Identify Spiders

There are over 44,000 spider species in the world, and the only way to conclusively identify one is to have an expert examine its anatomy under a microscope. However, familiarizing yourself with spiders’ defining characteristics can make your guesses about the spiders you encounter more educated. If you can stand to look at that giant, hairy spider in your bathroom (or that tiny one in your basement), check its physical features and habits for clues to its identity. Most of the time, you’ll end up relieved to find that it’s not dangerous.

Steps

Recognizing Venomous Spiders

  1. Determine if you've got a brown recluse on your hands. When it comes to spider identification, the first one you'll want to rule out (if you live in North America) is the brown recluse. This is the most dangerous spider in the US, and is found most often in the Southeast and Midwest.[1] A brown recluse bite can cause infection, and medical attention is usually necessary. Here's how to know if the spider is a recluse:
    • Look for the tell-tale violin shape on its back. The brown recluse has a medium brown body and legs, with a slightly darker brown violin shape on the back.
    • Count the eyes; if there are six, it might be a recluse. The recluse's eyes are arranged in pairs, with one pair in front and a pair on either side.[2]
    • Analyze where you found the spider; if it's in a warm, dry place, like a shed or woodpile, it might be a recluse.
    • The brown recluse is known to be aggressive, rather than hanging back when it encounters someone.
  2. See if Identify a Black Widow. Black widows are common in the Southern and Western states in the US. When they bite, they release a neurotoxin that causes pain and other severe effects, especially in children and the elderly.[3] Here's what to look for:
    • These aptly-named spiders are a striking shiny black color, with a bright red hourglass shape on the abdomen.
    • Black widows commonly dwell in woodpiles and under eaves.
    • They have long legs that taper into points.
  3. Find out if it's a hobo spider. This is the third major venomous spider in the US. It's commonly seen in the Pacific Northwest. It is not quite as dangerous as a brown recluse or black widow, but medical attention is still necessary when a bite occurs.
    • Hobo spiders are brown with chevron-shaped yellow markings.[3]
    • They make their webs in cracks, corners and holes, and can be found in woodpiles and other sheltered places.
  4. Rest assured that most spiders aren't dangerous. All spiders have a small amount of venom, but many spiders that look decidedly creepy won't actually cause a dangerous reaction when they bite. If you’re in North America and the spider you see can't clearly be identified as a brown recluse, black widow, or hobo spider, it probably won't cause you any harm.
    • In fact, having some spiders around is beneficial to the environment; they keep insect populations down so you don't have to use pesticides.
    • If you live outside of North America, consult one of several widely available guides to learn about the dangerous spiders in your locale.[4]

Evaluating Its Appearance and Behavior

  1. Notice the spider's coloring. Take note of the spider's primary color - usually a shade of brown (like the Identify-a-Mouse-Spider), black (like the Identify-a-Cobweb-Spider), or grey. Also look for color variations (as with the Identify-a-Jumping-Spider), subtle or not so subtle, that will give you a clue as to what type of spider you're looking at.
    • Does the spider have spots, or coloration in a striking shape like the Identify-a-Brown-Widow-Spider hourglass marking or the brown recluse's classic violin?
    • Are the legs the same color as the body?
    • Note that many species of spider have similar coloring, so looking at this characteristic alone won't be enough to give you a definitive answer.
  2. Look at the shape of the legs. If possible, examine the spider’s eight legs a bit more closely. Look at the size of the legs in proportion to the body. Some spiders have long, thin legs (like the Identify-a-Yellow-Sac-Spider), while others have stocky, thick legs (like the Identify-a-Wolf-Spider). Some spiders (such as the Identify-a-Lynx-Spider) have tiny hairs on their legs, while others have spikes (such as the Identify-a-Funnel-Spider) or fur.
  3. Examine the eyes. The number and location of eyes varies widely among different spider species.[5] If you can, get close enough to look at the spider's eye size, count and arrangement. It’s often easiest to take a picture of the spider, then zoom in to see the eye count and pattern.
    • While the Identify-a-Spitting-Spider is one of the exceptions, most spiders have eight eyes, sometimes equal in size (like the Identify-a-Nursery-Web-Spider), but other times with two (like the Identify-a-Portia-Spider) or four of the eight much more prominent; the eyes can also be arranged in many different patterns.
  4. Take a picture of the spider if you can. If you're insistent on figuring out exactly what species of spider you've spotted, take a picture of it. If possible, try to capture a picture of the spider's underside as well as the top. Since so many spiders look alike, it's impossible to know for sure what you're seeing until you compare the spider's image to those of other spiders that have been definitively classified by scientists.
  5. Assess the spider's behavior. Some spiders are aggressive (like the Identify-a-Brazilian-Wandering-Spider), and will start moving toward you when they notice your presence. Others hide (like the Identify-a-Crab-Spider), and still others stay put instead of moving. Pay attention to any other behaviors you notice that could help you figure out what type of spider it is.[5]
  6. Do research to figure out what species it is. If you have a moment after taking note of the spider's appearance and habits, you can use the World Spider Catalog,[4] the online Journal of Arachnology,[6] and other resources put together by experts to look up the spider and compare it to pictures of different species.
    • WikiHow is also a handy source for spider info — check out the identification guides on, for instance: Identify-a-Garden-Spider; Identify-a-Barn-Spider; Identify-a-Redback-Spider; Identify-a-Tarantula-Spider

Considering Other Basic Factors

  1. Make sure it's really a spider. A lot of people think spiders are insects, but they're actually very different. To make sure the creature you've encountered is actually a spider, look for the following qualities:
    • Two body segments. Unlike insects, which have three body segments, spiders only have two.
    • Eight legs. Don't mistake an insect's antennae for legs.
    • No wings. No species of spider has wings. No matter how spider-like the creature may otherwise appear, if it has wings, it's not a spider.
  2. Know what species are common in your region. If you live in New York City, you probably won’t encounter the fearsome banana spider (although it's certainly not impossible). Familiarizing yourself with the species that live in your area is a good way to narrow down the possibilities when it comes to identifying spiders.
    • There are many excellent resources you can use to learn more about spiders. Check out a book from your library or look at spider databases online. You can search according to region.[6]
  3. Look at the spider's habitat. You can learn a lot from the place where you encountered the spider, as well as the web or burrow in which you found it. Answer the following questions regarding the spider’s habitat:
    • Where did you find the spider? Was it in the bathroom, the basement, the shed, outside, etc.? Was it in a dark place (as preferred by the Identify-a-Baboon-Spider), or a place with plenty of light? Was it a wet place (or even in the water, like the Identify-a-Water-Spider) or a dry one?
    • What type of web does the spider have? Is it a classic-looking spider web, a tunnel web (as made by the Identify-a-Purse-Web-Spider), or just a few strands of webbing that aren't neatly woven?

Tips

  • Don’t forget to destroy a Identify-Spider-Egg-Sacs when you are trying to rid your home of spiders.
  • Before going on a vacation, it’s a good idea to familiarize yourself with spiders native to the country or region you plan to visit. Field guides are available at your local bookstore or library.

Warnings

  • Seek medical attention if you are bitten by a poisonous spider, or if you are allergic to spider bites.
  • All types of spiders are important to the eco-system. They are predators that control the pest population in vegetable gardens and fruit orchards. If at all possible, avoid killing spiders; most are not harmful or poisonous to humans.

Related Articles

  • Identify a Black Widow's Habitat

Sources and Citations

  1. ↑ http://www.pestworld.org/news-and-views/pest-articles/articles/identifying-your-spider-infestation/
  2. ↑ http://www.pestworld.org/news-and-views/pest-articles/articles/identifying-your-spider-infestation
  3. ↑ 3.0 3.1 http://www.termite.com/spider-identification.html
  4. ↑ 4.0 4.1 http://research.amnh.org/iz/spiders/catalog/INTRO1.html
  5. ↑ 5.0 5.1 http://www.spiders.us/articles/identification/
  6. ↑ 6.0 6.1 http://www.americanarachnology.org/JOA_online.html

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