What we really have to understand is how they accomplish all of that. One factor that makes spiders so important to the natural world is that spiders have the ability to build their own webs. Whether or not they’re able to build webs on some species of arachnids is not yet entirely understood, but we do know that different species build theirs differently. Many spiders build webs about 15-20 times the diameter of their body, whereas more typical arthropods (like crabs) may only need to be about 1/10th the size in order to build their webs. The big difference is that spiders’ webs are made from silk that covers their bodies and as they spin them, they capture insects to eat. And they are so efficient at doing so that webs can cover a wide range of habitats, including the bottom of ponds and underneath leaves, making them perfect for trapping insects.