Spiny-backed Orbweaver
HarmlessGasteracantha cancriformis · also called crab spider (misapplied), spiny orbweaver, jewel spider
The spiny-backed orbweaver is one of the most distinctive spiders in North America and impossible to confuse with anything else once seen. It is tiny, brightly coloured, hard-shelled and completely harmless, and southern hikers walk through its webs constantly.
Quick facts
- Bite risk
- Harmless. The spines are structural, not venomous, and it cannot meaningfully bite.
- Size
- Body 5–10 mm. Small — the body is wider than it is long, roughly the width of a fingernail.
- Appearance
- A hard, flattened, wider-than-long abdomen — usually white or yellow with black spots — edged with six red or black spines. Looks more like a piece of enamel jewellery than an animal.
- Web
- Small orb web strung between shrubs and trees, often at face height across a path, with tufts of silk on the anchor lines.
- Found in
- garden, woods
- Family
- Araneidae
- Range
- 13 US states
How to identify a spiny-backed orbweaver
- Six sharp spines projecting from the edge of a hard, flattened abdomen.
- Wider than long — an unusual shape for any spider.
- Bright white, yellow or red with black spots.
- Small orb webs at head height across trails and between shrubs.
How it behaves
Sits in the middle of its web, rebuilding it regularly. Harmless and passive.
Where it lives
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.