Which spiders are living in my home?

By Dr. Killigan
Which spiders are living in my home?

I find a spider’s web more wondrous in construction than the tapestries bedecked on castle walls, the adornment of metal and stone dangling round a queen’s neck, and the brush strokes on the canvas of Willem de Kooning. Have you ever seen anything so delicate and precise…and stopped to wonder at its complexities, and the beauty and the awe of the world—big and small—that unabashedly surround us? I have long been fascinated by these eight-legged creatures.

What are spiders?

Spiders have multiple eyes (in pairs) and, because they have eight legs (not six) and lack antenna, they are technically not insects.

  • Spiders (Araneae) breathe with their lungs and their tracheae. They are the only animal group that breathes simultaneously with their lungs and their tracheae. (Tracheae are small tubes that allow the passage of air and open directly to the surface through small holes called spiracles.)
  • Some spiders are natural recyclers. The orb spider recycles the amino acids that make up the silk proteins of its web by simultaneously ingesting the silk and dismantling their damaged web every day. An American species of spider uses the webbing to wrap its egg sac.
  • Not all spiders build webs and the built-webs are highly diverse. Around 50% of spiders build webs to catch their prey. These range from the fragile and much admired orb web and the less welcoming long-leg spider tangle web to the extensive, long-lasting, multiple-occupants-over-time funnel webs of large house spiders. 
  • A spider’s silk is multi-purpose. It can be used (1) to build webs, (2) to hold egg sacs, (3) to wrap up prey, (4) as a safely line when escaping predators, (5) to hold an underwater air supply—for water spiders—and (6) to disperse spiderlings to wherever their new homes will be.

Remember the spiderlings, to Wilber’s disappointment, being carried away in Charlotte’s Web? He had patiently waited for them to be born and then cried out in sorrow and panicked when, on a warm summer day, they raised their abdomens, let out strands of silk, and rose on the air currents to be lifted and carried away. They used their silk to disperse themselves.

How many spiders are in my home (and on earth)?

While I would love to note the average number of spiders in a person’s home, the figures are so varied that there is no average to be had. Though, I can tell you that there are about 3 million spiders for every person on the planet. I can also overwhelm your senses by writing that, if spiders could eat human flesh, it could take less than a year for spiders to devour the entire human race. According to a study by Martin Nyffeler and Klaus Birkhofer, spiders consume about 400-800 million tons of biomass annually, which could easily encompass you and I (and all of our family, friends, and neighbors) in a 12-month period.

What are common house spiders? 

Common house spiders are usually seen in the autumn months when males leave their webs in search of females. The term "common house spider" is used to describe numerous different types of spider species worldwide and those (commonly) found in and around human dwellings. Here, I will be discussing only the eight that are most common in North America.

These eight common North American spiders range in size from the relatively tiny domestic house spider (Tegenaria domesticato) to the larger giant house spider (Eratigena atrica), the latter of which can reach a length—with its leg span—of 4.7 inches.

  • Yellow sac spider, Chiracanthium inclusum. It is small, measuring at ¼ of an inch in length, and is the most commonly encountered spider in gardens. It is found worldwide.
  • Brown house spider or false widow, Steatoda grossa. Measuring at  ¼ to ⅜ of an inch, it is also small, and has a cosmopolitan distribution. It is prevalent in the southern and western states.
  • America house spider, Parasteatoda tepidariorum. It is a cobweb spider and the most common spider found throughout North America. 
  • Cellar spider, also known as daddy long-legs, Pholcus phalangioides. It varies in color, but is often pale yellow, light brown, or grey. It is seen in large numbers in the fall and creates scuffy webs in room and cupboard corners. 
  • Domestic house spider or barn funnel weaver, Tegenaria domestica. It is most notably found in sheds and barns, around and in the crevices of doors, as well as in the cracks of rock faces and under rocks and boards.
  • Giant house spider, Eratigena atrica. It is a very common spider in Washington and Oregon, though independent populations have also been recorded around the Great Lakes in Wisconsin and Michigan. 
  • Hobo spider, Eratigena agrestis. It is sometimes called the aggressive house spider, though not actually aggressive. (This misconception is often used to help fuel fears about the potential hazards of this spider.) It is most prevelant in the Pacific Northwestern parts of the United States and British Columbia.
  • Southern house spider, Kukulcania hibernalis. It is predominate in the southern states of the United States.

How do I identify which of these spiders I have in my home?

Identifying the common spider species in your home can tricky, but not impossible. To do so, look at the size of the legs in proportion to the body. Some spiders have long, thin legs (like the yellow sac), while others have large, thick hairy legs (like the domestic house spider). Some spiders (such as the southern house spider) have fine, velvety light gray hair on their abdomens, while others have spiny hair coming off of their legs (such as the hobo spider).

In identifying the type of spider, you’ll want to ensure that you do not have a brown recluse, black widow, or a hobo spider in your home, as these are the three most venemous spiders in North America. The have fangs and venom that can penetrate (aka bite) human skin.

  • Brown recluse spiders, Loxosceles reclusa. They have tell-tale violin shapes on their backs, a medium brown body and brown legs, and six eyes. They prefer warm, dry places, like a shed or woodpile.
brown recluse spider (Loxosceles reclusa)

Image: Brown Recluse Spider

  • Black widow spiders, Latrodectus. They are a striking shiny black color with a bright red hourglass shape on their abdomens. They have long legs that taper into points, and typically dwell in woodpiles and under leaves.
Black widow on web (Latrodectus)

Image: Black Widow Spider

  • Hobo spiders, Eratigena agrestis. They are brown with chevron-shaped yellow markings. They make their webs in cracks, corners, and holes, and can commonly be found in woodpiles and other sheltered locations.
Hobo spider on ground (Eratigena agrestis)

Image: Hobo Spider

How long do spiders live?

A spider’s life span varies greatly, depending on the species of spider and whether we’re talking about a female or male, as female spiders tend to live longer than male spiders. This could be because of genetic strength, as female spiders are responsible for laying eggs and taking care of their young. It could also be because some species of female spiders actually kill or consume their mate after they have finished mating. (In some cases, the female will even catch the male when he attempts to escape.) Many male spiders reach maturity within two years and die after mating.

Here are some spider life span examples: 

  • The common house spider (Achaearanea tepidariorum) lives for about 1 year. 
  • The common barn funnel weaver (Tegenaria domestica) has a life expectancy of up to 7 years. 
  • Black widow spiders (Latrodectus) can live for up to 3 years. 
  • Tarantulas (Theraphosidae) can live anywhere from 10-30 years.
  • Male wolf spiders (Lycosidae) often live no more than one year; however, their female counterparts are able to live several years. 
  • The average trapdoor spider (Ctenizidae) lives 5-20 years, though the world’s oldest spider was a trapdoor spider—and lived to be 43. 

Is it good to have some spiders in my house?

A house-dwelling spider provides free year-round pest control, taking care of other pests such as mosquitoes, flies, fleas and even cockroaches. I’m not suggesting that you allow them to freely take up residence in your home, but I am saying that there is wisdom in allowing the occasional spider—neither dangerous or aggressive—to live in your basement or attic, (where you or any house guests are least likely to have 1:1s with them).

Pocket fact: The huntsman spider (which is different from the giant huntsman spider), American house spider, and jumping spider have all been known to eat cockroaches. Though they may not be able to take on a whole adult cockroach, they will do enough damage to end the life of these detested pests.

Spiders oversee their own population control, as they will kill their own. When spiders come into contact with one another, it is a fight to the death. They will even take on their mother or one of their siblings, born out of the same egg sac. The larger spider usually wins. Hence, one day you may notice a larger population of spiders in your basement and the next dark-sole-lightbulb experience you have finds but just a few, a few that have been greedily feasting and suddenly appear quite fat. 

If you look at the benefits of spiders, you may find yourself wanting to keep a few of these 8-legged arachnids around. 

  • They feed on common indoor pests. In fact, one spider can eat 2,000 insects in one year. 
  • They help curtail disease. These diseases can be transmitted to humans and our beloved pets
  • They get rid of one another. The most common long-legged cellar spiders (daddy long leg) are known to kill black widow spiders. 

How to get rid of spiders in the home

Arachnophobia is an intense fear of spiders, placing second in terms of people’s fears. (First is public speaking). Some folks are not only scared of spiders, but consider the spider itself as scary. A spider’s presence can elicit a "disgust response" and cause people to flee their homes rather than deal with this miscreant.  

Bulb duster for non-toxic insect powders

We all try to avoid experiences that make us feel uncomfortable. If spiders make you feel uncomfortable, I suggest the use of our Insect Buster. Filled with diatomaceous earth or Dust to Dust, this super-quality, single-purpose, must-have tool that is designed to last a lifetime will help eradicate many pests, including ants, wasps, and spiders.

Diatomaceous earth (DE) is made up of the fossilized remains of tiny aquatic organisms called diatoms. These diatoms have very sharp, knife-like surfaces that scrape a spider’s razor-thin exoskeleton and stick to it like burrs as it walks through the powder. This scratching, scraping, and sticking cuts through the spider’s cuticle, removing oils and fats from its exoskeleton (its defense and protection), thus causing the spider to dry out and die from dehydration.

A second benefit of diatomaceous earth is that, as long as it remains dry and undisturbed, it is effective.

Dust to Dust Non-Toxic Insect Powder is a safer and more effective alternative to diatomaceous earth for insect control. Dust to Dust is proven to have kill times up to 50% faster than diatomaceous earth.

Protect you home from these primarily poisonous arachnids. Use the Insect Buster and disperse non-toxic insect powder where spider activity abounds, whether this be in corners of your basement, your attic, or around windowsills in your kitchen. Disperse DE or Dust to Dust in common entry points too, such as gaps around doors and windows. Spiders must come in contact with these powders in order for them to be effective.

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  • We get quite a few wolf spiders and harvestman up in my neck of the woods. They look intense, but are quite harmless!

    Mitch C on
  • Great info! I’m surprised by the longer life span of some of these spiders. Imagine a resident tarantula that lives in your home for longer than your kids!

    Jason on

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