Research: Spiders feast on 400-800 million tons of insects every year

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Story highlights

  • Researchers calculate how many tons the world's spiders consume
  • Spiders are all carnivores and can be found in very inhospitable environments

(CNN)The next time you see a spider crawling around your house, look at the bright side. It's probably feasting on a bunch of other insects and providing you with free pest control.

A new study released on Tuesday says that spiders eat an estimated 400 to 800 million metric tons of insects every year.
For comparison, the entire human population consumes about 400 million tons of meat and fish every year.
    "Our estimates for spiders appear to be of the same order of magnitude as the prey kill by whales in the world's oceans which has been estimated to be in the range of 280-500 million tons annually," wrote the authors in The Science of Nature.
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    The eight-legged carnivores eat an astounding amount, highlighting their natural role in getting rid of pests and insects that transmit diseases or parasites.
    They also have uncanny survival mechanisms. Spiders have been found in the northern most islands of the Arctic, the hottest deserts, at the highest altitudes of any living organisms, bogs, sand dunes and other types of habitats. Essentially, they'll go wherever they can find food.
    "There is hardly any terrestrial area on this globe where spiders would be missing," wrote the researchers, Martin Nyffeler of the University of Basel and Klaus Birkhofer of Lund University in Sweden and the Brandenburg University of Technology Cottbus-Senftenberg in Germany.
    The researchers estimate that there's probably around 25 million metric tons of spiders in the world.
    They used two models to calculate how much prey spiders consume and the average number of spiders per square meter in a certain habitat.
    "Our estimates of the global annual prey kill imply that spiders exert considerable predation pressure on insect populations, especially in forests and grasslands," wrote Nyffeler and Birkhofer.