Spiders avoid building webs near European fire ants, their natural predators, by sensing the chemicals they give off in the environment, Simon Fraser University researchers have found.
The findings, published recently in Royal Society Open Science, give us a peek inside the enduring struggle between spiders and ants, and could lead to the development of natural repellents for homeowners worried about unwanted eight-legged guests.
Many ants prey on spiders, suggesting that web-building spiders may avoid locations near ant colonies or frequented by foraging ants. The research team, led by SFU biological sciences PhD candidate Andreas Fischer, hypothesized that spiders instinctively know to avoid building webs in these danger areas by sensing chemical cues left behind by predatory ants.
Researchers tested the theory by exposing filter paper to several species of ants and placing it in a multi-chambered habitat of four different species of spiders. Filter papers without ant semiochemicals were put in another chamber to see which area the spiders would prefer.
They found that the chemical deposits of European fire ants specifically, which are known to be aggressive omnivorous scavengers and prey on many invertebrates, had a deterrent effect on all tested spider species. The spiders chose to stay in the chamber that had no chemical trace of ants nearby.
Given how much time and energy spiders put into building their webs, Fischer said it makes sense that spiders in the wild would pick locations that have fewer threats to their survival.
Meanwhile, people's fear of spiders has led to the development of many insecticides and other chemical products that claim to repel spiders. But most of them have proven largely ineffective because spiders are able to abandon their webs and rebuild elsewhere. Harnessing the natural chemicals given off by their natural predators could help create more effective repellents for homeowners. Researchers warn against using European fire ants, an invasive species, themselves as pest control.
The research team also included SFU professor Gerhard Gries, undergraduate student Tea Dong and University of Toronto's Yerin Lee.
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