Spider Identification

- Know which species are venomous -

Summary: Spider identification can be tricky and except for a few common species can not be done based on color patterns alone. Fortunately very few species pose any real threat in terms of a venomous or poisonous bite. Learn which, if any, venomous species occur where you live then learn how to avoid them.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

The spiders are an extremely large and diverse group with thousands of species. While most spiders are harmless a few are dangerously venomous. Spider identification can be very tricky once you get below the level of family classification. Species and genus-level determinations generally require a good stereo-microscope plus some experience. You may, however, be able to figure out higher level classification by comparing your specimen to a drawing or photograph.

What's important for most people is to be able to accurately identify the poisonous or venomous species that occur around where they live. In the US three species are commonly blamed for venomous bites: the hobo spider, the brown recluse spider and the black widow spider (see links above and  Common Venomous Spiders In The US).

Once you learn to recognize and avoid the few venomous species where you live you can relax. For all other spiders you should use a field guide with good color pictures and range maps to do your identification. Recently some good online resources have become available as well. One such is SpiderID, an online community devoted to spider identification.

color pattern is NOT reliable for spider identification

Color patterns alone are not reliable enough for accurate spider identification. This scary-looking spider is actually harmless.

Spider identification guide

Most experts agree that you'll need a microscope or hand lens and good reference materials to identify even common spiders. You should not rely on color patterns alone because these can be very confusing and not consistent from specimen to specimen.

A better approach is to identify particular characters in each species that distinguish it from other, similar species and a guidebook is the only way to do this accurately. There are many books and online resources available but How to Know the Spiders (Pictured Key Nature Series), available through used booksellers, is an in-depth and specific guide to spider identification that will be useful for non-experts.

Control indoor spiders with sticky traps

The most dangerous indoor spider species can be effectively trapped with homemade or commercial spider traps. See our recommended supplies and How To Use Sticky Traps For Indoor Spiders for information about constructing sticky board traps for household spiders.

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