Spiders Eat Hundreds of Millions of TONS of Bugs Every Year

Jurgen Otto via Wikimedia Commons // CC BY-SA 2.0
Jurgen Otto via Wikimedia Commons // CC BY-SA 2.0 / Jurgen Otto via Wikimedia Commons // CC BY-SA 2.0

Arachnophobes might cherish the idea of a world without spiders, but consider this: Without them, the planet would be covered in a thick, wriggling blanket of other bugs. Researchers writing in the journal The Science of Nature estimate that our spider friends gobble up 400 to 800 million tons of insects and other small prey every single year.

It’s a myth that you’re never more than 3 feet from a spider, and it’s a myth that we’re all constantly swallowing spiders in our sleep. But spiders are definitely plentiful; the authors of the new study calculated an average of 131 spiders per square meter of land. But we’re hardly talking about an even distribution here; most of those little creatures are concentrated in forests and fields.

Next, the scientists added up the mass of all the spiders on the planet, then used their eating habits to calculate the annual weight of their collective meals. The exact number is tricky to pin down, but the authors say it’s somewhere in the neighborhood of hundreds of millions of tons.

To put that in context: Human beings consume around 400 million tons of meat and fish per year. Relative to spiders, our bodies, and the bodies of our prey, are enormous. But the itsy-bitsy spiders are giving us a run for our money, eating at least that much meat in the form of bugs and very small vertebrates like lizards, birds, and mammals.

Or, put another way—imagine all the meat and fish you’ve eaten, say, this week. Now imagine that same space and weight occupied by bugs. Now imagine that those bugs are gone, because our spider neighbors took care of them.

As The Washington Post notes, if you added together all the adult humans on the planet, our biomass would only total 287 million tons, which means that "the global spider community," as the researchers call it, could theoretically digest all of us and have room left for dessert. But spiders don't want to eat people, and most of them couldn't even if they wanted to.

Spiders aren’t bad, nor are the bugs they eat—nor are the animals that eat spiders. We need them all to make this wonderful world of ours go round. So the next time you see a spider, maybe let it know you appreciate its hard work by leaving it be. We kind of owe them.