What Kind of Bug Is This? Common Bug Groups

Is It a Spider? How to Tell Spiders From Look-Alikes

Spiders: 5 marks to check, what they are often confused with, whether they bite or sting, and where they turn up, quoted from university entomology and IPM sources.

These pages help you narrow a bug down to its group from what you can see. They are not medical advice. Seek medical care promptly for severe symptoms or any sign of an allergic reaction.

Download on the App Store

At a glance

Group: Class Arachnida; spiders are not insects
Body plan: Body divided into two main parts — a cephalothorax and an abdomen; 8 legs; no wings or antennae; the number and arrangement of eyes varies by family (recluse spiders, for example, have 6 eyes arranged in 3 pairs).
Size: Varies greatly by species: brown recluse body not more than 3/8 inch; wolf/jumping spiders about 1/4-1/2 inch; tarantulas about 1-2 inches; hobo-type wandering spiders about 1-1 3/4 inches including legs.
Bites or stings: Most spiders rarely bite people because their jaws are too small; black widow and brown recluse bites are medically significant; about 10% of recluse spider bites cause moderate or greater tissue damage and scarring, while most others only cause inflammation and heal on their own.
Where you find them: Outdoors, commonly found in dark, dry, sheltered, relatively undisturbed places along with their webs; they may also enter homes through cracks and other openings.

How to tell it is one of the spiders

Adult female black widow: shiny black body, slender black legs, and a red or orange hourglass mark on the underside of the abdomen.
The key identifying feature of recluse spiders is 6 equal-sized eyes arranged in 3 pairs (most spiders have 8 eyes).
Jumping spiders build no web; instead they stalk and pounce on prey by jumping.
The jaws (chelicerae) of most spiders are too small to bite through human skin.
Bites or stings from other arthropods, such as ticks, fleas, bees, and wasps, are sometimes mistaken for spider bites.

Often confused with

People most often mix spiders up with:

Ticks

Open the other page and compare its list against the marks above; the differences are usually in the antennae, wings or the way the body is divided.

Bites and stings

Most spiders rarely bite people because their jaws are too small; black widow and brown recluse bites are medically significant; about 10% of recluse spider bites cause moderate or greater tissue damage and scarring, while most others only cause inflammation and heal on their own. Seek medical care promptly for severe symptoms or any allergic reaction.

Pest or beneficial?

Spiders are overall beneficial because they feed on pest insects and other nuisance insects.

Where they turn up

Outdoors, commonly found in dark, dry, sheltered, relatively undisturbed places along with their webs; they may also enter homes through cracks and other openings.

How to photograph it for identification

Get as close as your camera will focus, from directly above, in daylight or a bright lamp. Include the whole body with the legs and antennae in frame; a second shot from the side shows wings and body segments. Put a coin or ruler next to it for scale. For a bite or a bug found on skin or bedding, photograph the bug itself, not the mark. The app names the likely group; use the list above to confirm.

FAQ

Do spiders bite or sting?

What is the quickest way to recognize spiders?

Adult female black widow: shiny black body, slender black legs, and a red or orange hourglass mark on the underside of the abdomen.

Are spiders a pest?

Spiders are overall beneficial because they feed on pest insects and other nuisance insects.

How do I tell spiders from ticks?

Adult female black widow: shiny black body, slender black legs, and a red or orange hourglass mark on the underside of the abdomen. The key identifying feature of recluse spiders is 6 equal-sized eyes arranged in 3 pairs (most spiders have 8 eyes). The Ticks page lists its own marks.

See what's really crawling, flying, and buzzing past.

Start with a single photo.