Spider facts: what is a spider? | Animal Fact Files

There are a lot of spiders in the world. Like, more than 40,000 different species are all alive right now on our planet. They live in just about every type of habitat, from deserts to tundras and beaches to mountaintops, though they haven't taken to the skies or the deep sea. Some spiders, like the diving bell spider, may spend quite a bit of time underwater, and there are some that live in intertidal areas and spend high tide in air-filled silken hideaways. Silk is exceptionally important to all spider species. Most people associate spider silk with the orb weavers who create intricate webs to capture food. But some spiders don't build fancy webs, like grass spiders. And others don't use silk for food collection at all. In a spider's life, silk may play a role in reproduction, housing, and even movement. Spiders are some of the only animals that use silk throughout their entire lives. Living spiders can be found on every continent except Antarctica. And they even live in space, with some human assistance. All spiders naturally have eight legs, fangs that can usually inject venom, and spinnerets that produce silk. Their bodies are split into two parts, the cephalothorax and the abdomen, and their legs are powered by hydraulics. Basically, spiders don't have muscles in their legs for opening their legs wide, which is why spiders' legs curl up when they die. Some spiders may also appear to have more than eight legs. A spider's pedipalps, which are positioned in front of the spider's first pair of legs, can look leg-like. These function as smell and taste organs, kind of like an insect's antennae. Spiders don't have antennae, they have pedipalps instead. A spider's fangs protrude from mouth structures called chelicerae, which are positioned next to the pedipalps. These can be quite large, such as in wandering spiders, or nearly imperceptible. Of the tens of thousands of living spider species, only a few can actually kill a human. Generally speaking, spiders want to conserve their venom, and often when they bite defensively, it'll be a dry bite, meaning no venom is released into the wound. In fact, one of the most well-known deadly spiders, the black widow, showed approximately 1,800 recorded bites in America during the year 2013, and not a single person died from these bites. That's not to say spiders can't kill people, just that they have a reputation much larger than reality. The largest spiders alive today are tarantulas, with the biggest individuals reaching up to four inches in body length, as in, not including the legs. The smallest spiders may be less than a millimeter long and could fit on the head of a pin. Their prey ranges in size to match. Some spiders catch their meals in webs, others go out and actively hunt their prey. Some wait inside their homes and let the prey come to them, but just about every spider species is a predator. Currently, the only known exception to this rule is a jumping spider with an almost entirely herbivorous diet. Spiders may make meals out of insects, other spiders, frogs, snakes, and even small birds and mammals. In turn, spiders are eaten by birds, reptiles, small mammals, and other invertebrates. Lots of people kill spiders out of fear as well, but these animals are exceptionally beneficial for pest control. While plenty of people have a legitimate fear, it's generally good to coexist with these wonderful arachnids. Female spiders are almost always larger than males. It's believed this is the case so that females can produce more eggs in their large bodies and that males can more effectively travel to find females. Some male spiders travel on long strands of silk that are caught by the wind and anchored to faraway objects that would otherwise be unreachable. The smaller the male, the more effective this movement strategy. Spider eggs are usually laid in an egg sac, and the spiderlings that hatch will go through 4 to 12 molts before reaching adulthood. Some spiders may live less than a year, while others can reach more than a decade in age. For more facts on spiders, check out the links in the description. Thank you to Adam for today's request. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files.