The Effect of Light and Prey on Web Placement in Agelenopsis spp.

Presenter

Wes Walsh

Campus

UMass Amherst

Sponsor

Elizabeth Jakob, Department of Biology, UMass Amherst

Schedule

Session 4, 2:30 PM - 3:15 PM [Schedule by Time][Poster Grid for Time/Location]

Location

Poster Board A13, Campus Center Auditorium, Row 1 (A1-A20) [Poster Location Map]

Abstract

Light pollution is a widespread sensory pollutant contributing to insect declines; an estimated one-third of insects attracted to stationary light sources will die from either exhaustion or predation by sunrise. Many insectivorous vertebrates hunt near artificial light to catch more prey, but few studies have examined whether invertebrate predators similarly exploit artificial light. Here I test how artificial light and prey affect web placement in Agelenopsis spp., a common urban spider. I kept spiders in enclosures with a lightbulb outside one corner. Lightbulbs either stayed on (light) or off (control) all night, and I compared the distance from the spider’s web to the lightbulb corner between groups. I then repeated this experiment but added prey in the corner opposite the lightbulbs and compared the distances from the spider’s web to the light and to the prey between groups. In the absence of prey, light treatment spiders made their webs significantly closer to the light compared to control spiders. When prey was present, light treatment spiders still made their webs significantly closer to the light and farther from the prey. Control spiders' webs were closer to the prey. This suggests Agelenopsis prefer to make their webs near light, even prioritizing it over prey. Outdoors, this likely draws them to prey-dense, artificially lit areas. Some urban insects, however, have reportedly evolved reduced flight-to-light behavior. Artificial light could therefore become an ecological trap for spiders if fewer insects approach light but spiders continue to forgo prey to build webs in the light.

Keywords

light pollution, insect predation, urbanization, Agelenidae

Research Area

Animal Behaviour

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