Spiders belong to the order Araneae and are arachnids, not insects. If you want a quick answer to what spiders are, they are air-breathing arthropods with eight legs, fangs, and silk-making organs that help them hunt, build shelters, and protect their eggs.
Most spiders hunt using silk, venom, or speed, and their body plan makes them very different from insects.
You can find spiders in almost every land habitat on Earth. They come in many shapes, sizes, and behaviors.
Some spin classic webs, some stalk prey on the ground, and some live hidden in burrows or houses. Their anatomy, classification, and range of lifestyles make them fascinating animals.
How Scientists Classify Spiders
Spiders form a major group within the arachnids. They stand apart from insects because they have eight legs, no antennae, and two main body sections.
The World Spider Catalog tracks tens of thousands of named spider species across many types of spiders. Their diversity is huge.
Differences From Insects And Other Arachnids
Spiders are arthropods like insects, scorpions, mites, and ticks, but they are not insects. Instead of antennae and chewing jaws, spiders have chelicerae with fangs and use silk in unique ways.
Main Groups Within Araneae
The order Araneae includes the ancient group Mesothelae and the larger group Opisthothelae, which contains Mygalomorphae and Araneomorphae. Liphistiidae families belong near the most primitive line of spider evolution.
Most living spider species fall into the more modern groups.
Number Of Spider Species
By January 2026, taxonomists had recorded about 53,680 spider species in 139 families. Scientists continue to describe new species and revise classifications.
Spider Anatomy And How The Body Works
A spider’s body helps it sense, grab, and produce silk. The main parts work together so the animal can move fast and feed on liquid food.
Cephalothorax, Abdomen, And Pedicel
The cephalothorax holds the eyes, legs, mouthparts, and most of the nervous system. The abdomen contains many organs, and the narrow pedicel connects the two body regions.
Chelicerae, Fangs, And Pedipalps
The chelicerae sit near the mouth and usually end in fangs. Many spiders use the fangs to deliver venom, while the pedipalps help with sensing, handling prey, and mating.
Spinnerets, Spigots, And Silk Production
Spinnerets are the silk-making organs at the rear of the abdomen. Each spinneret has tiny spigots that release silk from silk glands.
A single spinneret or a set of spinnerets can produce different kinds of silk for webs, egg cases, draglines, and shelter.
Book Lungs, Claws, And Movement
Many spiders breathe with book lungs, and some also use tracheal tubes. Their legs end in claws, and they move with hydraulic pressure, which helps extend the legs when they run, climb, or pounce.
How Spiders Hunt, Build, And Reproduce
Spiders use different hunting styles, from web traps to fast chasing and ambush. Silk helps them find food, make egg sacs, and protect young.
Web-Building And Orb Web Designs
Many web-building spiders make cobwebs, funnel web structures, or orb webs. Orb-weavers build circular webs to stop flying insects, while grass spiders often build sheet-like webs with funnel retreats.
Active Hunters And Ambush Strategies
Hunting spiders do not wait in a web. Active hunters rely on speed, eyesight, or surprise.
A water spider, Argyroneta aquatica, even lives underwater. Other spiders stalk, leap, or hide until prey comes close.
Egg Sacs, Spiderlings, And Life Cycle
After mating, a female may produce an egg sac or several egg sacs, each holding many eggs. Young spiderlings hatch, then molt as they grow, moving through stages until they become adults.
Common Spider Groups And Species People Recognize
People often recognize spiders by their shape, size, web style, or behavior. Some groups are famous for their looks, while others stand out because they live near homes or have bites people worry about.
Jumping, Wolf, And Crab Spiders
Jumping spiders, including the zebra jumping spider and many peacock spiders in the genus Maratus, have sharp vision and bold moves. Wolf spiders in the family Lycosidae run on the ground.
Crab spiders in Thomisidae, such as Misumena vatia, sit on flowers and ambush visitors.
Tarantulas, Trapdoor Spiders, And Huntsman Spiders
Tarantulas in Theraphosidae are large, hairy spiders that often live long lives. The goliath birdeater is one of the most famous.
Trapdoor spiders wait in hidden burrows. Huntsman spiders in Sparassidae, including the giant huntsman spider, are fast hunters with wide, flat bodies.
House Spiders, Cellar Spiders, And Orb-Weavers
House spiders such as Parasteatoda tepidariorum are common in homes and garages. Cellar spiders in Pholcidae, often called daddy long-legs, hang in loose webs.
Orb-weavers in Araneidae, including the golden silk orb-weaver Nephila clavipes, build strong circular webs.
Dangerous Spiders To Know By Name
Some dangerous spiders include black widow spiders in the genus Latrodectus, such as Latrodectus hesperus and the redback spider.
Brown recluse spiders in Loxosceles also pose a risk.
Australian funnel-web spiders in Atracidae, including the Sydney funnel-web spider, are well known.
Species like the banana spider can be venomous too.
