Spiders exert a powerful negative pressure on insect populations. While this activity has been difficult to document, recent studies have consistently shown that spiders are important components of agricultural systems (Young & Edwards 1990, Nyffeler & Benz 1987, Riechert & Lockley 1984, Riechert & Bishop 1990, Mansour et al.1983). For a summary of the research to date see Wise (1993). Some spiders are able to identify insect eggs as food items (Richman et al. 1980) and thus may serve as important predators on this stage. It seems likely that, from an economic standpoint, spiders do more good than harm, even when venomous spiders are taken into account.
Literature Cited
Mansour, F., D. B. Richman, and W. H. Whitcomb. 1983. Spider management in agroecosystems: Habitat manipulation. Environ. Manage. 7:43-49.
Nyffeler M. and G. Benz. 1987. Spiders in natural pest control: A review. J. Applied Entomol. 104:190-197.
Richman, D. B., R. C. Hemenway, and W. H. Whitcomb. 1980. Field cage evaluation of predators of the soybean looper, Pseudoplusia includens. (Lepidoptera: Noctuidae). Envoron. Entomol. 9:315-317.
Riechert, S. E. and L. Bishop. 1990. Prey control by an assemblage of generalist predators: Spiders in garden test systems. Ecology 71(4):1441-1450.
Riechert, S. E. and T. Lockley. 1984. Spiders as biological control agents. Ann. Rev. Entomol. 29: 299-320.
Wise, D. H., 1993. Spiders in Ecological Webs. Cambridge University Press, Cambridge, UK.
Young, O. P., and G. B. Edwards. 1990. Spiders in the United States field crops and their potential effect on crop pests. J. Arachnol. 18: 1-27.
