Crab Spider

Mecaphesa asperata

Crab spiders (family Thomisidae) are small hunting spiders that hold their long front legs open like a crab’s claws and wait on flowers to grab visiting insects. They don’t build webs to catch prey. The northern crab spider (Mecaphesa asperata), shown in the 3D model, is a bristly flower spider of North and Central America and the Caribbean. Its larger relative, the goldenrod crab spider (Misumena vatia), is famous for slowly changing between white and yellow.

Also known as northern crab spider, flower crab spider, Flower Spider

Crab spider abilities

10–25 days white → yellow (goldenrod crab spider)
The goldenrod crab spider, a relative of the spider in the model, can turn from white to yellow and back to match its flower. It is slow: turning yellow takes 10–25 days, and turning white about 6.
- The skin is see-through. White comes from guanine and uric acid inside the body, and yellow from tiny pigment granules (ommochromes) that build up in skin cells.
- To turn white again, the spider breaks down its yellow granules and recycles parts of them in the same cells. That is faster than building new pigment.
- Its eyes seem to be involved: their wide views can see the spider’s own body and the flower around it.
- Only some crab spiders do this, such as Misumena and Thomisus. We found no study showing it in the northern crab spider.
How long the goldenrod crab spider takes to change colour
White → yellow10–25 days
Yellow → white≈6 days
Upper end of the reported range. Timescale from a review, cited by Wikipedia.
Sources [2, 4, 6, 12, 13, 14]
2 pairs front legs held open
A crab spider sits still with its two long front pairs of legs spread wide, like open claws, ready to close on anything that lands.
- Holding the front two pairs of legs apart from the back two is one of the reasons for the name crab spider.
- The front legs are longer, heavier and spinier than the back legs.
- Bees seem to watch out for those legs. In one test, flowers with model crab spider legs got fewer bee visits than flowers with a model spider body alone.
Sources [1, 2, 15]
Head where prey is bitten
When an insect lands close enough, the spider snaps its spiny front legs shut and bites it near the head straight away.
- Prey includes honeybees, butterflies, flies and beetles, often bigger than the spider itself.
- Goldenrod crab spiders attacked bumblebees more often but caught honeybees more often.
- Young goldenrod crab spiders (7–15 mg) mostly struck small hoverflies (4 mg) on the head.
- Waiting is hard work: in two summers, about 1 in 5 female goldenrod crab spiders could not catch enough to lay eggs.
Sources [1, 4, 11, 16]
Harmless to people
Venom glands feed the fangs. The venom works fast on insects, but flower spiders are not dangerous to people.
- Venom and digestive juices turn the insect’s insides into liquid that the spider sucks up.
- The goldenrod crab spider’s fangs are reportedly too weak to get through human skin.
- Some unrelated spiders called “six-eyed crab spiders” are venomous relatives of recluse spiders. They belong to a different family.
- Never pick up a spider. Watching from close up is fine.
Sources [1, 2, 4]
UV ultraviolet that bees can seeStill debated
Bees see ultraviolet light, which people can’t. Some white crab spiders reflect it, so to a bee they may stand out on a flower. In Australian experiments, this seemed to lure honeybees in.
- Honeybees landed more often on daisies with white, UV-reflecting Australian crab spiders (Thomisus spectabilis). When scientists coated the spiders with a UV blocker, bees avoided those flowers.
- A later test found the lure only worked for large spiders with strong UV. Bees also turned away when the spider moved.
- For the goldenrod crab spider in the wild, matching the flower did not help it meet or catch more prey. Some visitors avoided spiders; bumblebees and honeybees mostly ignored them.
- Seen from far away, goldenrod crab spiders are hard for bees and birds to spot, but up close they are often visible. Scientists still debate what the colours are for.
What predators on flowers do to pollinators (meta-analysis)
Flower visits−36%
Time spent on flowers−51%
Average drop across many studies of flower predators, including crab spiders.
Sources [17, 18, 19, 20, 21, 22]
≈65% of her weight laid as eggs
A goldenrod crab spider mother folds a leaf into a little tent, lays one batch of eggs inside, seals it with silk and stands guard.
- She pulls the tip of a milkweed leaf underneath, ties it with silk and rests inside. A few days later she lays her eggs there.
- Her egg mass weighs about 146 mg, roughly 65% of her weight before laying.
- Guarding cuts down egg losses, mostly in the first half of nesting. While guarding she keeps losing weight.
- The young leave nearly a month later, and the mother often dies soon after. Northern crab spiders also lay a single egg sac, in late May or June.
A goldenrod crab spider mother just before laying ≈220 mg
Egg mass ≈146 mg (65%)
Averages from one Maine population.
Sources [8, 9, 23, 24]
Minutes until some spiderlings fly off
Young goldenrod crab spiders leave the nest and may float away on silk threads in the breeze. This is called ballooning.
- Spiderlings leave by ballooning, by moving on threads between plants, or by walking.
- From nests far from good hunting flowers, they often ballooned within minutes. On flowering goldenrod they stayed up to several days.
- Crab spiders have even reached the Hawaiian Islands. 17 of 18 Hawaiian Mecaphesa species come from just one or two arrivals, possibly about 10 million years ago.
Sources [25, 26]
3 ways forwards, backwards, sideways
Like a crab, a crab spider can scuttle sideways and backwards as well as forwards, slipping round the flower out of sight.
- This crab-like walk is one reason for the family’s name.
- Crab spiders with flat bodies hunt in cracks in tree bark or shelter under loose bark.
- Tiny males run from flower to flower looking for females. They move farther and more often than young females of the same size, and are often missing a leg or two.
Sources [2, 4, 27]

Tap a pin on the model or a part below.

2 pairs long, spiny grabbing legs
- The first two pairs of legs are longer, heavier and spinier than the back two. They work like a trap that snaps shut on an insect.
- All the legs curve forward in a crab-like way, which is where the name crab spider comes from.
- In the northern crab spider, two segments of each front leg carry red rings.
Sources [1, 2, 3]
- The two back pairs are shorter. They hold on to the flower while the front legs wait for prey.
- Crab spiders can scuttle sideways and backwards as well as forwards, a bit like a crab.
Sources [1, 2, 4]
Spiny short stiff bristles all over
- The northern crab spider’s body and legs are covered with many short, stiff spines. That is one way experts tell it from the smooth goldenrod crab spider.
- In its genus, Mecaphesa, these stiff hairs are longer and easier to see than in close relatives, and they run over the whole back.
- The area around the eyes is white.
Sources [3, 5]
8 eyes
- Crab spiders have eight eyes. In the goldenrod crab spider, four of them look at the space straight ahead at the same time.
- The two main eyes have a retina in three layers that can move. Scientists found at least two types of light sensors, including ones for green and ultraviolet light.
- Their wide views even let them see their own legs and body, which may help them match the colour of a flower.
Sources [4, 6]
Fast venom for insects
- A grabbed insect is bitten straight away near the head, and the venom works quickly.
- Venom and digestive juices turn the insect’s insides into liquid, which the spider sucks up. It leaves an empty but life-like shell.
- Flower spiders are not dangerous to people. The goldenrod crab spider’s fangs are reportedly too weak to get through human skin.
Sources [1, 4]
≈6 mm adult female, legs not included
- A female northern crab spider is about ¼ inch (≈6 mm) long. She is usually pale yellow, sometimes greenish, with dull red marks.
- The front half of the abdomen has red streaks on the sides. The back half has a mottled brown to red-brown V-shaped mark.
- In the goldenrod crab spider, a mother’s eggs can weigh about 65% as much as she did before laying them.
Sources [3, 7, 8]
- The palps are the short feelers beside the fangs.
- An adult male’s palps are large. He uses them to pass sperm to a female.
- Male northern crab spiders look like the females in colour and marks, but are only about half as long.
Sources [7]
- Crab spiders don’t build webs to catch prey, but they still make silk for safety lines and for their young.
- Goldenrod crab spider mothers use silk to seal a folded leaf around their eggs.
- Females leave silk draglines as they move, and males follow them to find a mate.
Sources [2, 4, 9]
2× more prey per day on milkweed (Misumena)
- Usually only one flower spider sits on a flower at a time.
- In Maine, goldenrod crab spiders stayed more than twice as long on milkweed as another crab spider did, and caught more than twice as much prey per day.
- Choosing good flowers matters: females that often hunted on poor flower heads laid fewer eggs.
Sources [1, 10, 11]
34% of prey weight was honeybees (one Maine study)
- Flower spiders catch honeybees, butterflies, flies and beetles that come for nectar.
- Goldenrod crab spiders attacked bumblebees more often, but actually caught honeybees more often.
- In one study on milkweed, honeybees made up about a third of the prey weight they caught. Moths were the next biggest share.
Sources [1, 10, 11]

Real crab spiders

Photos from Wikimedia Commons. Some of them can repaint the 3D model.

Northern crab spider, femaleAbout 6 mm long. Pale yellow or greenish with dull red marks: red streaks on the abdomen sides, a V-shaped mark behind and red rings on the front legs. Covered in short, stiff bristles.Hunts on flowers and lays a single egg sac in late springA young female northern crab spider. The fine bristles on its legs are easy to see.. Photo: AlaskaDave, CC BY-SA 3.0
A northern crab spider waiting on yarrow, VirginiaPhoto: Judy Gallagher, CC BY 2.0
Northern crab spider, Julie Metz Wetlands, VirginiaPhoto: Judy Gallagher, CC BY 2.0
Northern crab spider, Meadowood Farm, VirginiaPhoto: Judy Gallagher, CC BY 2.0
Northern crab spider in October, VirginiaPhoto: Judy Gallagher, CC BY 2.0
Goldenrod crab spider, yellowFemale Misumena vatia, 6–9 mm long, bright yellow from pigment granules in the skin, often with red stripes on the sides.Hunts on yellow flowers such as goldenrodA yellow goldenrod crab spider on a sunflower, Germany. Photo: Ermell, CC BY-SA 4.0
Goldenrod crab spider, whiteThe same species in its white form. Turning white takes about 6 days; the white shows through a clear skin.Young females often hunt on daisies and other pale flowersThe white form of the goldenrod crab spider, Dorset, England. Photo: Darth Newdar, CC BY-SA 3.0
A female goldenrod crab spider on yarrowPhoto: Luc Viatour, CC BY-SA 3.0
Face to face with a female goldenrod crab spider, FrancePhoto: Muséum de Toulouse, CC BY-SA 4.0
Northern crab spider, maleAbout half as long as the female, with similar colours and marks and large palps. In the goldenrod crab spider, males have brown or red front legs.Roams from flower to flower looking for femalesA tiny male goldenrod crab spider on feverfew, Belgium. Photo: DidierFy, CC BY-SA 4.0

Crab spider by the numbers

Measured by scientists, with comparisons you can picture.

Female body: ≈6 mm; northern crab spider, about ¼ inch⁠[7]; Female6 mmMale3 mm
Male body: ≈3 mm; about half the female’s length⁠[7]
Goldenrod crab spider: 6–9 mm; females; males only 3–4 mm⁠[4]
Male weight: ≈5 mg; adult male goldenrod crab spider (5.2 mg); Male5.2 mgFemale before laying220 mg; A mother about to lay (≈220 mg) weighs about 40 times as much⁠[27, 8]
Egg mass: ≈65%; of a goldenrod crab spider mother’s weight⁠[8]
White → yellow: 10–25 days; goldenrod crab spider; back to white ≈6 days⁠[4, 12]
Nest guarding: ≈1 month; until the young leave the folded leaf⁠[8]
Heat limit: 45.1 °C; northern crab spider can still walk properly up to here⁠[24]
Crab spider species: >2,100; in about 170 genera worldwide⁠[2]
Eyes: 8; four look straight ahead at once (goldenrod crab spider)⁠[6]

Crab spider myths and facts

Crab spiders are famous for camouflage. Here is what the evidence says.

0 of 8 answered

“Crab spiders are insects.”
“Crab spiders spin webs to catch their food.”
“Crab spiders can change colour in seconds, like a chameleon.”
“A crab spider’s eyes help control its colour change.”
“Matching the flower’s colour helps a crab spider catch more prey.”
“Crab spiders are dangerous to people.”
“Male crab spiders are much smaller than females.”
“Some crab spiders seem to attract bees with ultraviolet light.”

Crab spider records

Big numbers and superlatives, each checked against its source.

Tiny males
≈1%
Goldenrod crab spider
an adult male can weigh no more than 1% of a female full of eggs⁠[27]
All in on eggs
≈65%
Goldenrod crab spider
of a mother’s weight goes into her single batch of eggs⁠[8]
Heat-tough flower sitter
45.1 °C
Northern crab spider
heat limit, high compared with most other spiders tested⁠[24]
Island hoppers
17 of 18
Hawaiian Mecaphesa crab spiders
Hawaiian species descend from one or two arrivals, possibly about 10 million years ago⁠[26]
Big family
>2,100 species
Crab spiders (Thomisidae)
in about 170 genera, found worldwide⁠[2]

A crab spider’s life

The northern crab spider in New Jersey, with nest details from its cousin, the goldenrod crab spider.

Mid-April to May
Grown up
Northern crab spiders become adults in spring.⁠[24]
Late May to June
One egg sac
Each female lays a single egg sac.⁠[24]
About a month
Guarding
A goldenrod crab spider mother guards her folded-leaf nest until the young leave, nearly a month later.⁠[8]
June to July
Spiderlings out
Spiderlings come out. Some balloon away on silk; others walk to nearby flowers.⁠[24, 25]
Summer
First hunts
Young crab spiders hunt small flies on flowers, often striking them on the head.⁠[16]
Winter
Waiting it out
Northern crab spiders spend the winter as nearly grown young.⁠[24]
After the eggs
The end of a mother
Goldenrod crab spider mothers often die soon after their young leave.⁠[8]

Crab spider vs garden spider vs jumping spider

Three common spiders with three very different ways of catching a meal.

Crab spider vs garden spider vs jumping spider
	Crab spider	Garden spider	Jumping spider
Family⁠[2, 30, 31]	Thomisidae	Araneidae (orb-weavers)	Salticidae
Species⁠[2, 30, 31]	>2,100 in the family	One species, Araneus diadematus	About 7,000, the largest spider family
Female size⁠[7, 30]	≈6 mm (northern crab spider)	6.5–20 mm	Varies by species
Web to catch prey⁠[2, 30, 31]	No	Yes, a round orb web	No, hunts by sight
How it hunts⁠[1, 30, 31]	Waits on a flower and grabs visitors with its front legs	Waits in or near the web, then wraps prey in silk	Spots prey and makes agile jumps
Main hunting sense⁠[6, 30, 31]	Eyes: four look ahead at once	Touch: a signal line from the web	Eyes: two huge front eyes, among the best in arthropods

Sizes are body length without legs.

Is the crab spider endangered?

There is no sign of that, but nobody has checked. Neither the northern nor the goldenrod crab spider has an IUCN Red List assessment.

IUCN Red List

Not Evaluated (NE)

Trend unknown

The northern crab spider lives in North and Central America and the Caribbean.⁠[32, 33, 3]

Not evaluated (GBIF and Wikidata, checked 2026)

Threats

Fewer flying insects
Spiders that rely on flying insects can decline when insects do. In Switzerland, garden spiders fell to under 1% of their old numbers.⁠[34]
Too few good flowers
Crab spiders need busy flowers. Goldenrod crab spiders on poor flower heads laid fewer eggs, and some years about 1 in 5 females caught too little to breed.⁠[11]

What’s helping

Flowery gardens and meadows
Flowering goldenrod and milkweed are good hunting grounds. Spiderlings stay longer where flowers are in bloom.⁠[25, 10]
Look, don’t move them
Crab spiders choose their flowers carefully. Watching without touching lets them keep hunting.⁠[11]

Relatives

Goldenrod crab spider (Misumena vatia)Not Evaluated
Not assessed. Found in Europe and North America.⁠[35, 4]

Staying safe around crab spiders

Crab spiders are harmless to people. A few simple habits keep you and the spider safe.

Harmless
to people
Flower spiders are not dangerous to humans. Their venom is made for insects.⁠[1, 2]
Look
don’t touch
Watch from close up, but don’t pick a spider up or poke it. Never handle wild animals.
Name
mix-up
Some unrelated spiders are called “six-eyed crab spiders”. They are venomous cousins of recluse spiders, not flower spiders.⁠[2]
Shake
gardening gloves
Shake out gloves, shoes and clothes left outside before you put them on.⁠[36]
Wash
if bitten
Tell an adult. Wash the spot with soap and water, hold a cold, damp cloth on it and raise it if you can.⁠[36]
Doctor
if worried
If a bite gets very painful or swollen, get medical advice.⁠[36]

Crab spider quiz

12 questions. Every answer is somewhere on this page.

Question 1 of 12Score 0

What kind of animal is a crab spider?

Crab Spider field notes

Diet, food web, safety and badges from the Snappit field guide.

Diet & Feeding

Crab spiders are tiny hunters that love to eat other insects they catch on flowers!

Primary Foods

bees
flies
butterflies
moths
Foraging Method: Ambush

Ecological connections

HoneybeeHunts
Snatch bees visiting flowers for nectar.
HoverflyHunts
Ambushes flies that land on flowers.
Great TitPossible predator (Europe)
Birds such as great tits may eat crab spiders in Europe.

Safety

Danger 1/5 · Very low

Do not touch or pick up. Crab spiders are not dangerous to people, but tell an adult if you get bitten.

Traits

Collections

Classification

Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Thomisidae
Genus: Mecaphesa

Sources for these crab spider facts

36 studies and references · checked Oct 16, 2026

Frequently Asked Questions

How to identify Crab Spider?

Compare body proportions, leg shape, abdomen markings and the web, if there is one. Eye arrangement can be decisive but rarely shows up in a casual phone photo. A web is a supporting clue, not proof of who built it. Spider Identifier: upload a photo and compare the visible details.

How big is Crab Spider?

2-10 mm

How long does Crab Spider live?

60-365 days

What does Crab Spider eat?

Crab spiders are tiny hunters that love to eat other insects they catch on flowers!

Where is Crab Spider usually found?

Flowers and gardens

How does Crab Spider hunt?

Ambush

How many legs does Crab Spider have?

Are crab spiders dangerous to humans?

No. Flower spiders are not dangerous to people, and the crab spider family is not known to be harmful. Their venom works on insects. Still, don’t pick them up, and tell an adult if anything bites you.

Do crab spiders make webs?

Not to catch prey. Crab spiders ambush insects on flowers instead. They still make silk for safety lines, draglines and egg nests, and their young float away on silk.

How do crab spiders change colour?

Only some can, such as the goldenrod crab spider. It builds yellow pigment granules in its skin cells to turn yellow, which takes 10–25 days, and breaks them down to turn white in about 6 days.

What do crab spiders eat?

Insects that visit flowers, such as honeybees, bumblebees, moths, butterflies and flies. They often catch insects bigger than themselves.

Why are they called crab spiders?

Because of their crab-like shape, the way they hold their long front legs apart from the back ones, and their ability to scuttle sideways or backwards.

How big is a northern crab spider?

A female is about ¼ inch (≈6 mm) long, not counting her legs. A male is only about half as long.

Where do northern crab spiders live?

In North and Central America and the Caribbean, usually on flowers where they wait for insects.

Is a crab spider an insect?

No. Spiders are arachnids. They have eight legs, while insects have six.