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is spider poisonous

How to Tell if a Spider is Poisonous: The Only Guide You Need



Are you trying to learn how to tell if a spider is poisonous? If yes, you should check out some of our best tips and tricks here.


It’s almost surprising that a new movie based on Arachnophobia hasn’t been made recently. With new CGI and effects, you could see a lot of close-up vanity shots of everyone’s least favorite crawling things.

You don’t have to be afraid of spiders or excited for tired movie remakes to want to know how to spot the dangerous ones. Film visuals do make a great touchstone when you want to know how to tell if a spider is poisonous.

Overall it’s not too hard to determine the dangerous spiders from the safe ones. In North America, there are roughly 3,400 species of spider and only three varieties pose a human risk. Still, the damage that can be done by those three is no joke.

The number of species that can create irritation and problems for pets gets broader. Let’s get up-close and learn what to look for.

How To Tell if a Spider Is Poisonous

If you’re wondering, “Should I kill spiders in my house?” the answer is generally a no.

The vast majority of spiders are both not harmful to humans and pets but actually helpful. Spiders eat a lot of other pests and keep things tidy. A few musty cobwebs here and there is a small price to pay for keeping other infestations at bay.

But, let’s face it, spiders are creepy. They have entirely too many legs and it isn’t exactly a pleasant sensation to feel one skittering across your arm or leg.

On top of that, people hear horror stories of the damage a venomous bite can do. The brown recluse has been especially dangerous since it first got serious study started in 1964.

It’s prudent, then, to be aware of how to spot a dangerous spider either by spotting the critter itself or the tale-tale signs of its habitat.

Venomous vs Poisonous

A quick note, the three spider varieties covered here are venomous. These are animals that bite and inject a type of venom that causes harm.

You may have heard that a common house spider sometimes referred to as a Daddy Long Legs is venomous but lacks fangs. That’s absurd, but there are spiders that are poisonous, meaning they can harm you if they are eaten. Outside of a trend for side-shows in the late 90s, most people aren’t eating spiders.

Pets, on the other hand, don’t always know what to avoid. So we’ll point out a few to look for to keep your barkers and meowers safe as well. It’s especially important to keep pests out of businesses where injuries can harm customers.

Coloration and Markings

Nature has a weird way of announcing its intentions. Prey creatures that are poisonous or dangerous to others tend to be brightly colored to warn predators away. At the same time, predatory animals tend to be dark and stealthy so as better to sneak up on prey.

Venomous spiders end up with a few markings and colors that make them distinct but their small size and speed make identification difficult.

Hobo Spider

The hobo spider is a less talked about venomous spider. It has the fewest distinct markings and looks the most like other house spiders. They also tend to be defensive biters unlike the other two.

These are brown throughout in overall color. Along their abdomen, they have a yellow marking resembling a dull striped pattern like it ate a yellow wasp. The legs tend to be lighter in color and missing the darker bands of more common spiders.

Their head is bulky with a fuzzy appearance not dissimilar to the Wolf Spider.

Black Widow

The easiest venomous spider to identify is the black widow. There’ve been plenty of television shows and tropes to help cement its black hues and bright red hourglass in our minds.

While all black widows do have shiny black coloring, they don’t all have the distinct hourglass. The hourglass may be more orange than red. You’ll also find the hourglass missing or incomplete leaving a series of red or orange stripes and dots.

The female is more distinct and easier to see, they are also more venomous. The males tend to be smaller and are known to be missing the markings altogether.

Brown Recluse

Though black widows have the distinction and reputation, the brown recluse has the nastier chemical cocktail on tap. They also tend to hide and don’t show off their sinister intentions in such an obvious way.

Brown recluse spiders are brown overall but more of a tan. They blend easily with wood and lighter soils.

A few subspecies, often referred to as fiddlebacks, have a darker marking on the head. This resembles a tiny violin and crosses the head and thorax.

Making this pest even harder to identify is that they can range from a medium brown to an almost white and even the species known to have the violin shape don’t always have it.

The most distinct feature of the brown recluse is actually the eyes. They only have six instead of eight. these are found in pairs running up the head. Getting close enough to count the eyes is not recommended.


Thankfully, not all spiders are found in all areas. Depending on where you live, you can avoid worrying about some species.

That said, due to the climate shifting, some animals and insects are migrating to new habitats. Also, many building materials and foods are sourced from around the world. This leads to new species taking root in previously uninhabited locations.

It’s important to keep in mind the areas that are most likely to house a particular venomous spider variety. In addition, you want to look out for the signs of their nests and webs in areas they are more likely to hole-up.

When you find nests, turn to a professional to remove them quickly.

Hobo Spider

Hobo spiders spend their time in small cracks and crevices. As their name suggests, they tend to be solo and out of the way. They don’t have a preference between stone or wood and are found equally in both.

They don’t tend to attack unless provoked and it takes a major intrusion into their territory to get that reaction. Before moving bricks or woodpiles, give a scope with a light for webs and small holes.

They are found most commonly in the Northwest between Oregon and Canada.

Black Widow

Black widows prefer to make their webs nearer the ground and in dark areas out of sight. They prefer a warmer place that also has access to a food supply. A tidy, cold area is their kryptonite.

They are known for making ‘drunken webs’ which break from an orderly circular shape and have odd angels and gaps. The webbing is stronger than most spiders so a thick web with odd gaps is the biggest tell if you don’t see the spider itself.

Black widows can be found everywhere in North America.

Brown Recluse

The brown recluse enjoys warmer temperatures and a lower altitude. They are rarely found beyond Colorado and don’t travel farther north than Nebraska.

That said, there is a species of fiddlebacks that is unique to Hawaii. This is the only species found west of the Rockies.

They also look for warm and dark locations to spin their webs and nab their food.

Their webs also have irregular sizes and gabs but look fluffy and layered. Within a recluse web, you find a habitat shelter. This is a larger patch on the web that looks almost like a picnic area.

How To Treat a Bite

Treating bites has come a long way since the 60s. Current technology has taken strides to understand the chemical makeup of the venoms and how they operate.

In the event of a bite on you, a family member, or a pet you want to take action quickly. The area of a bite will be swollen and tender. The most common symptoms are nausea, headaches, and dizziness. Less common symptoms include a rash, sweating, and spikes in blood pressure.

Brown recluse bites can lead to necrosis, which can eat away at the skin and tissue around the bite.

Treat a bite by applying ice to the area. Follow up with antihistamines and antibiotic ointment to keep the area from itching. Itching a bite can break open cells and release more venom.

If you spot one of the three varieties of venomous spiders listed here, seek immediate medical attention. Hospitals are equipped to identify the venom by type and offer antitoxins as well as treat the symptoms of the venom in your system.

Removal and Protection

When you do your diligence in learning how to tell if a spider is poisonous or venomous, you have taken an important step. From there, it’s time to get help in removing the pests and keeping them from coming back.

Contact us about our residential pest services to learn more about the steps we take and the processes we use. The idea is not to simply remove dangerous spiders from your home but to keep them away long-term.


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