American House Spider
HarmlessParasteatoda tepidariorum · also called common house spider, cobweb spider
This is the spider responsible for most cobwebs in most houses. It is small, dull, entirely harmless, and it is the species most often mistaken for a widow because it builds the same kind of messy tangle web in the same kind of dark corner.
Quick facts
- Bite risk
- Harmless. Effectively incapable of a bite that matters.
- Size
- Body 4–8 mm. Body about a grain of rice to a small pea, with fine legs.
- Appearance
- Dull tan to grey-brown with a high, rounded, mottled abdomen patterned in darker smudges, and faintly banded legs. Never glossy.
- Web
- The classic dusty cobweb in a ceiling corner, behind a door, or in a window frame. Messy and three-dimensional.
- Found in
- indoors, basement, garage, bathroom
- Family
- Theridiidae
- Range
- Most of the United States
How to identify a american house spider
- Dull, matte, mottled appearance. Widows are glossy and look varnished.
- No hourglass anywhere on the underside.
- Round smooth tan egg sacs, not spiky ones.
- Hangs upside down in a messy tangle web indoors.
How it behaves
Sits in the web permanently and abandons old webs to build fresh ones nearby, which is why cobwebs accumulate.
What the american house spider is confused with
One observation settles each of these.
Widows are glossy jet black with a red hourglass underneath. House spiders are dull, mottled and have neither.
False widows are darker and glossier with a more purplish-brown abdomen, but still have no hourglass.
If you think you were bitten
- Most suspected spider bites are not spider bites. Studies of patients presenting with a “spider bite” repeatedly find that the large majority are bacterial skin infections — frequently MRSA — which need antibiotics rather than reassurance. A spreading, painful, pus-filled sore is far more likely to be an infection than a spider.
- Wash it, ice it, and watch it. Clean the area with soap and water, apply a cold pack, and keep an eye on it.
- Get medical care if the wound spreads or darkens, if you develop cramping, sweating, fever or severe abdominal pain, or if you are confident it was a widow or a recluse.
- Bring the spider only if it is already dead and to hand. Do not go looking for it. Doctors treat symptoms, not species.
In the US, the Poison Help line is 1-800-222-1222. This site is a reference, not medical advice.