Composition of spider communities in western Nebraska agroecosystems and their potential impact on two key pests of corn

As generalist predators, spiders are capable of fulfilling a variety of ecological niches allowing them to intercept and prey upon an array of insects. This characteristic could be particularly advantageous within agricultural ecosystems. This study sought to describe the composition and abundance of spider communities within western Nebraska corn fields, and to determine the potential for spider predation upon western corn rootworm (Diabrotica virgifera virgifera), a key pest of corn. Spiders were collected from corn fields in western Nebraska from May to August 2017 and 2018. Additionally, the population of D. v. virgifera was sampled to determine pest abundance throughout the season. During the 2017 collection period, 662 spiders were collected represented primarily by the following families: Lycosidae (53%); Linyphiidae (29%); Thomisidae (5%); Gnaphosidae (4%). In 2018, 324 spiders were collected representing a complex of families similar to those collected in 2017: Lycosidae (70%); Linyphiidae (17%); Gnaphosidae (5%); Thomisidae (2%). The lycosid community specifically was comprised of 21 species within 9 genera for both years combined, with Schizocosa ocreata and Schizocosa avida representing 66% and 15% of all lycosid species collected, respectively.  Pest population sampling confirmed the presence of D. v. virgifera in the sampled fields. Molecular gut content analysis of Lycosidae determined that predation of D. v. virgifera occurred with 16% (2017) and 24% (2018) of specimens tested positive for D. v. virgifera DNA. These results reveal the role of spiders within agroecosystems and can be utilized to develop improved conservation biological control programs in the future.