The study suggests spiders dwelling in forests and grasslands "account for more than 95 percent of the annual prey kill of the global spider community". Large tropical spiders also occasionally eat small vertebrates, frogs, lizards, fish, birds or bats. Sharks are even lagging behind because they devour "only" 280 to 500 million tons of biomass per year.
Dr Martin Nyffeler, the University of Basel scientist who led this study, was inspired by a 1958 book called The World of Spiders, in which a British arachnologist author William Bristowe speculated that the weight of insects killed each year by the British spider population exceeded the combined weight of the British human population.
In the first analysis of its kind, researchers used data from 65 previous studies to estimate that a total of 25m metric tonnes of spiders exist on Earth.
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 thus make an essential contribution to maintaining the ecological balance of nature".
Spiders, in turn, serve as an important prey population.
Most spiders, of which there are some 45,000 species, are found in forests, grasslands and shrublands, followed by croplands, deserts, urban areas and tundra areas.
Just repeating that in case you passed out or anything: there's about 25 million tonnes of spiders somewhere in the world outside your house, folks (although, to be fair, some are inside it too). These eight-legged creeps have a population density of up to 1,000 individuals per square meter.
"Many economically important pests and disease vectors breed in those forest and grassland biomes", added Nyffeler.
"We hope that these estimates and their magnitude will help alert public opinion and improve the overall appreciation of the role of spiders."".
More than 8,000 species of birds, other predators and parasites feed exclusively on spiders, said the researchers.
The findings were discussed in The Science of Nature journal.