Spiders, as predators of insects and other invertebrates, are an important part of the natural enemies, and they are recognized as an important biological control agent. Plutellaxylostella (Linnaeus, 1758), the diamondback moth (DBM), is a well-known and destructive insect pest of brassicaceous crops worldwide. Here, we analyzed the functional responses of four spiders (Araneae) – Ebrechtellatricuspidata (Fabricius, 1775) (Thomisidae), Pardosalaura (Karsch, 1879) (Lycosidae), Pardosaastrigera (Koch, 1878) (Lycosidae), and Pardosapseudoannulata (Bösenberg & Strand, 1906) (Lycosidae) – on P.xylostella larvae. We also analyzed intraspecific disturbances in the predation reaction and the intensity of scrambling competition of the spiders to P.xylostella larvae. Our results demonstrated that the functional responses of four spiders of different genera were in line with the Holling II model. Two Lycosidae spiders (P.astrigera and P.pseudoannulata) had the potential to control P.xylostella, and female and male spiders that belonged to the same species had different functional responses to P.xylostella. The functional responses of female predation of P.astrigena, P.laura, and P.pseudoannulata was stronger than the males, but male E.tricuspidatus had stronger functional responses to predation than females. We used the Hassell model to describe the intraspecific disturbance experiments of four spiders. There were intraspecific disturbances in the predation reactions of spiders, indicating that the predation ratio of spiders decreased in relation to the increase of its density, and with the increase of spider density, the intensity of scrambling competition of the spider increased.
Seasonal prevalence of natural enemies of the diamondback moth, Plutella xylostella L. in Kagoshima Prefecture.
