Ecology of spiders (Araneae) in a peanut agroecosystem

Spider populations were studied in three peanut fields in the Texas West Cross-Timbers region during the 1981 and 1982 growing seasons. Hunting species made up 85.8 and 91.7% of the spider fauna during 1981 and 1982, respectively; the remainder were web-builders. Three hunting families, Oxyopidae, Lycosidae, and Thomisidae, were dominant, constituting 74.6% of the total spider fauna for the two study years. Each family in turn was dominated by a single species. Oxyopes salticus Hentz (Oxyopidae) constituted 37.3% of the total spider fauna in 1982 and 16.2% in 1981. The Lycosidae were dominated by Pardosa pauxilla Montgomery and, as a family, were 31.0% of the fauna in 1981 and 26.6% in 1982. The Tomisidae were dominated by the Misumenops spp., mostly M. celer (Hentz). The Misumenops spp. were 14.0% and 14.1% of the spider fauna in 1981 and 1982, respectively. Spider abundance generally increased as the growing season progressed and plant size and structure increased. Lycosids were dependent on a closed plant canopy and were most successful in irrigated fields. Populations of most species, especially lycosids, declined in drought-stressed rain-fed fields, except Misumenops spp., which were most successful under rain-fed conditions. Ballooning activity of spiders was determined from suction trap samples in 1982; results showed O. salticus to be the most numerous aeronaut. The Araneidae and Linyphiidae were next most abundant in suction trap collections, although these and other web-building species constituted only 11.3% of the peanut spider fauna for the two study years. Identification of spider prey revealed a preference for Hemiptera (32.7%), with Lepidoptera and other Araneae constituting 17.3% each. Pest species taken as prey included Heliothis spp., Stegasta bosqueella (Chambers), leafhoppers, and thrips (Frankliniella spp.). Entomophagous species constituted about one -half the spider diet.