Effects of background pattern on insect perception of webs spun by orb-weaving spiders

Abstract

Recent studies show that many insects are able to see spider webs and avoid them. The orbspinning spiders and their close relatives are an abundant and diverse group of predators that make use of a variety of habitats and light environments. A combination of field and laboratory approaches was used to explore the effects of light environment, silk reflectance and background pattern on insect perception of spider webs. Field experiments showed that in dim visual habitats, background patterns have no significant effect on insect perception of webs but in bright visual habitats, patterns behind webs decreased the ability of insects to see and avoid them. In the laboratory Drosophila melanogaster Meigen have more difficulty seeing brightly lit webs when they are suspended close to backgrounds of high spatial frequencies than when webs are suspended in front of distant backgrounds or of low spatial frequencies. When Drosophila are confronted with webs characterized by low reflectivity, however, they are unable to see and avoid them, regardless of light level or background spatial pattern. Web visibility results from a series of complex interactions among the reflectance properties of silks, web architecture, background pattern, ambient light level and the peculiar visual physiology of the approaching insect.