The 19 Common Spiders Found in Colorado! (ID Guide)
“What kinds of spiders can you find in Colorado?“
Many people are terrified of spiders and find them extremely creepy. This is unfortunate because they are crucial to our environment and are incredibly interesting creatures!
Luckily, most spiders are harmless, and they control the insect population. In fact, without spiders, our food supply would be in jeopardy!
Today, you are going to learn about 19 spiders that live in Colorado.
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Before we begin, note that the list below is just a fraction of the overall spiders in Colorado. Because of the sheer number of these arachnids, it would be impossible to cover them all. For example, some estimates claim there are over 50,000 species on the planet!
With that being said, I did my best to develop a list of COMMON spiders that are often seen and easily identified.
#1. Wolf Spider
- Both sexes look alike and range from 0.4 to 1.4 inches, not including their legs.
- 8 eyes total – the top row has 2 medium-sized eyes, 2 large eyes in the middle row, and the bottom row has 4 smaller eyes.
Wolf Spiders are one of the most recognizable spiders in Colorado!
They are found everywhere and in almost any habitat. I know that I see them often when flipping over rocks or logs. Unfortunately, there are so many individual species of Wolf Spider that it would be impossible to list them here, especially since most of them look very similar.
Wolf Spider Range Map
Interestingly, Wolf Spiders do not make webs to catch their prey. Instead, they wait for an insect to walk by and then chase it down! Some Wolf Spiders will make a burrow and then wait inside for dinner to walk by. Most Wolf Spiders wander without a permanent home, and they always live and hunt alone.
When it comes to arachnids, Wolf Spiders have incredible eyesight. They also have retroreflective tissue in their eyes, which produces a glow if you flash light at their faces.
Wolf Spiders will bite if provoked, but they do not always inject venom. Therefore, they are not considered dangerous to humans. Bite symptoms are minimal and may cause itching, swelling, and mild pain.
#2. Cellar Spider
- Cephalothorax (head) and abdomen are different shades of brown.
- Less than a 1/2-inch body, 2-inch long legs, and the body is the shape of a peanut.
- Some species have 8 eyes, while others only have 6 eyes.
You know that one spider that always seems to be in the corner of your basement?
Well, it’s most likely the Cellar Spider! These long, thin, and delicate arachnids are commonly found in Colorado in homes and buildings. Every time I clean my basement with a vacuum, a few of these spiders end up getting sucked inside.
Cellar Spider Range Map
Cellar Spiders do something exciting when their web is disturbed by touch or has entangled large prey. They start vibrating rapidly, which has led to them sometimes being called “vibrating spiders.” They do this behavior to hide from predators or increase the chance of catching an insect that brushed their web to entangle the prey further.
Cellar Spiders are beneficial to have around because they have been known to hunt down and kill venomous spiders.
#3. Black Widow
- Females are 1/4 to 3/8 inches long.
- Shiny black with a distinctive red hourglass-shaped mark. A row of red spots is sometimes visible above.
- Males are half the size of females but have longer legs.
Black Widows are the most venomous spiders in Colorado!
In addition, they are probably the most popular and recognizable spider in the world. Almost everyone can recognize the red-shaped hourglass mark that appears on the females.
Black Widow Range Map
But here’s the good news:
Even though they have highly toxic venom, 15 times stronger than a rattlesnake, they are not aggressive animals. The Black Widow only bites defensively if the web is disturbed, and they RARELY bite humans.
But, if you are one of the few unlucky people who are bitten each year, you should know that the venom affects your nervous system. Some people are only slightly affected by it, but many have a severe response. If you are bitten, the bite requires medical attention, and the neurotoxic venom can be fatal to small children if untreated.
Black Widows prefer dimly lit locations, dark corners in a basement, closets, and cluttered areas.
The best places to look for them include overhanging ledges, under benches or stones, near entrances to abandoned rodent burrows, or around outbuildings. They don’t like moisture and prefer dry areas.
#4. Trapdoor Spider
- Both sexes range from dark brownish-black or a lighter reddish-brown,
- Body is around 1 inch in length, and some can grow to 1.6 inches in length.
- Head is shiny and hard, and their abdomen is usually brighter and hairy.
Trapdoor Spiders do not create webs like most other spiders in Colorado.
Instead, they build underground tunnels made of silk material and secure their entrance with a door that can be closed with a hinge. As you can see, this is how they get the name “Trapdoor.”
Trapdoor Spider Range Map
Trapdoor Spiders are actually fast runners and have two large fangs to catch prey. So once the prey is near the tunnel, it’s in big trouble because the Trapdoor Spider will get it.
Luckily, Trapdoor Spiders are not aggressive and usually run underground before any human can get close to them.
In the rare cases in which a bite occurs, they are only mildly painful and are not dangerous.
#5. European Garden Spider
- Araneus diadematus
- Colors vary from light yellow to dark grey; the head has thick long hair and looks furry.
- Tiny hairs cover its large abdomen, and spiky hairs cover its legs. The female abdomen is more bulbous shaped than the males.
- White markings on the abdomen with four or more segments that form a cross.
- Also known as the Cross Spider, Diadem Spider, Orangie, Pumpkin Spider, and Crowned Orb Weaver.
European Garden Spiders have eight eyes, but it actually looks like they have six eyes. That’s because they’re so small, they can-not be seen with the naked eye.
European Garden Spider Range Map
The first web the European Garden Spider makes in its lifetime is perfectly created.
The weird thing is…
As time goes on and they build more and more webs, they begin to have more flaws and get sloppy. I guess practice doesn’t always make perfect!
Once they build their web, they sit right in the middle with their head pointing down to the ground waiting for prey. If they should leave their web, they attach themselves to a single trigger line to feel the vibrations of prey that gets attached. It’s like a security system and a dinner bell all in one.
#6. Running Crab Spider
- Brown or gray with little other markings and are very flat looking.
- The second pair of legs from the front is longer than all the other legs.
They can be found in pastures or forests by a water source. But, unfortunately, they also wander into human structures.
Running Crab Spiders only build webs for their egg sac and don’t use them to catch prey. Instead, they are hunting spiders that rely on their camouflage to hide. They also can run very fast to chase and track down prey.
Running Crab Spider Range Map
Interestingly, Running Crab Spiders can lose a leg and then grow a new one.
Their bite can be painful with some swelling. And sometimes, it can cause a headache, inflammation, or prolonged pain or lead to vomiting or irregular pulse rate, though this is rare. They are considered low risk.
#7. Daring Jumping Spider
- Phidippus audax
- 4-14 millimeters long, black with white markings on abdomen and legs.
- Eight eyes, but two are much bigger. Green metallic fangs.
- Sometimes they have orange marks on the abdomen when they are younger. As they get older, they turn white.
Daring Jumping Spiders can jump up to 50 times their body length.
But here’s the good news:
They are tiny spiders. Could you imagine if they were the size of a Tarantula?
Daring Jumpers are hunting spiders that like open areas to stalk and chase down prey. They only make webs to protect their egg sac or to rest in at night. They spin just one strand of webbing to use as a lifeline they need to escape predators. They also do this just in case their jump fails, which serves like a bungee cord.
Daring Jumping Range Map
Daring Jumpers are common in fields and grassy areas. You will sometimes find them on fences or walls of outside structures because they like flat surfaces, and they point downward to make it easier on themselves to catch prey. Why work harder when you could work smarter?
They are afraid of humans and run away most of the time. But if you are bitten, it will be painful with lots of swelling, followed by fever, chills, nausea, vomiting, and headaches. This tiny spider packs quite a punch, but it is in the low-risk category, so don’t worry too much!
#8. Texas Brown Tarantula
- Aphonopelma hentzi
- 2-inch body length and 4-inch leg span.
- The head is a lighter brown with a dark brown abdomen, but shades can vary.
- Legs, abdomen, and fangs are covered with fine hairs.
- Also known as the Oklahoma Brown Tarantula or Missouri Tarantula.
The Texas Brown Tarantula is one of the biggest spiders in Colorado!
Look for them in dry, arid environments, under stones, logs, and underground burrows. Interestingly, they can make their own burrow but commonly use unoccupied animal dens.
Texas Brown Tarantulas Range Map
Even though the Texas Brown Tarantula is large, they are non-aggressive and typically run away from humans. But if they feel threatened, they will stand on their hind legs and put up their front legs to appear larger to scare away a threat.
If you are bitten, which is EXTREMELY rare, the bite is quite painful because of its large fangs. But luckily, the venom is harmless to humans and doesn’t cause additional pain.
To help them be more successful hunters, Texas Brown Tarantulas will put silk at the entrance to the burrow. This acts like a security alarm, where they can feel the vibration and know that dinner is waiting!
Females have been known to live up to 40 years, one of the longest living spiders in Colorado.
On the other hand, males drew the short straw and rarely live past a year after they’ve matured.
#9. Furrow Spider
- Larinioides cornutus
- Colors can vary from black, grey and shades of red.
- The abdomen is a very large smooth, oval shape.
- Lighter-shaded arrow markings pointing towards their head on the abdomen. Legs have a similar arrow pattern.
- Also known as Furrow Orb Spider or the Foliate Spider.
Furrow Spiders are found in Colorado in moist places near a water source in the grass or shrubbery. These arachnids don’t mind being by human structures either, like porches or corners of houses.
Furrow Spider Range Map
Did you know that spiders can’t hear? Furrow Spiders, like many other spiders, actually use the hairs on their legs to sense sound.
Like other orb weaver spiders in Colorado, these spiders make a new web every night. The reason for this is that they eat their web every single morning!
They rarely bite, but if bitten, you will only have mild pain and little discomfort.
#10. Banana Spider
- Trichonephila clavipes
- Reddish-brown and yellow coloring and a yellow oblong-shaped abdomen (like a banana),
- Long, straight, yellow legs, with black bands covered with hairs.
- The head is small and grayish-white with black dots that kind of look like a skull.
Banana Spiders are found in woods and forests in Colorado.
Look for their asymmetrical webs made of golden-colored silk that can be up to 6 feet in diameter!
Banana Spider Range Map
Female Banana Spiders are much larger than males, like many other common spiders.
But luckily for the male, the female does NOT eat them after they mate.
Banana Spiders silk is unique because they produce seven different types. The golden-colored silk is also very strong, and studies have shown its potential for use in surgeries to help the nervous system.
#11. American Grass Spider
- Both sexes are shades of brownish-black with a pattern of stripes running from front to back.
- The abdomen is oblong and has two white stripes broken into sections.
- The head has a lighter strip running down the middle, dividing the two dark stripes.
American Grass Spiders are one of the fastest running spiders in Colorado.
American Grass Spider Range Map
American Grass Spider are funnel weavers, which means they weave a funnel on one edge of their web. Their webs are not sticky, like other spiders. But once the silk is triggered, they use their speed to run quickly to get their prey.
The Grass Spiders will typically stay in their web unless disturbed. Fortunately, they are harmless to humans.
#12. Black and Yellow Garden Spider
- Argiope aurantia
- Both sexes have light-gray heads with white or silver.
- The body is around 1 inch long. The abdomen has a wide black mark in the center and sides and is covered with yellow patches.
- The males are around 1/4 of an inch in length, not counting legs.
- Legs start off orange or dark yellow close to their body and mostly black towards the ends.
- Also known as the Yellow Garden Spider.
The Black and Yellow Garden Spider is one of the most recognizable in Colorado!
They make beautiful webs with a distinct circular shape that can be up to 2 feet in diameter. Look for them in sunny, open fields or gardens, as the name suggests.
Black and Yellow Garden Spider Range Map
Black and Yellow Garden Spiders are among the species that make their webs in the daytime.
Look for a thick zigzag of silk in the center of the web, called the stabilimentum, which helps camouflage the spider while they sit there. It’s thought the zigzag mark helps to deter larger predators from running into it and destroying it. I know I’d immediately stop in my tracks if I saw one!
They’re also able to move their web vigorously while remaining in the center of it. They do this to prevent predators from taking a good part of the web, and it helps entangle an insect before it gets loose and falls off.
Black and Yellow Garden Spiders are not aggressive, but they will bite if grabbed or provoked. However, the bite is harmless to humans, and the worse it can do is feel like a bee sting.
#13. Red Spotted Ant Mimic Spider
- Castianeira descripta
- Both sexes are black with red or orange markings on their back.
- Females are larger than males.
Red-spotted Ant Mimic Spiders are sometimes mistaken for Black Widows! The reason for the confusion is because of the red and black coloring on both species. Luckily, with a little training, it’s easy to tell the difference.
The best place to look for them is under rocks, but it’s not uncommon for one to make it into your home.
Red Spotted Ant Mimic Spider Range Map
The Red-spotted Ant Mimic Spider gets its name from its weird behavior. They often walk with their two front legs held up in the air while twitching them, which gives it the appearance of being a six-legged ant with antennae. It does this to mimic ants, which allows them to get close enough to prey to attack!
These aggressive spiders mostly target ants or small insects and leave pets and humans alone. If you are bitten, you may have swelling and redness at the site. People with allergies should be more cautious.
#14. Fishing Spider
- Both sexes can vary in color; some are brown, black, or brown cream-colored.
- Many species have a striking pale stripe down each side of the body; others have dots down the side of their body.
- They’re also known as Fishing Spiders, Raft Spiders, Dock Spiders, or Wharf Spiders.
Fishing Spiders are one of the largest spiders in Colorado.
There are several species of Fishing Spiders in Colorado. They are all semiaquatic, except for the D.albineus, which lives in trees.
Fishing Spiders are large nocturnal hunter spiders that find their prey around water. Many times you’ll see them on the docks by a lake during the day.
Fishing Spider Range Map
These arachnids have special short velvet-like hairs that don’t get wet, allowing them to stand or run on the water. They wait for prey to make a ripple and then race across the water to grab it. Most Fishing Spider species eat insects, but some species can catch small fish.
They can also climb underwater because of their special lungs, which help them breathe while submerged. However, this trapped air makes them float, so they need to hold onto a rock or plant, or they will just float up to the surface.
#15. Spitting Spider
- Light brown with dark brown spots all over the head and abdomen, and the dome-shaped head is larger than the abdomen.
- Legs are light brown with several dark bands.
- Males are only slightly smaller than females.
Spitting Spiders are the only spiders in Colorado that spit web to catch their prey.
They prefer cool and dry places to live. You can find them under stones outside houses or sometimes inside your home in the basement.
Spitting Spider Range Map
Most spiders use their silk just to make webs. However, Spitting Spiders have two silk glands by their fang glands, so they actually spit the silk-covered venom at their prey to paralyze it. Sort of sounds like this is where Spider-Man got his inspiration!
Luckily, the Spitting Spider is harmless to humans and pets. They’d never try to attack, and their fangs are not strong enough to penetrate human skin.
Watch how quickly and efficiently a Spitting Spider attacks a Common House Spider!
#16. Mouse Spider
- Scotophaeus blackwalli
- Medium-sized, dark brown cephalothorax (head).
- The abdomen is brownish-grey with hairs like a shiny mouse.
- Legs are lighter brown with thick hairs all over.
- Also known as the Ground Spider.
These spiders are found in all over Colorado. Look for them on trees under bark and inside houses.
Mouse Spiders look like their body is lying on the ground as they walk. They move quickly and often stop suddenly and then start moving again, much like a mouse moves.
Mouse Spider Range Map
This is a nocturnal ground spider, and they do not spin webs to catch prey. Instead, they roam around looking for insects to prey on. Interestingly, they also eat dead insects and dead spiders.
Mouse Spiders produce sticky glue-like silk that they use to immobilize prey. Because of this adaptation, they can prey on larger insects, including larger spiders. Luckily, their venom is weak, and they are harmless to humans.
#17. Common House Spider
- Parasteatoda tepidariorum
- Both sexes can appear anywhere from nearly black to a variety of colors.
- They sometimes have patterns of different colors on their body.
- Females are larger than males, but females have a bulb-like abdomen, and males do not.
These spiders are found in Colorado NEAR PEOPLE!
I know that I always find them in my garage! It always surprises me how small Common House Spiders really are, as they are generally only between 5 and 6 millimeters (0.20 and 0.24 in) long.
Common House Spider Range Map
Even though there are probably a few of them in your house right now, you shouldn’t hate Common House Spiders. They are actually helpful because they feed on small insects and pests in your houses like flies, ants, and mosquitos.
Even though they are relatively docile, bites do occur mostly due to their close proximity to humans. But have no fear, their venom is not dangerous in the least.
#18. Bowl and Doily Spider
- Frontinella pyramitela
- Small, with a large, round and shiny abdomen that is dark brown or black along the top with thick white vertical lines on the sides
- White markings on the bottom of the abdomen. But the color can differ between spiders – some are dark yellow and some have no color at all.
- Head is reddish-brown, legs are lighter brown, thin and long.
Have you ever seen patches of web in shrubbery or hanging low in the woods?
If so, it was probably the web from the Bowl and Doily Spider. They are best known for their horizontal sheet webs that resemble a bowl, which is found in weedy fields or shrubs in all types of habitats.
Bowl and Doily Spider Range Map
Bowl and Doily Spiders build their sheet web between twigs and are only a few inches in diameter. The spider sits on the bottom of the bowl and waits for prey on the underside. Being on the bottom provides the spider safety but also allows a surprise attack! You see, they can actually bite their prey directly through the web!
Males seldomly build webs, but they are known to cohabitate with females for long periods of time in their web. As a result, it is common for multiple males to mate with the female, which causes sperm competition.
#19. Harvestmen Spider (Daddy Longlegs)
- Colors vary; most are dull brown or dull gray, but some may be yellowish, greenish-brown, or reddish.
- Look for a dark blackish streak down the middle and sides.
- Single body region, only two eyes that do not see well.
“Daddy Longlegs” might be the most recognizable spider in Colorado!
I know we see them often in our yard, typically hiding underneath my kid’s playground or on rocks or logs in the woods. They are also very social so you will many times find them in large groups.
But here’s the crazy thing:
Harvestmen Spider Range Map
Even though Harvestmen look just like spiders, these arachnids are technically NOT spiders! They are in the Order Opiliones and have no venom, lack fangs, and do not bite.
In addition, Daddy Longlegs can actually swallow solid food, which allows them to eat small insects, fungi, dead organisms, bird dung, and other fecal matter. This differs from spiders that only eat their prey after turning them into a liquid.
As you might guess by their nickname, their legs play a vital part in their life. They use their legs for breathing, walking, smelling, and capturing prey. Males have longer legs than females, which they will groom by licking with their mouthparts. Seriously, you can watch this behavior below!
Do you need additional help identifying a spider?
Try this field guide!
Which of these common spiders have you seen in Colorado?
Leave a comment below!