negative effects of this insecticide not only reduces the biological control potential of L. terrestris but also poses a serious threat to other natural predators of agroecosystems.