Among the many spiders in Colorado are a few dangerous ones, a few scary-looking ones, and many others that are a downright blessing to the ecology.
This article will help you identify many of them and hopefully set your mind at ease about any particular arachnid you encounter.
Black widow spiders in Colorado.
Black widow spiders in Colorado are the easiest spider to identify. But, unfortunately, black widow spiders are also the most horrifying spider to identify up close and personal. The fear of the hourglass-shaped spider’s bite is world-renowned throughout the temperate regains of the entire world.
In many articles on black widow spiders in Colorado, the author suggests that the reports of their venom and the inherent dangers of encountering black widow spiders are deemed “over-rated.”
That’s not true. Indeed, the black widow spider is nasty and potentially fatal to young and elderly humans. Therefore, any helpful article will recommend they be avoided, and those who live where black widow spiders reside can identify and avoid them.
The black widow spider in North America can also be red (Latrodectus bishopi ) or brown (Latrodectus geometricus). Despite their color, female black widows have dark-colored and easily identified reddish hourglass markings on the central underside. Only the female has a bite hazardous to humans.
Black widow spiders in Colorado: Fascinating facts.
A study conducted in the 1950s found that 80% of black widow spider bites happened to men, most of whom were bit on the penis. Ouch! Why?
As reported in IFLScience.com, “Most of the black widow bites that were reported happened in outhouses.
“So black widow spiders enjoy dark, low-to-the-ground sort of places. They especially love to make their cobwebs between two objects,” she explained, adding that bugs and flies love the stink of outhouses and made their home in the privvy bowls.
“So putting your web there is excellent. So imagine this. It’s the 1950s. You’re a dude. You need to go number two. You make your way out to the outhouse. You sit down, and your junk hangs there.”
“And as it does, it hits the cobweb. And the usually non-aggressive black widow instinctually runs over and bites down on the new creature that has landed on its web.”
Since bathrooms began moving indoors, the problem (disproportionate targeting of men and penises) seems to have gone away. Their bites today are rarely fatal, with the majority resolving without treatment and others being treatable in hospitals. “
Need any more reasons to fear black widow spiders?
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Positively identifying brown recluse spiders in Colorado.
Identifying brown recluse spiders in Colorado begins by considering where you have found the spider in question.
Brown recluse spiders (Loxosceles reclusa) are commonly found in the Southern Central and Midwestern states. Sure, you could be looking at a traveler who has hitched a ride north, further east, or west. However, that spider is well outside its native territory. Indeed, it will never procreate enough to become an actual problem on the level of an infestation.
Traveling spiders (like the Hobo spider) sometimes enter and inhabit new regions. But the brown recluse spider won’t survive such migrations.
Brown recluse spiders: The eyes have it!
Adult brown recluse spiders in Colorado are about the size of an American quarter (nearly an inch). Surprisingly, they are brown or tannish in color. Their abdomens and legs have no bands, mottling, stripes, or visible spines.
Don’t forget that they neither play violins or fiddles nor possess images of such musical instruments in markings or tattoos.
What sets the brown recluse spider in Colorado apart from most other spiders you will encounter? First, they only have six eyes!
Retake a look at the closeup photo above. You’ll see that brown recluse spiders have a semi-circular eye arrangement (three sets of two), but most spiders have eight eyes.
Okay, I’ll admit that counting the number of tiny eyes on an inch-long spider is difficult. And no one has a magnifying glass at home, which is readily available anymore. So grab that iPhone, snap a photo, and zoom in on the spider’s face.
When you get to the hospital, you can use the picture to help diagnose why you are shrieking in agony and convulsing on their table. Just kidding, we’ll talk more about the bite of brown recluse spiders later.
The slanting legs of the brown recluse spider in Colorado.
Brown recluse spiders are rather plain with uniformly tan or brown abdomens, but their legs (which lack spines, as noted above) are covered in fine hairs. In addition, these legs are slanted (hence the scientific name Loxosceles, meaning slanted legs in Latin).
Brown recluse soldiers in Colorado do not walk funny; instead, the rest with their legs slanted.
Barn funnel weavers in Colorado.
Barn Funnel Weaver spiders (Tegenaria domestica) are a species that is widespread across the United States, from outbuildings and barns to crevices in door frames and cracks of rock faces. It can often be found hidden beneath boards or even underneath rocks!
Barn funnel weaver spider: Identification.
Female Barn funnel weavers in Colorado average a meager half an inch in length, and male counterparts merely one-third of an inch. As a result, their cephalothorax is colored with red-brown hues, adorned by light yellow hairs and two subtle gray streaks running along its length. Meanwhile, the abdomen varies from pink to pale flesh tints featuring grey to black blotches. On top of that, their legs are spiny appendages topped off with faint grey stripes at the end of each femur.
Much like the webs of grass spiders, these webs are usually smaller in size, and the retreats for these spinners lie within the web sheet instead of being found to one side.
The Triangulate cobweb spiders in Colorado: Identification.
At first glance, this tiny Triangulate cobweb spider in Colorado might be easily overlooked since it tends to build its cobwebs in dark corners of households and basements. Measuring only 1/8 – ¼ inch long, the cephalothorax is brownish-orange, while each of its yellow legs contains darker sections at their tips.
The abdomen has a finely pubescent texture with shades of brown and white, triangular spots along the mid-dorsal part, and irregular markings adorn the lateral area.
Triangulate cobweb spider: Habitat.
The Triangulate cobweb spider is found in abundance locally around houses in North America, spreading rapidly since its introduction. Although rare in South America, evidence of sightings has also been recorded there.
You’ll often find these brush-footed spiders (Theridiidae family) in urban environments, near human constructions, tucked away on walls’ dark corners, around windowsills, and beneath eaves. They weave irregular webs that they hang from as a trap for their victims, using the sharp bristles of their hind legs to ensnare them with sticky silk before finally biting down when the prey is stilled.
The Triangulate cobweb spider in Colorado is a predator to be wary of, as it can often be found close to the brown recluse and common house spiders. Hiding out inside closets, crevices, and other nooks, this arachnid has been known to feast on ants, ticks, and pillbugs – not to mention its kind!
Zebra Jumping spiders in Colorado: Description.
Female Zebra jumping spiders (Salticus scenicus) range in size from .2 to .35 inches; males are smaller, with the largest being about .25 inches. The males, who often struggle with the female and other suitors, have larger jaws than the females.
And, of course, there are the eyes of the Zebra spider. It has four pairs of eyes, two of which (the anterior median eyes) are almost comically large and sit next to each other on the spider’s flat face. The larger eyes give the Zebra jumping sider binocular vision.
Zebra spiders are known for their black hairs with white hairs that form zebra-like stripes.
Zebra spiders: Habitat.
Zebra are found across Europe, North America, and North Asia.
Outdoors they are found in open habitats such as the faces of rocks, rocky beaches, and the trunks of trees.
Zebra jumping spiders do not create webs to catch their prey. Instead, jumping spiders build “retreats.” Retreats are more loosely woven and serve only to protect the spider and house the female and her eggs.
You will find Zebra jumping spider retreats inside your home under chairs and tables, near windows and doors, or tucked between cracks in wood flooring. Outside, Zebra jumping spiders build their retreats on leaves, tight spaces in wood piles, and in crevices in tree bark.
Jumping spiders have poor night vision and spend the night in their retreats. During the day, they are attracted to sunlit areas inside your home (windows are a favorite as other insects will be drawn to them). Outside, you’ll find jumping spiders running everywhere the sun has brightened (pool decks, fences, patio stones, etc.).
Aside from the odd, likely trapped against its will, window-dwelling Zerba jumping spider jumping spiders are not inclined to live inside your home. Indeed, you will never find you have an infestation of jumping spiders.
Bold jumping spiders in Colorado.
Bold Jumping spiders (Phidippus audax) are a member of the genus Phidippus. Notable features include their big eyes and iridescent chelicerae. All jumping spiders employ stereoscopic vision for hunting prey and communicating with potential partners during mating rituals.
Native to North America yet found in Hawaii, the Nicobar Islands, the Azores, and The Netherlands; these black arachnids are identifiable by the white triangle on their abdomen.
Bold Jumping Spiders in Colorado are solitary hunters that rely on their impressive eyesight to track, capture and devour a range of arthropods, including caterpillars, dragonflies, and grasshoppers. It is common in agricultural areas and has also been studied to ascertain its influence on crop pest numbers. In contrast with most spiders constructing webs for prey-catching purposes, bold jumping actively hunts down their victims!
These spiders can be found in temperate climates in various terrestrial habitats, including grasslands, chaparrals, open woodlands, and agricultural fields. The bold Jumping spider is one of the most commonly occurring spider species within its range and is often found near humans. Bites from Phidippus audax in Colorado are rare but may occur if they feel threatened or are mishandled. They are generally harmless, but victims must wash the area with water and mild soap if bitten.
Bold jumping spider: Description.
Bold jumping spiders in Colorado are unmistakable creatures – females reach up to .6 inches in body length, whereas the males strand an oval abdomen, making them easy to spot!
The Bold jumping spider in Colorado can easily be identified by its white triangular mark in the center of its back, accompanied by two more minor spots beneath it. Its upper abdomen is also marked with a distinct lateral white band that distinguishes this species. However, what stands out most about these creatures are their tremendous and powerful legs: males have distinctive fringes on their legs and pedipalp, while females boast a longer fourth pair of legs than those found on male specimens.
The chelicerae of adult males glisten emerald green and boast spectacular markings and tufts of fur over the eyes, whereas spiderlings’ chelicerae display orange hues that gradually lighten with age. Furthermore, Bold jumping spiders come in various sizes and colors depending on their habitat location.
The Apache jumping spider (Phidippus apacheanus) is a jumping spider in the family of Salticidae. It is found in the United States, Mexico, and Cuba.
Apache jumping spiders in Colorado: Identification.
The colorful and impressive Apache jumping spider in Colorado is quite large; the petite males measure a minuscule 1/10 of an inch, while female counterparts can exceed 8/10 of an inch. Most are black with orange, red, or yellow accents on top and feature a distinctive black line across their abdomen and iridescent green chelicerae.
The Spotted Orb Weaver in Colorado.
The Spotted orb weaver (Neoscona crucifera) is a captivating arachnid in the Araneidae family, found from Maine to Florida on the East Coast and Minnesota in Midwest America, reaching down to Arizona and southern California.
This orb-weaver spider also has two common names: Hentz orb weaver or barn spider – although this latter name can sometimes be misused for another type of creature called Araneus cavaticus.
Spotted orb weaver: Description.
Typically active at night, female Spotted orb weaver spiders in Colorado may switch to a daily schedule in the fall. Females range between 0.35–0.75 inches long, while males are smaller in size.
The top of their abdomens is brown and hairy with alternating light and dark brown stripes on their legs; meanwhile, the underside displays two white spots against a black background.
The Spotted orb weaver in Colorado boasts a wide array of colors and patterns but most typically displays rusty red or golden orange. Their webs are incredibly giant in circumference, often erected on artificial structures like buildings several feet above the ground level, particularly around outdoor lights.
Wolf spiders (Lycosidae), such as the Carolina wolf spider (Hogna carolinensis), are robust and agile hunters who do not spin webs but chase down their prey.
The Carolina wolf spider.
The Hogna carolinensis, or Carolina wolf spider, is one of the largest species of wolf spiders in Virginia and the eastern United States. With a body length of up to 1.5 inches and an impressive leg span extending up to 3 inches, this robust hunter doesn’t need webs for survival – its agility allows it to chase down its prey simply.
These wolf spiders in Virginia are typically brown or grey, with a mottled or striped pattern on their abdomen. They reside in various habitats, including forests, grasslands, and urban areas. The Carolina wolf spider in Colorado is not dangerous, as it will only bite if it feels threatened. However, their large size and sometimes rapid movements can intimidate some people.
Parson spiders: Identification.
Herpyllus ecclesiasticus, or the “parson spider,” is an aptly named arachnid distinguished by its abundant black and gray hairs that cover its body. Its chestnut-brown exoskeleton is visible on its legs, while a small white spot lies just above the spinnerets – resembling the cravat worn in centuries past. These spiders are tiny; females measure 1/3 to 1/5 inches long, whereas males average 6 millimeters.
Parson spiders in Colorado, unlike their web-building counterparts, orb weavers, are ground spiders that seek out prey and hunt on the prowl. Usually active at night and taking shelter in leaves or underneath stones during the day, seventeen different genera can be found across America.
However, parson spiders in Colorado are perhaps the most commonly encountered of all these species as they look for warm areas to hibernate come wintertime – often entering human dwellings!
Woodlouse spider: Description.
The Woodlouse spider has only six eyes arranged in an oval pattern. They have an orangish-dark brown cephalothorax and a yellowish-brown abdomen. The jaws of Woodlouse spiders are conspicuously large for a spider its size, slanted forward, and quite thick.
Female Woodlouse spiders in Colorado can reach body lengths of .6 inches, with males usually under .5 inches.
All Woodlouse spiders have gleaming bodies.
The woodlouse spider is often mistaken for the brown recluse spider
The Woodlouse spider has a familiar and scientific name that tells you everything you need to know about it. The Woodlouse spider in Colorado eats Woodlice. The scientific name (Dysdera crocata) suggests its color, saffron.
Despite this, the Woodlouse spider has many other names like the slater spider, pillbug hunter, sow bug hunter, and sow bug killer. All these names relate directly to the prey it fancies most.
Striped fishing spiders in Colorado: Description.
Striped fishing spiders (Dolomedes scriptus) are often called “writing” signing spiders because of the marking on their backs.
The striped fishing spider In Colorado is among the eight species in the genus Dolomedes that inhabit North America, north of Mexico. This semiaquatic creature can be found on or near water and does not construct webs for itself like other spiders typically do. Its appearance can vary from brown to tan, grayish hues – sometimes with stripes, but often without them.
Those with a bold white or tanned stripe running down either side of the body are pretty noticeable, and it’s no different for striped fishing spiders. An intricate pattern can be seen on their abdomens, with dark W-shaped marks separated by white “Ws” between them. Atop the carapace (head) lies a clean line that runs all along its center – making these creatures awe-inspiring to behold!
Striped fishing spiders: Habitat.
The striped fishing spider in Colorado is commonly found near any water body, especially in fast-flowing streams. It typically rests on the stream’s edge with its feet spread across the surface. Its specially adapted hairy legs allow it to move swiftly over land and water – so much so that it can quickly traverse a creek bank or sprint among rocks at a gravel bar.
Striped fishing spiders in Colorado are savvy predators, controlling many small aquatic animals and insects. Unfortunately for them, they are also easy prey to larger creatures such as fish, frogs, dragonfly nymphs, and birds – particularly their young ones. Thus these spiders must be ever-vigilant to survive!
Common house spider in Colorado: Description.
The common house spider in Colorado comes in many muted shades, such as gray, tan, brown, or yellow. It also has darker skin patches or stripes running through its primary body color. The abdomen of the common house spider is higher than it is long and round in shape. Most common house spiders have darker-colored legs with bands or rings of color on them.
In the United States, females have yellow legs, and males have orange legs.
The larger female common house spider in Colorado ranges from 0.12 to 0.18 inches. Due to their poor vision, these spiders usually do not flee from or even notice the approach of humans. Such poor vision is common among all web-weaving spiders.
There are over 200 species of common house spiders in the United States. The messy, billowy webs they construct easily identify them. These cobwebs function perfectly as entanglements for prey.
Common house spiders in Colorado are part of the family Theridiidae (the widow family) and use their combed rear feet to pull silk from their spinnerets and toss it over entangled prey to immobilize them further.
Common house spider: Habitat.
One of the more interesting habits of the common house spider is the number of old, abandoned webs it leaves behind. The common web spider appears to select locations to create a web randomly, and then if they turn out to be unprofitable, quickly relocate their web to another site.
Inside your home, common house spiders build webs in the upper corners of bedrooms and living rooms, closets, sheds, garages, basements, crawl spaces, and even under your bed or behind your toilet.
Since most of the insects a common house spider preys on are drawn to natural light, they will build webs near windows.
Outside your home, common house spiders will create webs under eaves and within natural areas such as the entrance to a cave, hollowed logs, and barns and stables.
What do Common house spiders eat?
After the prey is entangled in its web, the common house spider will throw other silk over it and bind it securely and helplessly in a tight shroud of webbing. The spiders will then bite the immobilized victim and inject it with venom. The venom liquefies the prey’s internal organs and makes it easier for the common house spider to digest its meal.
The common house spider captures and eats flies, wasps, bees, cockroaches, mosquitoes, and other household nuisances in its web. Drained husks of prey get snipped from the web and fall to the ground below.
Cellar spiders in Colorado: Identification.
Cellar spiders in Colorado range from less than a 1/10th of an inch to 2/5ths in length. They have peanut-shaped bodies and oversized leg lengths, with some cellar spiders having long spans of nearly two inches.
The length of their legs is one key identifier; most cellar spiders have legs four times as big as their bodies. The other identifier is the body width being three times as wide as long.
They have eight eyes (grouped as two laterals of three and two smaller eyes whose borders touch each other. Cellar spiders have bodies that are colored gray, pale yellow, and brown and sometimes even appear as clear —with chevron marking.
Cellar spiders are found in every country and continent except Antarctica.
Related: How to identify the Brazilian wandering spider.
Cellar spider webs.
Cellar spiders make unsophisticated and unusual webs for a spider.
Like black widow spiders, they wait for their prey while hanging upside down. When prey is detected, cellar spiders vibrate their webs with their bodies, and this helps further entangle any insects caught in it.
When cellar spider bite, they inject a toxic venom (though it cannot harm a human) that is legendarily thought to be the most potent venom in the spider kingdom. This legend has yet to be scientifically proven.
Cellar spiders do not repair, clean, or remake their webs. Instead, they build additional layers on existing webs. This habit may save them time and energy, but in your home or barn, it quickly makes the web of a cellar spider conspicuous.
Long-Legged Sac Spiders in Colorado: Description
The Long-legged Sac Spider (Cheiracanthium mildei) hails from Cheiracanthiidae and is more famously known as the Northern Yellow Sac spider – a title it shares with many other spiders in its genus.
Characterized by its paler green or tan hue, the Long-legged Sac spider in Colorado has darker brown palpi and chelicerae, making it easily distinguishable from other spider species.
Generally measuring between 0.3-0.4 inches in length, the long-legged sac spider is equipped with double claws at the end of each leg, the front pair being notably more extended than the rest (up to two times as long).
The eyes of this spider contain a tapetum lucidum, which acts like a mirror to reflect light once illuminated. Unfortunately, the shape of the tapetum can’t form clear images; yet it may be beneficial for navigating by detecting polarized light from above. Thankfully, although these spiders can bite humans, their effects appear mild.
Banded garden spider in Colorado: Identification.
The banded garden spider in Colorado (Agriope trifasciata) female may reach up to 1.0 inches in length, making them slightly smaller than the yellow garden spider. Its carapace is adorned with silvery hair. Its elongated oval abdomen tapers off at the posterior into a point without humps or notches like the yellow garden spider.
The background color on its abdomen is usually pale yellow/silver, along with multiple black lateral stripes for contrast. At the same time, their legs are also marked by lighter spots or bands among a paler hue of yellow.
Males of this species rarely exceed .2 inches in length, their abdomens a striking white. Immature banded garden spiders boast an almost entirely white dorsal surface to the abdomen. Furthermore, these arachnids’ egg sacs possess a similar texture and color as that of the yellow garden spider.
Further recommended reading about spiders.
Spider pages: Learn how to identify and avoid these spiders.
Can house spiders hurt you? Are house spiders Venomous?
Do Spiders Sleep? Do They Dream like Humans?
Black Spiders: How to identify them.
Long-Palped ant-mimic sac spider.
The most venomous spiders in the world.
Red house spider identification.
Orb weaver Spiders: How to identify and get rid of them.
Common house spiders: How to Identify and get rid of them.
Six-Eyed Sand Spider: Is the White Sand Spider Dangerous?
10 biggest spiders in the world.
Giant Huntsman Spider: How to Identify the Largest Spider
Brazilian salmon pink bird-eating tarantula
Brazilian Giant Tawny Red Tarantula
Colombian Giant Redleg Tarantula
Cerbalus Aravaensis: Middle East’s Largest Spider
Camel spiders: Myths and Facts.
Net-casting spiders: How to identify these spiders.
White-tailed spider: How to identify and manage.
Katipo Spider: How to identify New Zealand’s venomous spider
Brown widow spider: How to identify and avoid the false widow.
Redback spiders how to identify them and prevent bites
Funnel weaver spiders vs funnel-web
Cellar spiders how to identify and get rid of them
How to identify the wolf spider
How to identify the hobo spider
Brazilian wandering spider how to identify and avoid
Huntsman spider how to identify the eight legged freak
Jumping spiders how to identify these harmless hunters
Black widow spiders how to identify and avoid
Tarantulas appearance diet and mating