http://clicklancashire.com/2017/03/17/worlds-spiders-eat-more-animals-than-all-humans-put-together.html

World’s spiders eat more animals than all humans put together

You might be surprised to know that about 27 million tons of spiders, consume anywhere between 440 million and 880 million tons of insects each year.

The jumping spider Phidippus apacheanus feeding on a red-banded leafhopper (Graphocephala coccinea). Spiders in these locations catch enormous numbers of forest and grassland pests, while spiders living in deserts, Arctic tundra and agricultural areas kill fewer insects.

In the first analysis of its kind, researchers used data from 65 previous studies to estimate that a total of 25 million metric tonnes of spiders exist on Earth.

But it’s not all good for spiders – sometimes, they end up on the wrong side of the food chain. Our stomachs are pretty big, but compared to the humble spider, that’s basically nothing.

The second method used published data on the annual prey kill per square meter of spider communities in different biomes. The wide range of the 400-800 million metric tons estimate shows just how much extrapolation went into this and how hard it is to land at a more exact number.

That’s the same amount of meat and fish that humans eat over twelve months.

So how exactly does one calculate how much arachnids eat annually?

When you factor in other food sources such as grains, vegetables, and dairy, humans still consume far more than spiders: According to the UN’s Food and Agriculture Organization, people ate more than 1 billion tons of cereals alone in 2007.

However, for desert spiders, which have evolved to survive under hard circumstances, the number stands between 0.01 and 0.04 milligrams of food per milligram of a spider.

Again, their estimates suggest that all spiders eat 400 to 800 million tons of insects, pests and other prey each year. Greater than 90 percent of that prey is insects and springtails (Collembola).

Most of are insects but the largest tropical species of vertebrates such as frogs, lizards, fish and small mammals. “They serve as food for thousands of arthropod-eating animals – an estimated 8,000-10,000 specialized insect species and many passerine birds (an estimated 3,000-5,000 species) feed on spiders“. In these environments, Stephanie Pappas of Live Science explains, spiders do not have to contend with human activity that disrupts their habitats. A British scientist speculated in 1947 that there were about 2.2 trillion spiders – in England and Wales alone, Nyffeler told LiveScience.