Web-site selection strategies of linyphiid spiders in alfalfa: implications for biological control |
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Authors: | James D Harwood John J Obrycki |
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Institution: | (1) Department of Entomology, University of Kentucky, S-225 Agricultural Science Center North, Lexington, KY 40546-0091, USA |
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Abstract: | Site-specific foraging can enhance the ability of generalist predators to provide effective and sustainable levels of pest
control in agroecosystems. This can result from increased growth rates, higher population densities, and improved capture
frequencies of pests at high prey density microsites. We tested the hypothesis that linyphiid spiders would exhibit microhabitat-specific
web-site selection strategies in alfalfa. This was predicted to result in high prey densities at web-sites compared to paired
non-web-sites through direct, or indirect, selection of prey-rich habitats. A total of 22,242 potential prey items were collected
from mini-sticky traps located at 896 microsites. Web-centered mini-sticky traps on the ground, representative of Erigone autumnalis Emerton (Araneae: Linyphiidae) webs, captured similar numbers of potential prey as paired non-web-centered traps nearby.
However, aerial sticky traps at web-sites of Bathyphantes pallidus (Banks) (Araneae: Linyphiidae) contained significantly more Diptera and Empoasca fabae (Harris) (Homoptera: Cicadellidae) than paired non-web-centered sticky-traps. Prey activity-densities also varied between
web-sites of E. autumnalis and B. pallidus. Diptera were dominant at aerial microsites of B. pallidus whilst Collembola were abundant on ground-based traps of E. autumnalis. These results suggest that in alfalfa, the pressure for selecting prey-rich web-sites by erigonine spiders is low, but B. pallidus exhibits a selective web-location strategy targeted towards high quality dipteran prey. These sites also captured large numbers
of E. fabae, a major pest of alfalfa, thus implicating aerial-based linyphiines as valuable predators in biological control. |
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Keywords: | Alternative prey Araneae Collembola Empoasca fabae Food webs Generalist predators Linyphiidae Microsite selection Predator– prey interactions |
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