Spider diversity and the impact of ecologically dominant species on insect pests of rice and wheat crops

Abstract

1. Spiders are an abundant and species-rich taxon of generalist predators that can affect herbivore populations and ecosystem functioning in agroecosystems. The present study was focused on the diversity and abundance of agroecosystem-inhabiting spiders and their impact on insect pests of rice and wheat crops. The crop fields were visited weekly to record spider diversity by the all-out search, sweep net and the pitfall trap methods.
2. Fourteen species of spiders and six species of insect herbivores were recorded in the rice and wheat cropping systems. The lynx spider, Oxyopes javanus and the web-making, Neoscona theisi and Tetragnatha javana were the ecologically dominant, arboreal species, while Pardosa sumatrana, an epigeal lycosid spider, was the dominant, ground-dwelling species, in both cropping systems.
3. Furthermore, to highlight the impact of these four ecologically dominant species of spiders on insect pests of crops, We propose estimates of the biomass of annually killed insect pests. In the event of an anticipated abundant prey availability, the annual prey kills of these four spider species were estimated to be in the range of »3-8 kg (fresh weight) over the entire cultivated field (Area= 65 ha).
4. The assessment of the estimated annual insect pests kill and the comparative impact of spider predation in the annual agroecosystems will help in expanding the approach of conservation biological control.