Crab Spiders in Colorado: What to Do and How to Coexist Safely

Crab spiders are fascinating creatures often found in Colorado. These arachnids are known for their crab-like appearance and unique hunting tactics. As they play a crucial role in controlling the insect population, understanding their behavior and how to handle an encounter with one can be beneficial for both people and the environment.

Many crab spiders have an impressive ability to camouflage themselves, blending seamlessly into their surroundings. This skill makes them effective ambush predators, lying in wait for unsuspecting prey to pass by. When you spot one in your Colorado garden or home, there’s no need to panic; crab spiders are not aggressive and pose no significant threat to humans.

If you come across a crab spider, it’s essential to appreciate their role in the ecosystem and practice safe handling techniques. Gently coaxing the spider onto a sheet of paper and relocating it outside can help maintain harmony between our shared spaces and these remarkable little creatures.

Crab Spiders in Colorado

Identification and Characteristics

Crab spiders belong to the family Thomisidae and are known for their crab-like appearance and sideways movements. Here are some key features to identify them:

• Eight legs with the front two pairs being longer and more robust
• Eight eyes arranged in two rows
• Body size ranging from 2 to 10 mm
• Lack of prominent web-making abilities

In Colorado, one may encounter species like the Goldenrod Crab Spider (Misumena vatia), which exhibits interesting color-changing abilities depending on its environment. Over a period of 6 to 25 days, they can change from white to yellow or vice versa to blend in with their surroundings better.

Habitat and Range

Crab spiders can be found in a variety of habitats throughout Colorado. Their range spans across gardens, fields, forests, and homes, where they act as essential biological control agents by feeding on insect pests. Here’s a quick overview of their habitat and range:

• Native to Colorado and found in drier areas below 7500 feet
• Active during the day, using their camouflage to ambush prey
• Attracted to colorful flowers, where they wait for pollinating insects

To summarize, crab spiders in Colorado are fascinating creatures with unique characteristics. They play a crucial role in maintaining the ecosystem by controlling insect populations. It’s crucial to understand their appearance, behavior, and habitat to appreciate their presence in the state.

Behavior and Diet

Hunting and Camouflage

Crab spiders, known for their hunting abilities, mainly rely on ambush tactics instead of using webs. They often use their versatile color-changing ability to blend in with their surroundings (source). For instance, the Goldenrod Crab Spider can change its color:

• From white to yellow in 10-25 days
• From yellow to white in 6 days

This camouflage allows them to hide effectively on leaves, grass, and flowers, waiting for their prey to come close before striking.

Prey and Predators

The primary diet of crab spiders consists of various insects, such as:

• Bees
• Mosquitoes
• Wasps
• Flies

As natural predators, crab spiders contribute significantly to the biological control of insect pests in gardens, fields, and homes (source). However, they also have their own set of predators, including:

• Birds
• Larger spiders
• Insect-eating mammals

In summary, crab spiders are master hunters with excellent camouflage abilities that enable them to capture their insect prey effectively. Their behavior and diet contribute to a vital ecological balance, emphasizing their importance in the ecosystem.

Color-changing abilities of the Goldenrod Crab Spider:

Reproduction and Life Cycle

Mating and Egg Laying

• Female crab spiders attract mates by producing pheromones
• Mating occurs in spring or early summer

Female crab spiders produce chemical signals called pheromones to attract males for mating. Mating usually takes place in the spring or early summer. Once they have mated, the females will create nests to lay their eggs securely. These nests often have a silken egg sac to protect and secure the eggs.

Spiderlings and Molting

• Eggs hatch into spiderlings after a few weeks
• Molting occurs as spiderlings grow and develop

After a few weeks, the eggs hatch into spiderlings. As these spiderlings grow, they undergo a process called molting. Molting involves shedding their outer skin to accommodate their growing bodies. These molts are crucial for the spiderlings to develop and transform into adult crab spiders.

Safety and Interactions with Humans

Bite Symptoms and Treatment

Crab spiders in Colorado are generally harmless to humans. Although they might bite in self-defense, their venom is not dangerous for humans. Symptoms of a crab spider bite are:

• Mild pain
• Swelling
• Redness

To treat a crab spider bite, follow these steps:

1. Clean the bite site with soap and water.
2. Apply a cold pack if there’s swelling.
3. Take over-the-counter pain relief if needed.

If you suspect an allergic reaction, consult a doctor promptly.

Comparison with Other Spiders

Crab spiders are often mistaken for other, more dangerous spiders native to Colorado. Here are a few common spiders found in the state:

• Black Widow Spider: Venomous, painful bite, females have a red hourglass pattern on their abdomen.
• Brown Recluse Spider: Venomous, necrotic bite, has a violin-shaped marking on its head.
• Daring Jumping Spider: Harmless, black with white markings and iridescent green jaws.
• Yellow Sac Spider: Non-aggressive, mildly venomous, can cause swelling and burning at the bite site.

Wolf spiders, hairy spiders, and cellar spiders (Pholcidae family) are also found in Colorado. While they might look intimidating, they are not harmful to humans:

• Wolf Spiders: Visually scary, but timid and harmless.
• Hairy Spiders: Appear menacing with their hair, but are non-aggressive.
• Cellar Spiders (Pholcidae): Long legs, prefer dark, damp spaces, and pose no threat to humans.

Keep in mind that although most spider bites are not severe, some individuals might experience an allergic reaction or infection. Always practice caution while interacting with spiders and seek medical attention if necessary.

Crab Spiders in Gardens and Homes

Beneficial vs. Pests

Crab spiders, especially those from the Family Thomisidae, are considered beneficial arthropods in gardens, as they help control insect pests by feeding on them. They blend in with plants like the Misumena vatia, waiting to capture their prey. In contrast, pests such as yellow sac spiders and wolf spiders (Lycosidae), can be invasive and destructive to plant life.

Some key features of crab spiders:

• Have front legs longer than other legs
• Do not spin webs to capture prey
• Nocturnal hunters

Examples of beneficial and pest spiders:

• Beneficial: Crab spiders (Family Thomisidae)
• Pests: Yellow sac spider, Wolf spider (Family Lycosidae)

Control and Management

While crab spiders are generally helpful in the garden, it may be necessary to control them if their population increases excessively or if they enter your home.

Habitat modification

• Remove debris and woodpiles
• Keep ground cover plants away from the foundation of your home
• Seal gaps and cracks around doors and windows

Physical removal

• Use a vacuum cleaner to remove spiders and egg sacs from corners of rooms and ceilings
• Use glue traps for capturing wandering wolf spiders and yellow sac spiders

Remember to appreciate the beneficial crab spiders in your garden, as they play their role in maintaining a balanced ecosystem by preying on pests that could harm your plants. However, if their presence becomes a concern, follow the control and management techniques mentioned above.

Resources for Identifying and Understanding Crab Spiders

Field Guides

A good field guide is essential for identifying and understanding crab spiders in Colorado. Some recommended options:

• Example Field Guide 1: This guide helps identify spiders by color, range, and other characteristics. Pros: Easy-to-use, comprehensive. Cons: Limited to a specific region.

• Example Field Guide 2: A more general guide to spiders, including web-building species. Pros: Covers a wide variety of organisms. Cons: May not have specific information about Colorado crab spiders.

Online Resources

There are various online resources available for identifying and understanding crab spiders. Here are a few:

1. Extension: Provides information on brown recluse spider identification and similar-looking spiders in Colorado.

2. Spiders in the Home: Offers general information about spiders, including their benefits in controlling insect pests.

3. Goldenrod Crab Spider: Information about this specific species, including color changes and distribution.

Remember, when identifying and dealing with crab spiders in Colorado, always stay safe and follow appropriate precautions.

Reader Emails

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

Letter 1 – Crab Spider

Spider in Alabama
Hi Bugman,
I live in Alabama, and have recently found 3 spiders in my home in the last 2 days. Two of them were the same type, and one (the one I have the picture of) was of a different type. I wish I had a picture of the first type because it was the frightening looking one, about the size of the quarter, not hairy, didn’t look like a wolf spider to me, but what do I know? I’ll be on the lookout and if another one comes along I’ll be sure to snap a picture of it (but hopefully won’t have to do so). Anyway, here is the picture of the second one. The two pictures are of the same spider; they look different because one I used the flash and it washed all the color out and made the spider look gray. It’s actually colored more like the orange looking picture. Sorry the pictures aren’t great quality; my digital camera doesn’t do macro work too well. Can you tell me what kind it is? Thanks!
Anna

Hi Anna,
The spider in your photo is a type of crab spider, Family Thomisidae, possibly the Elegant Crab Spider, Xysticus elegans. It does not build a web and is often seen running along fences. It ranges from Maine to Georgia and west to Arizona and north to Alberta. It is harmless.

Letter 2 – Crab Spider

Identify this critter please?
I don’t know if I sent you this picture before or not, but I figured I’d try again in case I didn’t the first time. We found this guy motoring across our new carpet. It looked like a spider, but I don’t recall if it had 8 legs or not. It’s almost like a very large tick of some kind. I believe it was around 1/2" in size, give or take a little. We live in Atlanta, GA.
Any ideas?
Dave

Hi Dave,
You have a species of Crab Spider, Family Thomisidae. They do not build webs but wait to ambush their prey, often flies and bees. Many species are found on flowers and they camouflage themselves to look the same color as the flowers. They are sometimes called Flower Spiders for that reason.

Letter 3 – Crab Spider devours Bee

more foodchain
Hi Bugman –
If you can stand one more photo of a crab spider and prey, here it is. I don’t know what kind of bee the spider is sucking the life out of. (Taken at Elkhorn Slough, CA)
Your Fan,
Allison

Hi Allison,
Photos as gorgeous as yours are surely easy on the eyes. It is rare we receive images of this quality. Thank you for the image of a Crab Spider and its luckless Bee.

Letter 4 – Crab Spider ambushes Fiery Skipper

Pale green spider with red stripes
Hello! While in San Antonio, Texas this month I noticed this spider on my parent’s backyard deck. Can you identify it?
Sheila Ryan

Hi Sheila,
This is a Crab Spider. They do not build webs. They are often found on flowers and are also called Flower Spiders. Crab Spiders are in the family Thomisidae. This specimen has captured a Fiery Skipper.

Letter 5 – Crab Spider catches Pipevine Swallowtail

Crab Spider feasts on Pipevine Swallowtail.
Hi again bugman,
I thought I would share with you another image taken the same day as the puddling pipevine swallowtails I sent in, this one of a crab spider enjoying its pipevine swallowtail lunch. Hope you enjoy it!!! Keep up the great work
Michael

Hi Michael,
We have never seen documentation of a Crab Spider with such a huge catch. It is a wonder the spider managed to hold onto that Pipevine Swallowtail. Thanks for sending us another image from the Great Smoky Mountains National Park near Gatlinburg, Tennessee.

Letter 6 – Crab Spider

QUESTION! (Fwd: omg pretty yellow)
HI BUGMAN!
I HAVE A QUESTION ABOUT THIS "BUG"/ARACHNID… PLEASE READ FORWARDED EMAIL TO EXPLAIN. THANK YOU.
Crystal T.
hi, omg so I’m getting gas and I look down and see this face and it totally scares me! …this thing was on my passenger door a couple days ago, then yesterday I thought it was gone but it was on the passenger-side back door… and I had been on the freeway a couple times, all around town etc, and it was still on there. I thought it was dead and stuck to my car – then it was on the back door – and so I wanted to keep it cause it was crazy and while putting it in a film cannister it moved! it’s still alive!!!!! so I have it, not sure what to feed it or if there are any spider-doctors that can fix him?? I tried feeding it a bug but I think all it did was kill it. But afterwards did have lots more energy, like could stand up straight, lol. ok, it’s super alien looking, like a tank. have u seen it b4? really pretty. peter said I should stitch the design on something.
Crystal

Hi Crystal,
We are not sure of the species, but this is a Crab Spider in the family Thomisidae. Though it is missing a few legs, your spider probably won’t have any trouble surviving in the wild. Release it onto some flowering plants.

Ok, thank you! I’ll set him back into the wild. (PS- do u teach @ ACCD?) Crystal

I thought your name sounded familiar.

Art Center, design, 2 terms ago- I ran into you in the Freestyle parking lot not too long ago too. I can’t believe you’re the bugman! That’s so awesome! (I remember you mentioned something about bugs in class though.) I take lots of bug pics, I find them fascinating, so complex and beautiful. There are some I have pix of that I’ve been wondering about too… can I send ’em to you? I can’t believe the coincidence! You could have been some wheat farmer in Montana for all I knew!!!! ^_^
CT

Letter 7 – Crab Spider

yellow spider
I found this spider (unfortunately dead) floating in my pool. I live in Pennsylvania. Can you identify it? It is a very bright yellow-about the size of a dime or slightly smaller.
Wendy

Hi Wendy,
Your drowned Crab Spider is also called a Flower Spider.

Letter 8 – Crab Spider

Spider
Hello,
My father-in-law found this spider in his garden in Sudbury Ontario Canada. Any idea of what it is? Is it harmless?
Thanks
John Sauve

Hi John,
Your father-in-law found a Crab Spider, also known as a Goldenrod Spider or Flower Spider, Misumena vatia. It is harmless except to flying critters that visit the flowers it is usually hiding upon.

Letter 9 – Crab Spider

Flower or Crab Spider… ( Misumena vatia )
Here’s a picture of a Flower or Crab spider ( Misumena vatia ) taken Sept. 4 2005 ( in Southern Ontario, Canada ). At first glance I thought I had some kind of strange albino spider, but after a bit of research online I found out they are just plain ol white and red. You have a wonderful web site, I quite enjoy seeing the different types of critters from around the continent…. some ugly, some beautiful yet all part of natures glory.
TTFN
Todd Nesbitt

Hi Todd,
What a wonderful photograph. We get many questions about this particularly striking color variation of the Crab Spider. Thanks to your image, people will now know how to identify this harmless, beautiful spider.

Letter 10 – Crab Spider catches Fly

Subject: UNUSUAL CRAB SPIDER
Location: Fannie, Arkansas
September 10, 2014 2:43 pm
I know this is a crab spider but the coloration and design are new to me. The spider is white, pink and green with a pink combed effect on the sides, pink area on the abdomen and green on the thorax top. Do you know which crab spider it is?
Signature: Bill Burton

Dear Bill,
What wonderful Food Chain images you have submitted.  We believe that based on this image from BugGuide, your individual is a Whitebanded Crab Spider, Misumenoides formosipes, which is a highly variable species.  Browsing through the images on BugGuide, you can see just how variable the colors and markings are on the Whitebanded Crab Spider.  We have run out of time this morning, and we can’t identify the fly at this time.  Perhaps one of our readers will provide a comment.

Letter 11 – Crab Spider

Subject: Spider
Location: Hartford ky
May 13, 2016 11:11 am
Help me identify this spider
Signature: Jobeth

Dear Jobeth,
This is a harmless Crab Spider in the family Thomisidae, and we believe it most closely resembles one of the Bark Crab Spiders from the genus Bassaniana pictured on BugGuide.

Letter 12 – Crab Spider Courtship

Subject:  Misumena vatia romance
Geographic location of the bug:  SW Virginia, USA
Date: 08/03/2018
Time: 03:23 PM EDT
Your letter to the bugman:  Hello, this lovely yellow crab spider has been hanging out on a metal picnic table all week. I’ve visited and photographed her over several days. Yesterday, she had what I at first took for a baby but now think is a suitor! He’s just a fraction of her size and his coloration is considerably different. I am not sure how he found her, as there are no flowers or yellow colored items close by. You can just see her hiding under the leaf in the 3rd photo. I did not see them interact. What do you think? Also, what are the indentations that make her abdomen look upholstered? Thanks! Love your site!
How you want your letter signed:  Crab spider fan

Dear Crab spider fan,
Though we cannot recall reading about pheromones and Spiders, there must be some means by which a male spider is able to locate a mate.  Your images, though they do not document any actual mating activity, are still a wonderful addition to our Bug Love page.

Letter 13 – Crab Spider

Subject:  Crab spider
Geographic location of the bug:  Killeen, Texas
Date: 11/09/2018
Time: 07:31 AM EDT
Your letter to the bugman:  This looks like a crab spider. Found this beauty on my kitchen counter at O-dark thirty! Startled me but then I spent a good 5 minutes trying to get an adequate picture.
How you want your letter signed:  Michelle in Killeen, Texas

Dear Michelle,
This is indeed a Crab Spider in the family Thomisidae, but we are not certain of the species.  Crab Spiders are not considered dangerous to people.