But they’re actually among the best regulators of pests on Earth. They reduce populations of the really bad insects — flies, roaches and mosquitoes, who are vectors of deadly diseases.
Over 2,000 years ago, spiders were used in China for biological control. The global spider community — over 40,000 species — kills 600 million tons of prey each year, many of which are harmful to our agricultural world.
What makes them such good guardians of our ecosystems? It’s all about their diversity and the diversity of their prey. Web-weaving spiders trap insects in their silken snares. Some, like wolf spiders, pursue their prey on foot. Others are ambush predators, camouflaging themselves as flowers to attract insects, and then killing them with a fatal pounce.
Forest managers who are concerned with ecologically friendly ways of suppressing pests are now working to enhance spider populations. A recent study at the University of Maryland found a simple way to maximize the services spiders provide: Give tree-dwelling spiders a more diverse habitat in which they can pursue their prey.
Their studies found that having a large variety of tree species with different structural features such as tree height, crown cover and foliage density helps increase spider diversity. These researchers are now advising forest managers on how to create forests that appeal to a higher diversity of spiders.
Trees and spiders are intimately — and helpfully — connected with each other. So, when you see a sinister-seeming spider, instead of shooing it away, think, instead, about letting it pass. It just might be saving the tree you love.
