Invertebrates
Spiders are some of the most incredible animals on the planet! These eight-legged creatures make silk that is stronger than steel, catch their dinner in sticky webs, and can be found on every continent except Antarctica. But spiders are not scary-they are fascinating! Jumping spiders have adorable fuzzy faces and can leap 50 times their own body length. Peacock spiders dance with colorful flaps to impress their mates. Most spiders are harmless to people and actually help us by eating mosquitoes and other pesky bugs. Let's explore the amazing world of spiders!
Spiders have eight legs-that is the easiest way to tell them apart from insects, which have only six! A spider's body has two main parts: the cephalothorax (head and chest combined) and the abdomen (the round back part). Most spiders have eight eyes, though some have six or fewer. Despite all those eyes, most spiders cannot see very well! Jumping spiders are the exception-their big front eyes give them amazingly sharp vision!
Spiders come in an incredible variety of sizes and colors! The Goliath birdeater tarantula is the world's largest spider, with legs spanning 12 inches-as wide as a dinner plate! The smallest spiders are tiny Patu digua spiders, smaller than the period at the end of this sentence. Spiders can be brown, black, yellow, red, green, or even bright blue. Peacock spiders have colorful flaps that they raise and shake during dances to attract mates!
All spiders have special body parts for making silk! At the back of a spider's abdomen are organs called spinnerets that produce silk. Spider silk is incredibly strong-pound for pound, it is stronger than steel and tougher than Kevlar! Different types of silk are used for different jobs. Sticky silk catches prey. Strong dragline silk supports the web's frame. Soft silk wraps up captured insects. Some spiders can make seven different types of silk!
Spiders live almost everywhere on Earth! They are found in forests, deserts, grasslands, caves, mountains, and even your house! The Himalayan jumping spider has been found at over 22,000 feet above sea level-making it one of the highest-living animals in the world. Diving bell spiders live underwater, creating air-filled silk bubbles to breathe in! Some spiders live in the hottest deserts, while others survive freezing Arctic temperatures!
Different spiders choose different homes! Orb weavers build beautiful round webs between branches to catch flying insects. Trapdoor spiders dig burrows with silk-lined doors that flip open to grab passing prey. Funnel-web spiders build sheet-like webs with a tunnel to hide in. Crab spiders sit inside flowers, perfectly camouflaged, waiting for bees and butterflies to land. Social spiders live in huge communal webs with thousands of roommates!
Many spiders are expert travelers! Young spiders use a trick called "ballooning" to travel long distances. They climb to a high point, release a strand of silk, and let the wind carry them like tiny kites! Baby spiders have been found flying at altitudes of over 16,000 feet, and they have been collected on ships far out at sea. This is how spiders spread to new areas-even to islands hundreds of miles from the nearest land!
Most spiders eat insects and other small creatures! Web-building spiders trap flies, mosquitoes, moths, and beetles in their sticky webs. When an insect gets stuck, the spider feels the vibrations through the silk, rushes over, and wraps the prey in silk. Spiders cannot chew-they inject digestive juices into their prey that turn the insides to liquid, then they drink it like a bug smoothie!
Not all spiders use webs to catch food! Jumping spiders are active hunters that stalk and pounce on their prey like tiny cats. Wolf spiders chase insects across the ground at high speed. Bolas spiders swing a sticky ball on a silk thread to catch moths like a tiny cowboy with a lasso! Fishing spiders sit on the surface of ponds and catch small fish and tadpoles. Net-casting spiders hold a stretchy silk net and throw it over passing insects!
Some spiders catch surprisingly large prey! The Goliath birdeater tarantula can eat mice, lizards, frogs, and small birds! Golden silk orb weavers make webs strong enough to catch small birds and bats. Fishing spiders catch fish twice their own size. However, most spiders are helpful to people because they eat huge numbers of pest insects. Scientists estimate that the world's spiders eat 400 to 800 million tons of insects each year!
Mother spiders lay their eggs in silk egg sacs! Each sac can contain hundreds of tiny eggs. Some spiders make round egg sacs that they hide in safe spots. Wolf spiders carry their egg sacs attached to their spinnerets wherever they go. Garden spiders attach their large, papery egg sacs to plants. A single spider can lay over 1,000 eggs in her lifetime!
Baby spiders are called spiderlings, and many mothers protect their young! Wolf spider babies climb onto their mother's back after hatching and ride around for a week or more-sometimes over 100 babies at once! Nursery web spiders build special tents of silk where their babies can safely grow. Some mother spiders feed their babies by catching prey and sharing it. A few species even let their babies eat them after they hatch!
Spiderlings are surprisingly independent! Most baby spiders are on their own soon after hatching. They use ballooning to fly to new locations on silk parachutes. Young spiders build tiny webs and catch small insects right away. As they grow, they must shed their exoskeleton (called molting) multiple times. Each time they molt, they emerge a little bigger. Most spiders molt 5 to 10 times before reaching full size!
Spider lifespans vary greatly by species! Most small spiders live only 1 to 2 years. Wolf spiders can live 3 to 4 years. Female tarantulas are the longest-lived spiders-some can live over 25 years in captivity! Male spiders usually live shorter lives than females. Some tiny spiders complete their entire life cycle in just a few months. The larger the spider, the longer it usually lives!
Spiders are nature's best pest controllers! They eat incredible numbers of insects that bother people and damage crops. Scientists estimate that spiders eat 400 to 800 million tons of insects every year-more than the weight of all the humans on Earth! Without spiders, we would be buried in mosquitoes, flies, and crop-eating bugs. A single garden spider can eat over 2,000 insects in its lifetime!
Spiders are an important food source for many other animals! Birds, lizards, frogs, wasps, and other spiders all eat spiders. In many ecosystems, spiders are a key link in the food chain. Baby birds in particular depend on spiders as a high-protein food during their first weeks of life. By supporting large populations of spiders, we help support all the animals that depend on them!
Spider silk inspires scientists and engineers! Researchers are studying spider silk to create new super-strong materials. Spider venom is being studied for possible medical breakthroughs, including treatments for heart conditions and brain injuries. Some spider venoms contain compounds that could lead to safer pesticides. These eight-legged creatures may hold the key to amazing discoveries!
Spiders deserve our appreciation, not our fear! Most spiders are completely harmless to people. Of the 50,000 known species, fewer than 30 have venom that can cause problems for humans. Spiders do not want to bite people-they bite only when they feel trapped or threatened. By leaving spiders alone in your garden and learning about them, you help one of nature's most important pest controllers do its job!