Are Crab Spiders Poisonous? What You Need to Know

Crab spiders are commonly found lurking in gardens and flower beds, acting as a natural pest control agent.

These spiders have their first four legs longer than the back four, held out to the sides, which gives them a crab-like appearance. They can walk forwards, sideways, or backward ¹.

With their ability to camouflage among flowers, they skillfully catch and devour various insects, including bees and flies. These fascinating spiders may lead one to wonder whether they are poisonous.

The venom of many crab spiders is indeed more potent than most other spiders, allowing them to immobilize their prey swiftly.

Do Crab Spiders Bite Humans?

Crab spiders possess venom rather than poison, and their venom isn’t harmful to humans. Due to their small size, their fangs usually cannot break the skin.

While the larger crab spiders from the Sparassidae family can induce mild illness in humans, it’s generally not severe enough to require hospitalization.

So, even though they may be venomous towards their prey, they pose very little threat to people.

Are Crab Spiders Poisonous?

Venomous vs Poisonous

Crab spiders are venomous rather than poisonous. The distinction between the two is:

• Venomous: Injects venom through bites or stings
• Poisonous: Harmful when ingested or touched

Crab spiders use their venom to immobilize prey, but it is generally not dangerous to humans.

Bites and Effects on Humans

Crab spider bites are rare but possible. If bitten, humans might experience:

• Mild pain or discomfort
• Swelling at the site of the bite
• Itchiness

However, these symptoms are usually temporary and brief.

Danger Levels and Precautions

Crab spiders are not considered dangerous to humans. They are more focused on hunting insects, such as bees and flies, and are beneficial to gardens as a natural form of pest control.

To prevent bites, take precautions like:

• Wearing gloves when gardening
• Checking for spiders before reaching into hidden areas
• Avoiding handling spiders directly

Venomous Spiders	Non-Venomous Spiders
Black Widow	Crab Spider
Brown Recluse	Daddy Longlegs

There is no need for extreme precautions when encountering crab spiders, but do take basic safety measures to avoid getting bitten. They are a helpful ally in controlling other insect pests in your garden.

Understanding the Crab Spider Family

Crab spiders are small to medium-sized spiders, measuring about 0.5 inches long. Their body colors range from yellow or red to brown or gray.

Crab Spider Family

Crab spiders belong to the family Thomisidae. They are considered beneficial to people as they eat many insect pests found in gardens and flower beds.

Interestingly, scientists believe that the venom of many crab spiders is more potent than most spiders, allowing them to quickly subdue prey such as bees.

Genera and Species

There are several genera and species of crab spiders found around the world. Here are a few examples:

• Xysticus – Ground crab spiders, usually dull gray and brown with rusty, tan, white, or yellow markings ³
• Misumena – Flower crab spiders, typically found on flowers waiting for their prey ⁴
• Thomisus – well-known for their ability to change color to camouflage, often found on flowers or leaves ⁵

Table showing different species of crab spiders

Genus	Species	Common Name	Habitat
Xysticus	Various species	Ground crab spiders	Ground, foliage
Misumena	Misumena vatia	Flower crab spiders	Flowers
Thomisus	Thomisus onustus, others	Color-changing spiders	Flowers, leaves

Crab Spider: Biology and Behavior

Camouflage and Hunting

Crab spiders exhibit excellent camouflage abilities, allowing them to blend in with their surroundings by adjusting their body color.

They typically hunt during the day and patiently wait for their prey, such as insects.

Main features of crab spider camouflage:

• Change of colors
• Blending with surroundings
• Daytime hunting

Mating and Reproduction

The reproduction process in crab spiders consists of a male approaching a female and engaging in a mating ritual.

After mating, the female lays eggs in a secure location, such as leafy areas or plant stems.

Habitat and Distribution

Crab spiders belong to the genus Xysticus and are commonly found in various environments, including gardens, forests, and grasslands.

They are distributed across different geographic regions, inhabiting places with abundant vegetation.

Common Crab spider habitats:

• Gardens
• Forests
• Grasslands

Comparing crab spider habitats

Habitat	Pros	Cons
Gardens	Abundant prey, camouflage	Human intervention, pesticide use
Forests	Diverse vegetation	Competition from other predators
Grasslands	Open spaces for hunting	Limited hiding spots for protection

Crab Spider Interaction with the Environment

Flower Crab Spiders

Flower Crab Spiders are known for their ability to camouflage by matching the color of the flowers they inhabit. They patiently wait for their prey, like bees, making them efficient predators in gardens.

Benefits and Roles in Gardens

• Flower Crab Spiders are beneficial for garden pest control.
• They reduce pest populations by preying on harmful insects.
• Their presence encourages biodiversity and contributes to a healthy garden ecosystem.

Pest Control and Population Management

Crab spiders play a vital role in managing insect populations in gardens. They are considered a natural form of pest control.

Crab spiders in pest controlling

Pros	Cons
Natural form of control	May reduce pollinator populations
Reduces use of pesticides	Habitats may be limited to certain flowers

These spiders help maintain a balance in the ecosystem by keeping harmful pests in check. However, it’s important to keep in mind that their presence may also affect pollinator populations.

Therefore, crab spiders play a crucial role in the garden ecosystem and deserve attention for their contributions to pest management.

Other Interesting Facts and Features

Sexual Dimorphism and Size

• Female crab spiders are generally larger than males
• Males have longer leg to body size ratio

Comparison Table: Female vs Male Crab Spiders

Attribute	Female Crab Spiders	Male Crab Spiders
Size	Larger	Smaller
Leg to body ratio	Shorter legs, larger body	Longer legs, smaller body
Color changing	Yes, in some species	Yes, in some species
Hunting habits	Ambush predators	Ambush predators

Feeding Habits and Diet

Crab spiders are ambush predators, meaning they do not spin webs to catch their prey². Instead, they rely on their ability to blend in with their surroundings by changing colors³.

Their diet mainly consists of insects like bees and flies that they camouflage and wait for their prey to approach, then quickly attack.

Variety of Colors and Patterns

Crab spiders exhibit a variety of colors and patterns, depending on their species and habitat⁴. Common colors include yellow, white, green, and brown.

Patterns vary and help them camouflage themselves in their surroundings. Some species even have the ability to change color to better blend in with their environment³.

To summarize:

• Common crab spider colors are yellow, white, green, and brown
• Patterns vary between species
• Some can change color

Conclusion

Crab spiders, while often sparking curiosity about their potential toxicity, are welcome visitors in gardens and flower beds. They serve as nature’s pest controllers.

With their adept camouflage skills, they efficiently capture and devour various insects, contributing to biodiversity and ecosystem health. While their venomous nature aids in subduing prey, they pose minimal risk to humans.

The information presented in this article sheds light on the intriguing world of crab spiders, showcasing their essential role in maintaining a balanced garden environment.

Footnotes

1. UMN Extension ↩ ↩²
2. Maryland’s Wild Acres ↩ ↩²
3. Missouri Department of Conservation ↩ ↩² ↩³
4. UMN Extension ↩ ↩²
5. Thomisus onustus ↩

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about crab spiders. Scroll down to have a look at some of them.

Letter 1 – Crab Spider

Bright yellow spider
May 23, 2010
I found this spider on top of my trash can. Never seen one like this before, very bright yellow. Can you identify? For some reason he intrigued me a lot.
Thank you for your time!!
Seattle, WA

This is a Crab Spider.  They are frequently found on blossoms waiting for prey, and the coloration acts as camouflage on brightly colored flowers.

Letter 2 – Crab Spider

Chillin’ Green Spider
December 8, 2009
What is this spider that i found, chilling on my side-view mirror? He was pretty cool, just kinda sunbathing and not really caring about anything. When i put him on a leaf and put him in the grass, he immediately laid himself out and started sunbathing again.
-wes-
alamo, california

Hi -wes-,
This is a Crab Spider in the family Thomisidae, but we are uncertain of the exact species.  You may find out more information on Crab Spiders and browse through many images on our site as well as on bugGuide.

Letter 3 – Anglewing and Crab Spider: Food Chain!!!

A comma makes a full stop.
Spotted this Comma butterfly on Buddleia during a summer mid – afternoon whilst taking some garden shots. I was intrigued to see it in the same position, some two hours later.

Closer inspection revealed it in the clasp of a pure white crab spider obviously lying in wait for its next victim.
Paul Dobrée – Carey
Dorset, England, UK

Hi Paul,
What a lovely addition to our new Food Chain page.

Letter 4 – Crab Spider

Crab/flower spider
I was so excited today, when I went out to admire my roses, and found a cool white spider with pink lightning bolts down it’s side! I’d seen spiders of a similar shape, but not with this neat-o, new-wave color palate, and never in the middle of their lunch.

I grabbed my camera snapped a couple pics, and immediately came back inside to google white and pink spider. Your site came up, and I started looking through it. That was 3 hours ago. What a great site you have!! Well – now I know what my spider is, as well as so many other critters I’ve seen about my house, here in Seattle, WA.

I noticed you don’t have too many entries from this part of the country, though, and I’ve seen some interesting creatures that I couldn’t find on your site. Now that I know you’re here, I’ll keep my camera handier, so that when I do see new fascinating friends, I can get your help in naming them for me. Thanks for your wonderful site!!
Michelle

Hi Michelle,
I’m so happy our site was both helpful and entertaining.

Letter 5 – Bug of the Month: March 2008 – Giant Crab Spider with Spiderlings

What Kind of Spider is This?
Hello,
I friend has this spider in his house in LA, California, see attachment. What kind is this, it looks to be over 2″ in length.
Craig Baugher

(03/01/2008) i officially have the creeps
hi:
this photo has given me the willies, big-time: could it be real? enhanced? photoshopped? just tell me it’s nowhere in north america.
cheers,
nick

Hi Craig and Nick,
Interestingly, you both sent us the same photo for identification. This is a female Giant Crab Spider in the family Sparassidae, probably the genus Olios. Nice image of the maternal behavior. We have read that the mother spider shares prey with her spiderlings.

We are so intrigued with this image, and also amused that two different people requested the identification, so we decided to make it our Bug of the Month for March. By the way Nick, Craig says it was photographed in Los Angeles. Giant Crab Spiders in the genus Olios are shy, nocturnal hunters and they are harmless. They will actually help rid a home of cockroaches.

Letter 6 – Banana Spider or Giant Crab Spider

I live in the central west coast of Florida (near Tampa bay) and I found this spyder in the bathroom high up in the corner. The wife says she thinks it’s a poisonous bananna spyder (we do have quite a few bannana trees) because she say’s they jump, I’ve never witnessed this.

But this is not the first I’ve seen these. But never do I see a nest making me think it’s a “wolf” or a “fishing spyder”. We do have large web making spyders and the one in question spins a web but, I’m still doubious.
The doubting spyder houser….
May the love of God be with you and yours,
Respectfully,
Glenn T. Ennis

Hi Glenn,
Your wife is partly correct. You have a Giant Crab Spider, probably Heteropoda venatoria, a female. They are sometimes called Banana Spiders because they are sometimes imported with bunches of bananas and people mistake them for tarantulas.

The species if found worldwide in tropical regions, but is also common in Florida. They often enter homes where they are content to feed on cockroaches, hence they are beneficial. The female will carry her egg sac around with her until the spiderlings hatch. They are harmless to humans.

Letter 7 – Crab Spider

This bug looks like a kernal of corn. We found it crawling on our lawn furniture in Pleasant Valley, PA. What is it?
thanks,
Lynne Otrok

Hi Lynne,
This is a Crab Spider in the genus Misumena. These spiders do not build webs, but usually wait on flowers to ambush their flying prey. The spiders have some camoulfage ability, changing colors with their surroundings. Perhaps yours just stepped off of a sunflower.

Letter 8 – Crab Spider

Hello
I hope your site is still active. I’m thinking this is a crab spider – not sure. I am located in Kelso, Wa. Can you tell me what it is? Thanks so much,
Betty Van Riper

Hi Betty
This is indeed a Crab Spider, Misumena vatia, also called a Flower Spider. Your specimen shows one of the most distinct color variations.

Letter 9 – Crab Spider

I.D. a Crab-like spider
I’m a big fan of most spiders but on Tuesday, May 15, 2007, southcentral Wisconsin, while washing dishes, I suddenly felt a stinging sensation in the upper part of my back. Quickly taking my sweatshirt and t-shirt off I shook them and suddenly had this cheery looking critter drop out onto the kitchen floor.

With a quick crab-like locomotion it started to head for the under part of the fridge.I corralled it and scooped it up into a cylinder. As a precaution, I put it in the freezer (I know, I know) not sure of what I had or what type of reaction I was going to have to the bite. I have not found anything online and while looking, stumbled across your site. I hope the pictures make it through the servers.

If not, the best description I can give is, very crab like profile with the “second” appendage longer than the rest, eight eyes in a two-four-two configuration, predominantly dark red to black in coloration, some tan colors on the abdomen, legs seem almost translucent in appearance towards the ends, spiky hairs on most of the legs, and upon closer inspection just looks down right ugly by spider standards. A coupon for your troubles to the local coffee shop if you can i.d. it or even if you can’t.
m-
(college ruled)

Hi M,
This is indeed a Crab Spider in the family Thomisidae. It is possibly in the genus Xysticus as pictured on BugGuide. The college ruled background is awesome.

Letter 10 – Crab Spider

Crab spider
Hi bugman,
Just a pic taken this morning on an early purple orchid, taken in our garden in the Dordogne region of France, great site, thanks
Jeff Warrington

Hi Jeff,
What a wonderful image! Crab Spiders are also known as Flower Spiders and are able to change color to match their surroundings. Your spider is quite the rebel, standing out so boldly.

Letter 11 – Crab Spider

misumenoides formosipes?
Greetings,
First, thank you for such an awesome resource! I’ve spent many, many hours here…
It was a pure stroke of luck that I ran across this beautiful specimen… we stopped at a rest area near Tallahassee on I-10 and I decided to take a quick walk around. I thank the random palm seedlings growing in the curb for catching my attention and leading me to it.

I did some research and found a similar spider, but it was grouped with several others and none of them really looked alike. Misumenoides formosipes is what BugGuide had to say, but the ‘whitebanded crab spider’ is what gets me… the little bugger is absolutely free of white colouration.
Thanks,
Jeff Wright

Hi Jeff,
There is a great deal of individual variation with some species of spiders. We agree that this is probably Misumenoides formosipes, or at least a closely related species of Crab Spider.

We did find a very close match on BugGuide.  The common names of insects are sometimes appropriate, and sometimes not. We will be posting your letter and gorgeous photo, but as we are currently migrating our site, we are not certain when the post will go live.

Letter 12 – Bark Crab Spider perhaps

Itty bitty crumb spider
Hi again! You were so wonderful to identify my folding door spider! I have registered for your site, and logged in numerous times, but it won’t allow me to comment, says that I am not logged in, or else I would have thanked you right away!

This little bitty guy is very cute and lives on our computer monitor, he’s only slightly bigger than a jumping spider size wise, and that’s only because of his leg span. I found he tended to hold out his 2 front legs like a tiny crab.
Holly Claire
Victoria, vancouver island, BC

Hi Holly,
It is interesting that you compared your spider’s appearance to that of a crab, because it is definitely a Crab Spider in the family Thomisidae. We believe it may be a Bark Crab Spider, as it is a pretty convincing match to an image of Bassaniana versicolor posted to BugGuide.

We are not sure why you are having problems with posting comments. We will refer your problem to our web host to see if he has a solution.

Letter 13 – Crab Spider

Tiny pale green spider on forest floor…
Thu, Oct 30, 2008 at 9:27 AM
I was examining a scrape on the forest floor, looking for hair when I found this tiny little spider! It coudnt be bigger than a centimeter across the longest point (wish I had had a coin with me for size reference).

It walked sideways like a crab. When disturbed it pulled its legs in and tried to look inconspicuous. After I got done taking pictures it crawled to the underside of a leaf and hid.
Dana
Athens, Georgia

Hi Dana,
This is a Crab Spider in the family Thomisidae.  We are not certain of the genus or species, but we would hesitate a guess at the genus Misumenops as evidenced by images posted to BugGuide.  Crab Spiders do not build hunting webs.  They ambush their prey using camouflage techniques.

Letter 14 – Correction: Crab Spider, not Jumping Spider

What is this?
Location: Sub-tropical rainforest area, Central Coast, Australia
December 9, 2011 10:59 pm
There’s a lot of weird bugs at my boyfriend’s house that I’ve never seen before, which is interesting because I grew up only a few kilometres away on a really similar property.

Still, we saw this on the roof of my car and couldn’t figure out what on earth it is. It probably looks rather unproportionate in the picture, but each one of the long arms at the front was about 1 1/2 inches long. Not only is it creepy looking, it moves really damn quick.
Help?!
Signature: – Mel

Hi Mel,
We believe this is some species of Jumping Spider in the family Salticidae.  We have not had any luck determining the species.

Possible Correction
Trevor sent in a comment that he suspects because of the paired front legs that this may be a Crab Spider.  There is a photo on the Brisbane Insect and Spider website that is called a Peak Crab Spider in the genus Tmarus or Sidymella that looks very similar.  FlickR also has an image of Sidymella.

Letter 15 – Crab Spider

Spider?
First, this is an awesome sight. I have spent hours looking at the pictures and finding out about all these bugs I didn’t know existed. As for my bug…I live in Los Angeles and found this little guy on my counter while I was putting some flowers in a vase.

I think it’s a spider but it appears to only have 6 legs and I thought spiders have 8. It did however release some sort of silk when I was trying to get it onto a branch. It sat on this flower for a while with it’s two long front legs stretched out. It also seemed to be eating something off the flower.
What is it?
Thanks!
Elena DiMeo

Hi Elena,
You have a species of Crab Spider, Family Thomisidae. They are sometimes called Flower Spiders because they wait for prey on blossoms. Here is a good site with many great Crab Spider photos.