arachnid

Images, Videos & Interactives

A brown Buthus scorpion with its tail arched over its back and stinger raised, standing on a piece of wood.

Illustration showing eight types of mites and ticks, each labeled with their common and scientific names, including tropical rat mite, Opilioacarus texanus, Holothyrus legendrei, fur mite, black-legged tick, soil mite, itch mite, and American house-dust mite.

Chart titled Diversity of arachnids comparing a Silurian fossil scorpion and 11 living groups, including spiders, scorpions, mites, daddy longlegs, sunspiders, whip scorpions, and false scorpions. Illustrations show their varied forms and typical size ranges from 0.1 millimeters to 210 millimeters; fossil anatomy labels identify pincers, pedipalps, legs, and body sections.

Tailless whip scorpion

Illustration of a ricinuleid, a small arachnid in the order Ricinulei, showing its segmented brown body, eight jointed legs, and distinctive shield-like structure on its back.

Illustration of a palpigrade arachnid (order Palpigradi), showing its small, segmented body, eight legs, and a long, thin, bristle-covered tail. Size range is 0.8 to 2.6 millimeters.

Illustration of a daddy longlegs, or Opiliones, showing its small, rounded body and extremely long, thin legs, characteristic of this arachnid order.

A detailed top view of a schizomid arachnid (order Schizomida), showing its segmented, striped abdomen, elongated legs, and small pincers, measuring about 5 to 7 millimeters long.

A man sleeps with his mouth open on a bed, while a large spider sits on the pillow near his hand.

Crazy in Love: Why Some Animals Eat Their Mates

At a Glance

garden spider

arachnid summary

arachnid: Media

arthropod

Videos

A man sleeps with his mouth open on a bed, while a large spider sits on the pillow near his hand.

Do We Really Swallow Spiders in Our Sleep?

This myth is based on a web of lies.

Video: Encyclopædia Britannica, Inc.

Crazy in Love: Why Some Animals Eat Their Mates

Crazy in Love: Why Some Animals Eat Their Mates

Love can be a dangerous game.

Video: Encyclopædia Britannica, Inc.

Watch a water spider create its underwater house

Watch a water spider create its underwater house

A water spider (Argyroneta aquatica) building its diving bell. The spider...

Video: © Claude Nuridsany and Marie Perennou/Science Source

Images

A brown Buthus scorpion with its tail arched over its back and stinger raised, standing on a piece of wood.

Venomous arachnid

A scorpion (Buthus species) in a defensive posture.

© Mauro Rodrigues/stock.adobe.com

Illustration showing eight types of mites and ticks, each labeled with their common and scientific names, including tropical rat mite, Opilioacarus texanus, Holothyrus legendrei, fur mite, black-legged tick, soil mite, itch mite, and American house-dust mite.

Diversity of Acari

Representative members of subclass Acari, which includes mites and ticks.

Encyclopædia Britannica, Inc.

Chart titled Diversity of arachnids comparing a Silurian fossil scorpion and 11 living groups, including spiders, scorpions, mites, daddy longlegs, sunspiders, whip scorpions, and false scorpions. Illustrations show their varied forms and typical size ranges from 0.1 millimeters to 210 millimeters; fossil anatomy labels identify pincers, pedipalps, legs, and body sections.

Arachnid diversity

A sampling of the diversity of arachnids.

Encyclopædia Britannica, Inc.

Tailless whip scorpion

Tailless whip scorpion

Damon diadema, a species of tailless whip scorpion, in a cave near the Loboc...

Thomas Brown

Illustration of a ricinuleid, a small arachnid in the order Ricinulei, showing its segmented brown body, eight jointed legs, and distinctive shield-like structure on its back.

Ricinuleid

Members of the order Ricinulei are ticklike arachnids.

Encyclopædia Britannica, Inc.

Illustration of a palpigrade arachnid (order Palpigradi), showing its small, segmented body, eight legs, and a long, thin, bristle-covered tail. Size range is 0.8 to 2.6 millimeters.

Palpigrade

Micro whip scorpions are palpigrades—members of the order Palpigradi.

Encyclopædia Britannica, Inc.

Illustration of a daddy longlegs, or Opiliones, showing its small, rounded body and extremely long, thin legs, characteristic of this arachnid order.

Daddy longlegs

Members of the order Opiliones are known as daddy longlegs, or harvestmen.

Encyclopædia Britannica, Inc.

A detailed top view of a schizomid arachnid (order Schizomida), showing its segmented, striped abdomen, elongated legs, and small pincers, measuring about 5 to 7 millimeters long.

Schizomid

Sprickets, or short-tailed whip-scorpions, are members of the order Schizomida.

Encyclopædia Britannica, Inc.

Daddy longlegs

Daddy longlegs

A daddy longlegs, or harvestman (order Opiliones).

AdstockRF

A brown nursery web spider from the Pisauridae family clings to green leaves while carrying a round white egg sac beneath its body.

Nursery-web spider

A female nursery-web spider carrying her egg sac.

© JustNatureChannel/Dreamstime.com

Close-up of a female Lone Star Tick, Amblyomma americanum, showing a distinct white spot on its reddish-brown back, perched on a green leaf.

Lone star tick

A female lone star tick (Amblyomma americanum) sporting the white dorsal...

© Jason Ondreicka/Dreamstime.com

Diagram of the life cycle of the black-legged tick (Ixodes scapularis), showing seasonal stages from engorged female laying eggs in spring, larva and nymph stages feeding on animal and human hosts in summer, and adult ticks on hosts in fall and winter. Arrows indicate progression through each stage, with illustrations of ticks and typical hosts such as deer, horses, dogs, and humans.

Tick life cycle

The life cycle of the hard tick Ixodes scapularis, a carrier of the bacterium...

Encyclopædia Britannica, Inc.

Protective mother

Protective mother

A female lynx spider (Hamadruas species) guarding her newly hatched offspring....

© Osoioo/Shutterstock.com

Illustration showing dorsal and ventral views of a scorpion (Scorpiones), with body parts labeled including eyes, claws, pedipalps, stinger, legs, pectines, spiracles, and reproductive structures.

Scorpion

The dorsal and ventral views of a scorpion.

Encyclopædia Britannica, Inc.

Labeled diagram of a spider showing its external anatomy, including the cephalothorax, abdomen, eyes, legs, fangs, pedipalps, spinnerets, and other key body parts.

External organization of a spider

An illustration of the external organization of a spider.

Encyclopædia Britannica, Inc.

Diagram showing the anatomy of a pseudoscorpion from both dorsal and ventral views, with labeled body parts including pedipalps, eyes, carapace, legs, chelicerae, spiracles, and other key features.

Pseudoscorpion

Anatomy of a pseudoscorpion (or false scorpion).

Encyclopædia Britannica, Inc.

Labeled cutaway diagram of a spider's internal anatomy, showing the brain, venom glands and ducts, sucking stomach, gut ceca, heart and aortae, digestive tract, book lungs, tracheae, silk glands, ovaries, spermatheca, spinnerets, and reproductive openings.

Spider anatomy

Internal organization of a spider.

Encyclopædia Britannica, Inc.

Illustration showing a cross section of a spider's book lung, with layered lamellae for gas exchange, blood flow between the layers, and air entering through a spiracle opening.

Book lung

Diagrammatic section through a book lung.

Encyclopædia Britannica, Inc.

arachnids

arachnids

Most arachnids have four pairs of legs as well as other appendages for capturing...

© Artush—iStock/Getty Images

Diagram of the tree of life based on the three-domain system, showing Archaea, Bacteria, and Eukaryota branching into four kingdoms: Plants, Animals, Fungi, and Protista, with illustrations of representative organisms for each group.

The three-domain classification of life-forms

The tree of life according to the three-domain system of biological classification,...

Encyclopædia Britannica, Inc.

garden spider

garden spider

Garden spider (Araneus diadematus).

© Artush—iStock/Getty Images

Interactives

Arthropod diversity

Arthropod diversity

Explore the major groups of athropods and the largest insect families with this interactive.

Encyclopædia Britannica, Inc.

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