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How to Identify Spiders by Their Characteristics

It may seem a simple task to identify spiders by their markings and characteristics. But, it's easier said than done. Most spider species are so similar that only trained arachnologists and some entomologists can identify them through a microscope and years of specialized training. For most purposes, though, you can identify common species, or at least the genus, by learning their physical characteristics, habits, natural ranges and habitats.

Things You'll Need

Cup
Thick piece of paper (card or similar stock)
Clear, lidded container
4- to 6-inch piece of measuring tape
Plastic tweezers

Instructions

- 1
  Place the cup over the spider to capture it.
- 2
  
  The cup serves as an inescapable temporary holding place for the spider.
  
  Slide the thick piece of paper underneath the cup to pick up the spider.
- 3
  
  Any type of measuring tape section will work.
  
  Place the measuring tape on the floor of the clear, lidded container. You can also tape 4-inch sections of measuring tape against the length and width of the floor of the container and one 4-inch section vertically on a wall of the container. The measuring tape will help you determine the spider's body length and leg span; the vertical piece can help you determine the length and leg span if the spider climbs the sides of the container.
- 4
  Shake the spider gently into the container and firmly close the lid.
- 5
  
  The black and yellow argiope is a large, conspicuous spider.
  
  Study and observe the spider and take notes. Characteristics to look for are length of the spider, spines or hairs on its body or legs, colors, markings such as stripes or spots and number and arrangement of eyes. While most spiders have eight eyes, some have only six or other numbers. The brown recluse, for example, has six eyes in a "U" shape, which helps identify it from other similar-looking species. Some spiders also have distinctive markings. Examples include the red to reddish-orange hourglass on the abdomen of the widow spiders; the fiddle on the cephalothorax -- combined head and thorax -- of the brown recluse and other Loxosceles spiders; or the black abdomen with yellow, yellowish-white or orangish streaks and spots of the black and yellow argiope.
- 6
  
  Close-up views can yield more characteristics than at a simple glance.
  
  Pick up the spider gently with the plastic tweezers. Hold the spider under a magnifying glass to get a better look at the eyes or other characteristics. This is optional, however, because some people don't like to get that close to spiders even though most are completely harmless.
- 7
  Borrow a field guide on spiders from your library. Field guides often have detailed photographs and descriptions of common species. Try to get a guide that is particular to your region or state; native range is a key point in trying to identify a spider. Some spiders look similar to species that live in other parts of the country or on the other side of the world.
- 8
  Search online at university and educational websites. Type "site:.edu" at the beginning of your search phrase in a search engine. For example, if you are in Kentucky and have a black and yellow spider, type "site:.edu black and yellow spiders in Kentucky." Many educational websites have photographs and detailed descriptions of spiders.
- 9
  Take the specimen to your university-affiliated cooperative extension service, or call a local university and ask to bring the specimen into the entomology department. If the university or cooperative extension has an arachnologist, you're even in more luck.

Nature