17 Most Common SPIDERS 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 incredibly interesting creatures and crucial to our environment! Luckily, most spiders are harmless, and they control the insect population.
Today, you will learn about the most common spiders that live in Colorado.
Before we begin, note that the list below is just a fraction of the overall number of spiders found in Colorado. Because of the sheer number of these arachnids, it would be impossible to cover them all. With that being said, I did my best to develop a list of COMMON spiders that are often seen and easily identified.
17 Spiders in Colorado:
#1. Wolf spiders
- Lycosidae
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 spiders that it would be impossible to list them here, especially since most 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! Likewise, some species will make a burrow and then wait inside for dinner to walk by.
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 their venom is not dangerous to humans. Bite symptoms are minimal and may cause itching, swelling, and mild pain.
#2. Cellar Spider
- Pholcidae
Identifying Characteristics:
- Cephalothorax (head) and abdomen are different shades of brown.
- Less than a 1/2-inch (12.7 mm) body, 2-inch (51 mm) 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 spider that is always in the corners of your basement?
Well, it’s most likely a Cellar Spider! These long, thin, and delicate arachnids are commonly found in Colorado in homes and buildings. Whenever I clean my basement with a vacuum, a few of these spiders always seem to get 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 up against their web.
Cellar Spiders are beneficial to have around because they have been known to hunt down and kill venomous spiders.
#3. Crab spiders
Identifying Characteristics:
- On average, females measure 7–11 mm. Males are much smaller and range between lengths of 2–4 mm.
- Colors range widely based on the specific species. However, the most common colors are pink, yellow, white, green, or brown.
The best places to find crab spiders in Colorado are near flowers.
Crab spiders don’t use webs to catch their prey. Instead, they sit and wait inside flowers or other vegetation low to the ground for something to eat. Once a suitable victim comes by, they use their long forelegs to ambush it and make the kill. When insects are in short supply, such as during bad weather, they eat pollen and nectar to avoid starvation.
Lastly, many crab spiders have developed a mutualistic relationship with certain plant species since these spiders feed on and help deter harmful insects. Some plants even release an emission after being attacked that helps attract crab spiders in hopes they eat the intruder.
#4. Daring Jumping Spider
- Phidippus audax
Also called the Bold Jumping Spider.
Identifying Characteristics:
- 4-14 millimeters long, black with white markings on the 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 luckily, 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. Interestingly, when they hunt, these spiders will spin one strand of webbing to use as a lifeline. They do this just in case their jump fails, as the strand of web acts like a bungee cord.
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?
#5. American grass spiders
- Agelenopsis
Identifying Characteristics:
- Both sexes are shades of brownish-black with stripes running from front to back.
- The abdomen is oblong and has two white stripes broken into sections.
- The head has a lighter stripe running down the middle, dividing the two dark stripes.
Grass spiders are one of the fastest spiders in Colorado.
Grass spiders 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.
Fortunately, they are harmless to humans. And they typically stay in their webs unless disturbed.
*The genus Agelenopsis consists of 14 species of grass spiders that live in North America.
#6. Black Widow
Identifying Characteristics:
- Females are 6.35 mm to 9.5 mm 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 spiders in the world. Almost everyone knows the red-shaped hourglass mark that appears on females.
And even though they have highly toxic venom that is 15 times stronger than a rattlesnake, they are not aggressive. 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.
#7. Fishing spiders
- Dolomedes
They’re also known as Fishing Spiders, Raft Spiders, Dock Spiders, or Wharf Spiders.
Identifying Characteristics:
- Both sexes can vary in color; some are brown, black, or cream-colored brown.
- Many species have a striking pale stripe down each side of the body; others have dots down the side of their body.
Fishing spiders are some of the largest spiders in Colorado.
Several different species are found here, and they are all large nocturnal spiders that find their prey around water. You’ll often see them on the docks by a lake during the day.
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, then race across the water to grab it. Most fishing spiders eat insects, but some species can catch small fish.
They can also hunt underwater because of their specialized lungs, which help them breathe while submerged. However, the air in their lungs makes them float, so they need to hold onto a rock or plant, or they will rise to the surface.
#8. Harvestmen (Daddy Longlegs)
- Opiliones
Identifying Characteristics:
- 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!
We often see them in our yard, typically hiding underneath my kid’s playground or on rocks or logs. They are also very social, so you will often find them in large groups.
But even though Harvestmen look just like spiders, these arachnids are technically NOT spiders!
They are in the Order Opiliones, have no venom, lack fangs, and do not bite. In addition, Harvestman can 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 groom by licking. Seriously, you can watch this behavior in the video above!
#9. Spotted Orbweaver
- Neoscona crucifera
Also known as the Hentz Orbweaver, Spotted Orbweaver, and Barn Spider.
Identifying Characteristics:
- Most often, these spiders are golden-orange or rusty-red.
- The legs have alternating dark brown and light brown bands.
- The abdomen is hairy.
These spiders are most often seen in Colorado in late summer and early fall.
Look for their large, orb-shaped web near lights, often constructed on buildings or other man-made objects. During the day, there is often a silken retreat that they retreat to for safety.
If you bother a Spotted Orbweaver, it will bite you in self-defense. But the venom is not dangerous to humans.
#10. Banded Garden Spider
- Argiope trifasciata
Also known as the Banded Orb Weaving Spider.
Identifying Characteristics:
- This species has an oval abdomen and bright body markings. The back of the abdomen is pale yellow with silvery hairs and lateral bands of black stripes. Males are usually paler, sometimes even white.
- Adult females are around 13 to 14.5 mm long.
- Males are considerably smaller, reaching only a third of the females’ length.
The Banded Garden Spider builds an enormous web, typically around 23.6 in (60 cm) in diameter. The web itself is sticky and strong, able to hold very large insects like wasps and grasshoppers. One interesting feature of their webs is the so-called “stabilimentum,” a vertical zigzag pattern made from dense silk. Researchers think this feature is a way to attract insects that the Banded Garden spider eats.
Females usually rest at the center of the web, facing downwards. They face their webs east-to-west to take advantage of the rising and setting sun and hang in the center with their dark underside facing south. All this allows them to gain as much warmth as possible, enabling them to stay active later in the year.
These spiders rarely bite humans in Colorado and are not aggressive.
They may bite in self-defense if handled and bothered, but it’s unlikely that the bite would cause more discomfort than a bee sting.
#11. Zebra Jumping Spider
- Salticus scenicus
Identifying Characteristics:
- Their anterior median eyes are large, which gives them excellent binocular vision.
- The coloration looks like a zebra; black with white stripes.
- Female spiders are 5–9 mm long, while males are 5–6 mm.
Zebra Jumping Spiders are found in Colorado in open, vertical habitats.
Rock faces and tree trunks provide good habitat, but they are also found in close proximity to humans on the walls of buildings and garden fences. You should also check the corners of the windowsills in your house, as they are sometimes found there too. 🙂
Jumping spiders don’t use webs to capture prey but instead use their incredible eyesight for hunting smaller spiders and other invertebrates. Once their victim is sighted, they move slowly toward it until they are close enough to jump on and make the kill, similar to how a cat hunts. Then, just in case they miss the target, they attach a silk thread to a surface so they can climb back up and try again!
To try and impress a potential mate, male Zebra Jumping Spiders will conduct a courtship dance by waving their front legs and pedipalps while also moving their abdomen up and down. A better dance increases the likelihood that the females will want to mate with the male. Males must be VERY careful when approaching the female; if the dance isn’t good enough, they risk being eaten.
#12. Northern Yellow Sac Spider
- Cheiracanthium mildei
Identifying Characteristics:
- The body is typically tan or pale green. The mouthparts are darker brown.
- Adults are typically 7–10 mm (0.3–0.4 in) in size.
Northern Yellow Sac Spiders are NOT NATIVE to Colorado.
They are originally from Europe and North Africa and were introduced long ago by English colonists. But since they have been here so long, these spiders are now common, especially INSIDE homes.
Unfortunately, Northern Yellow Sac Spiders will bite a human without hesitation. In fact, they have been observed crawling across the skin and biting for no particular reason. Luckily, bites from this species are relatively painless and medically insignificant. But bites from its cousin, the Yellow Sac Spider (Cheiracanthium inclusum), are MUCH more serious.
#13. Cat-faced Orbweaver
- Araneus gemmoides
Also known as the Jewel Spider and Cat-faced Spider.
Identifying Characteristics:
- They are found in many different colors.
- Identified by the two horn-shaped growths found on the large abdomen.
The Cat-faced Orbweaver is a common spider in Colorado.
Look for their webs near lights, closed spaces, and on the sides of buildings.
After laying a single egg sac filled with hundreds of babies, the female dies a few days later. As the spiderlings hatch from the egg sac, many of them will eat their siblings as their first meal!
The baby spiders that survive predation from their brothers and sisters have an interesting way of traveling to new locations. The spiderlings can float many miles away by riding strands of silk that are blown in the wind!
#14. Texas Brown Tarantula
- Aphonopelma hentzi
Also known as the Oklahoma Brown Tarantula or Missouri Tarantula.
Identifying Characteristics:
- 2-inch body length and 4-inch leg span.
- The head is a lighter brown with a dark brown abdomen, but shades vary.
- Legs, abdomen, and fangs are covered with fine hairs.
This species is one of the biggest spiders in Colorado!
Look for Texas Brown Tarantulas in dry, arid environments, under stones, logs, and underground burrows. They can make their own burrow but commonly use unoccupied animal dens.
Texas Brown Tarantulas Range Map
Even though the Brown Tarantula is large, it is non-aggressive and typically runs 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 of their 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 and are 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.
#15. False Black Widow
- Steatoda grossa
Also known as the False Widow, Cupboard Spider, or Dark Comb-footed Spider.
Identifying Characteristics:
- Females measure 6-10.5 mm (0.23-0.41 in). Males are similar in size but thinner.
- They’re dark brown with a round, bulbous abdomen.
- The female abdomen is more rounded than the male’s.
As the name suggests, many people commonly confuse this spider in Colorado with the venomous Black Widow. But luckily, this species is not dangerous, and it’s easy to differentiate because they don’t have the ominous red hourglass on the abdomen.
False Black Widows are considered cosmopolitan species, which means they are commonly found in and around homes. They prefer dark areas, such as under furniture or in basement corners. These spiders normally don’t bite unless they are accidentally pinched or squeezed. But if you are bitten, they may potentially cause you some harm, unlike most spiders. Common symptoms include blistering, muscle spasms, pain, fever, sweating, and discomfort lasting for several days.
Here are two facts about False Black Widows that I found fascinating!
- Females can live up to six years! Males live shorter but still up to 1.5 years.
- As long as they have access to water, they can live several MONTHS without food.
#16. Johnson’s Jumping Spider
- Phidippus johnsoni
Also known as the Red-backed Jumping Spider.
Identifying Characteristics:
- Adults are about 10 mm long.
- Both males and females have a red abdomen. The rest of the body is mostly black.
- The chelicerae (mouthparts) are a bright teal color.
This species is one of the largest and most common jumping spiders in Colorado! Johnson’s Jumping Spiders typically construct silken nests on the ground that are found underneath rocks and wood.
They prey on almost any insect that is smaller than them. But interestingly, other spiders make up a large part of their diet. Cannibalism is also common in females as they dine on smaller males.
And the most interesting fact about Johnson’s Jumping Spiders is that one was sent to space in 2012! Nicknamed “Spidernaut,” the spider traveled to space for 100 days to see if jumping spiders could adapt to the microgravity in space and then transition back to Earth. Read all about the experiment here. 🙂
#17. Hobo Spider
- Eratigena agrestis
Identifying Characteristics:
- Both sexes are between 7-14mm.
- Light brown or tan in color with two darker bands extending back.
- There is usually a thin dark line down the center of the head region.
- Correctly identifying this spider is difficult because individuals vary greatly in appearance.
The Hobo Spider got its name because it’s often found along railroad tracks. It is also referred to as the “aggressive house spider,” but this name is misleading as it does not naturally live indoors. In addition, it’s also not aggressive unless catching its prey or when trapped against a person’s skin.
Hobo Spider Range Map
You can find Hobo Spider webs by entrances, under rocks, or among piles of debris. But they are also found in other places close to the ground with holes and cracks, such as rock retaining walls, construction supplies beneath the debris, and building foundations. In addition, adult males sometimes wander into houses.
Learn more about animals found in Colorado!
-
20 Common SNAKES That Live in Colorado! (ID Guide)
-
35 Common Bird Species Found in Colorado! (With Photos)
-
18 INSECTS You Can Find in Colorado
Do you need more help identifying a spider you found in Colorado?
Try this field guide!
Which of these spiders have you seen in Colorado?
Leave a comment below!
