Spiders might be the most feared creatures of them all. But these arachnids do a world of good. Spiders eat between 400 and 800 million tonnes of insects and invertebrates every year. If you’re not a fan of pesky bugs like mosquitoes, I highly suggest you make friends with these eight-legged critters. They also play an important role in the diets of many bird species. Between 3,000 and 5,000 bird species rely on spiders to survive.