About 90% of their prey consists of springtails, insects, and other arthropods. In addition to eating insects, big, tropical spiders will also prey on small vertebrates like frogs and fish from time to time, or eat plants.
Spiders evolved from an arachnid ancestor during the Devonian period around 400 million years ago. And humans eat around 400 million metric tons of meat and fish annually.
"Our calculations let us quantify for the first time on a global scale that spiders are major natural enemies of insects".
But if you're now worrying that the world might be inherited by spiders, remember that in turn, they are a source of prey as well.
For context, the study points out that humans consume about 400m tonnes of meat and fish every year, while whales feed on 280-500 tonnes and seabirds about 70m tonnes of seafood.
Catch it and escort it safely outside so it can do its part in downing an estimated 400 to 800 million metric tons of prey each year. "Spiders make an essential contribution to maintaining the ecological balance of nature", Nyffeler said, USA Today reported. Most spiders reside in forests, grasslands, shrublands, croplands, and deserts.
With more than 45,000 species and a population density of up to 1,000 individuals per square metre, spiders are one of the world's most species-rich and widespread groups of predators, the researchers said.
The figure reflects the fact that forests, grasslands and savannas are less frequently disturbed than for instance agricultural or urban areas, and therefore allow for greater spider biomass.
"These estimates emphasize the important role that spider predation plays in semi-natural and natural habitats, as many economically important pests and disease vectors breed in those forest and grassland biomes", says lead author Martin Nyffeler.
More than 8,000 species of birds, other predators and parasites feed exclusively on spiders, said the researchers. The scientific journal The Science of Nature has published the results.