Some people love them and some people hate, or even fear them, but spiders are a part of the world around us. Like it or not, we have to live with them.
Spiders are a kind of arachnid, a group of arthropods that also includes mites, ticks and scorpions. All spiders and arachnids have eight legs, and almost all of them have eight eyes. Beyond these similarities, there's a lot of variation among the approximately 50,000 spider species on Earth.
That's right. The world is home to about 50,000 different kinds of spiders. They live in almost every type of habitat — forests, deserts and even our own homes. There are even spiders that live on water and underneath water. While it may seem like there are plenty of spiders to go around, some species are endangered, affected by habitat loss and invasive species that dominate their habitats.
Read on to learn more about what makes spiders special.
Almost all spiders are venomous, but almost none can hurt you
We're going to level with you: The vast majority of the world's spiders are venomous. But before you let that shape your opinion of them, you should know that's just half the story. Here's the rest: Of the 50,000 known spider species in the world, only 25 have venom that can cause harm to humans. That's just 1/20 of 1% of spiders that are dangerous to humans.
Words to know
Arthropod: Invertebrate animals having an exoskeleton, a segmented body and paired jointed appendages. This group of animals includes insects, spiders and crustaceans.
Carnivore: An animal that eats the flesh of other animals.
Chelicerae: Claw-like appendages on the front of the mouth of spiders and other arachnids and arthropods.
Mandible: A jaw or jawbone.
Venomous: Capable of injecting venom by bite or sting.
And one last thing: Spiders don't really want to bite you. We aren't part of their normal diet, so they only bite people as a last resort.
In the United States, dying from a spider bite is extremely rare. There are less than three deaths per year because of spider bites. In Illinois, the only spiders that can cause harm to humans are brown recluse and black widow spiders.
They can't chew
Almost all spiders are carnivores, so it may come as a surprise to learn that they can't chew, at least not like we do. Unlike mammals and most insects, spiders do not have mandibles that aid in biting and chewing. Instead, they have chelicerae, which are external structures that work similar to a jaw. Spiders use their chelicerae to hold prey in place while they inject it with venom.
Instead of chewing their food, spiders will first "spit" enzymes either on or in their prey. This will liquify it. Then they eat the prey by sucking in the juices.
They all make silk, but they don't all make webs
All spiders make silk — it's one of the things that makes a spider a spider. However, not all spiders make webs. A spider web is technically any structure made of silk that is used to catch prey. About half of all known spider species catch prey with silky webs.
Among spiders that don't make webs, silk is used in many different ways. Some spiders build nests and cocoons from their silk, and some use silk strands to wrap up their prey. Silk strands can also be used as drop lines or anchor lines, trailing behind them as they move about. Spiders even sometimes eat their silk and use it to make new silk.
They can be very big and very small
When you think about the biggest spiders you've seen, wolf spiders may come to find. These spiders, which include hundreds of different species, can be between a half-inch to an inch or two long, but they aren't even close to the biggest spiders in the world.
The title of world's largest spider could be awarded to two different species, depending on whether the crowning criteria is leg span or body mass. By leg span, the giant huntsman is the largest, with a leg span of as great as 12 inches. By weight, a tarantula species called the Goliath birdeater takes the cake, weighing in at 6 ounces. Don't worry. You're unlikely to encounter either of these spider species. The giant huntsman lives in Laos in Asia, and the Goliath birdeater lives in rainforests in South America.
The title of world's smallest spider is contested too. The Patu digua, which is native to Colombia, is often said to be the world's smallest spider, with a body that's only 0.015 inches long. That’s easily small enough to fit on the head of a pin. But another species, the Anapistula caecula of West Africa, is thought to be even smaller. The females of the species measure just slightly larger than the male Patu diguas, and female spiders are almost always larger than males. It's never been proven that male Anapistula caeculas are smaller because they've never been seen or photographed.
There's a day dedicated to saving them
National Save A Spider Day, celebrated each year on March 14, certainly isn't on par with holidays like Thanksgiving and Halloween, but raising awareness about the importance of spiders is as good a reason for a holiday as any.
The festivities on National Save A Spider Day are low key as holidays go. It's a good time to step a little more carefully and try to tolerate any eight-legged creatures you come across. Really, though, if you can be convinced to save a spider on March 14, you can — and should — do it every day.
Need convincing? Spiders actually play an important role in the ecosystem, primarily as predators of insects. Their hunting of these insects helps keep their populations in check and food chains in balance.
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