Good Spiders vs Bad Spiders: Which Spiders Should You Leave in Your House?

Written by Kyle Glatz
Published: October 17, 2022
© Kaldari / Creative Commons – License / Original
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Spiders get a bit of a bad reputation, but much of that is unearned. Over 40,000 species of spiders exist and they number in the quadrillions. Yet, spiders rarely kill human beings. Still, they look scary and it’s easy to confuse a harmless woodlouse spider for a brown recluse. That’s why this article is going to focus on differentiating between good spiders vs. bad spiders.

We’ll take some time to show you what makes a spider good and what makes them bad. That way, you’ll know which spiders you will want to eliminate in your home and which ones you’ll want to leave to their own devices.  

The Key Differences Between Good Spiders vs. Bad Spiders

Good spiders are different from bad spiders in venom and size.
Good SpidersBad Spiders
Venom– Has mild venom that is used to disable or kill their prey
– Venom cannot cause significant or lasting harm to humans, like cellar spiders
– No or few reports of human allergic reactions to bite
– Have deadly neurotoxic venom that can cause death in humans, like the black widow
– Deliver a bite that causes necrosis in the area surrounding a bite, like a brown recluse
– Commonly causes allergic reactions in humans, like wolf spiders or huntsman spiders
Size– Small spiders are scarcely noticeable and not likely to cause alarm
– Have a body size of less than an inch
– Possess large bodies that cause fright and adverse reactions that can lead to injuries or anxiety
– Have large bodies that measure 1-2 inches
– Possess total legspans that measure 2 inches and higher
Prey– Consumes other harmful creatures, like deadly spiders, mosquitos, wasps, lanternflies, roaches, and more– Consume helpful creatures like honeybees
– Most of the time, bad spiders and good spiders have similar diets
Risk of Biting– Only bites as a last resort or when pressed against human flesh– Bites when handled
– Lives in places where humans frequent putting them at a higher risk of getting bitten
– Ground spiders are more likely to run afoul of a human than web-builders

The 4 Main Differences Between Good Spiders and Bad Spiders

The key differences between good spiders and bad spiders come down to the potency of their venom and the potential for human allergic reactions. Some spiders have venom that can seriously injure or kill a human being, like a black widow. Other spiders have weak venom that doesn’t do much lasting harm, like a grass spider.

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Also, good spiders are those that have positive traits and have a low chance of causing a serious allergic reaction. Minus their size, wolf spiders could be considered good spiders if it wasn’t for their propensity to cause serious allergic reactions in humans that require hospitalization. Since they have a high chance of causing allergic reactions, especially relative to a good spider like the grass spider, wolf spiders are probably not something you’ll want to leave crawling in your home.

These are just a few of the ways to determine good spiders vs. bad spiders. We’re going to provide four total key differences between good and bad spiders so you know which kinds to keep from your home and family.

Good Spiders vs Bad Spiders: Venom

Black Widow - Dangerous Spider
Bad spiders have venom can cause serious injury.


Good spiders have venom that is relatively incapable of hurting people, but bad spiders have venom that can seriously injure or kill a person. Most, if not all, spiders have some kind of venom. However, not all venom can hurt people due to a human’s size, a lack of potency, or an inability to deliver the venom into a human’s body.

Thus, good spiders would be grass spiders, cellar spiders, jumping spiders, and others with relatively mild venom. Black widows, brown recluses, and yellow sac spiders can cause serious injuries to people, so they are bad spiders. Furthermore, spiders with venom that causes more allergic reactions than most others, like wolf spiders or huntsman spiders, can also be considered bad spiders.

If you see a black widow, brown recluse, yellow sac spider, or brown widow spider, it’s imperative to kill them or get them removed from your home.

Good Spiders vs Bad Spiders: Size

A good spider is scarcely noticeable, but bad spiders, at least ones you don’t want in your home, are excessively large spiders. Generally, good spiders have a body size of less than an inch and a legspan that is small. Their size isn’t necessarily what makes them good, but most people don’t want a massive spider lurking around their homes. Smaller ones get a pass if they do something beneficial for the household.

Bad spiders are the large ones that scare people and frighten them into falling or experiencing anxiety. Spiders with a body over an inch long and legspans that are even bigger, from 2 inches and up, are probably not the house guests you want. Although it’s not truly fair to say they are bad based on size alone, large spiders are not the ones people want to live with.

Good Spiders vs Bad Spiders: Prey

daddy long legs
Cellar spiders eat more dangerous spiders, like black widows.


Good spiders eat pests and creatures that can harm humans. For example, cellar spiders are known for feasting on black widows, giving rise to the falsehood that they’re more dangerous than them. In that sense, cellar spiders are good spiders. Spiders that eat mosquitos, wasps, and lanternflies are also good.

Bad spiders are those who feast on beneficial insects or creatures. For the most part, spiders aren’t that picky, so the overlap between good and bad is subjective. If you have a pest problem that spiders are keeping at bay, like wasps, then they’re good spiders.

Thus, prey and diet can be used to help build the case for a good spider, but it shouldn’t be the only criterion.

Good Spiders vs Bad Spiders: Risk of Biting

Bad spiders are those that bite with less provocation than others. Then again, if you harass most spiders and press them on your skin, they’ll probably bite you. However, bad spiders could be considered those that hide in places that humans frequent or that give little warning against a bite.

Most people see spider webs before touching them, giving them some time and space to avoid a conflict with a spider. Ground spiders that don’t spin webs to catch prey, like wolf spiders, may hide in a place where a human could reach, like between boxes in the basement.

So, bad spiders are those that hide in places where they are most likely to interact with humans. Sometimes they’re web-builders, but other times they’re not

The Spiders You Don’t Want in Your House

Now that we’ve identified the features of good spiders and bad spiders, we want to talk about the spiders you don’t want in your home. You shouldn’t mind seeing grass spiders, cellar spiders, or jumping spiders if you don’t mind the presence of arachnids.

Still, you don’t want any of the undeniably bad spiders in your home, like:

These are some of the most common spiders that can pose a threat to you or your loved ones, including pets. However, many other types of spiders exist that can cause you problems. It’s best if you take some time to learn about what spiders live in your area so you’re prepared to confront potentially harmful arachnids.

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About the Author

I've been a freelance writer since 2013, and I've written in a variety of niches such as managed service providers, animals, and retail distribution. I graduated from Rowan University in 2014. When I'm not working, I enjoy playing video games, reading, and writing for fun.

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  1. National Library of Medicine, Available here:
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  3. National Library of Medicine (1970)