Spiders in Utah
Utah is within the range of desert recluse. Widow species present: western black widow.
Medically significant spiders in Utah
The only species here whose bite might need a doctor. Both groups are shy and bite defensively rather than aggressively.
Harmless spiders in Utah
Far more common, and the source of nearly every alarmed spider report.
Pale yellow, cream or faintly greenish, with conspicuously darker brown mouthparts and often dark feet.
Robust, hairy and heavily patterned in brown and grey, usually with lengthwise stripes on the head-and-thorax and chevron markings on the abdomen.
Medium brown with a pattern of pale chevrons pointing forward along the abdomen, and — critically — plain, unbanded legs with no dark rings..
Brown with two bold dark lengthwise stripes on the head-and-thorax, and a pair of long, finger-like spinnerets projecting visibly from the rear of the abdomen..
Dull tan to grey-brown with a high, rounded, mottled abdomen patterned in darker smudges, and faintly banded legs.
Dark purplish-brown to near black with a slightly glossy, bulbous abdomen, often with faint pale crescent markings near the front.
Pale tan or grey with a long, narrow, cylindrical abdomen and extremely long thin legs.
A single small oval body with no visible waist, carried on eight extremely long thin legs.
Bold black-and-yellow patterned abdomen, silvery head-and-thorax, and black legs with orange or yellow bands near the body..
A strikingly round abdomen, bright orange or creamy yellow with a marbled pattern of dark brown or purplish markings.
Fuzzy black body with a triangular white spot and two smaller spots on the abdomen, and brilliant iridescent green or blue-green fangs.
Small and boldly striped in black and white, with the characteristic jumping-spider face: two large forward eyes and a squared-off head..
Large, flattened and mottled grey-brown with dark chevrons pointing forward on the abdomen and boldly banded legs.
Slender tan or straw-coloured body with a broad dark stripe running the length of the back, edged in cream.
Squat crab-like body, pure white or bright yellow, often with a pair of red streaks along the sides of the abdomen.
Unmistakable: a glossy orange-red head, thorax and legs with a smooth, shiny cream or pinkish-grey abdomen, and enormous forward-projecting fangs..
Identify what you found in Utah
Already filtered to Utah. Add the web shape, size and markings to narrow it further.
1.Was there a web, and what shape?
optionalThe most informative question. Web architecture is fixed by family, so it separates the big groups immediately — and it rules out recluses and widows faster than anything else.
2.Which state are you in?
Matters more than you would expect. Brown recluses are absent from most of the country, including California, Florida and the entire northeast.
3.How big was the body?
optionalBody only, not counting the legs. Neighbouring sizes stay on the list, because everyone overestimates.
4.Where did you find it?
optionalIndoor and outdoor spiders barely overlap, so this cuts the list roughly in half.
5.Any distinctive markings?
optionalA red hourglass underneath means a widow and nothing else. A violin shape is suggestive of a recluse but far from conclusive — several harmless spiders have similar marks.
6.Did it do any of these?
optionalBehaviour separates families cleanly. Jumping means a jumping spider; eyes reflecting a torch beam means a wolf spider.
7.What colour was it?
optionalLast, and it never removes anything from the list — spider colour varies with age, moult stage and light.
- Desert RecluseSee a doctorLoxosceles deserta
- Western Black WidowSee a doctorLatrodectus hesperus
- American House SpiderHarmlessParasteatoda tepidariorum
- Black and Yellow Garden SpiderHarmlessArgiope aurantia
- Bold Jumping SpiderHarmlessPhidippus audax
- Dark Fishing SpiderHarmlessDolomedes tenebrosus
- False WidowStings onlySteatoda grossa
- Goldenrod Crab SpiderHarmlessMisumena vatia
- Grass SpiderHarmlessAgelenopsis species
- HarvestmanHarmlessOrder Opiliones
- Hobo SpiderHarmlessEratigena agrestis
- Long-bodied Cellar SpiderHarmlessPholcus phalangioides
- Marbled OrbweaverHarmlessAraneus marmoreus
- Nursery Web SpiderHarmlessPisaurina mira
- Wolf SpiderHarmlessTigrosa and Hogna species
- Woodlouse SpiderStings onlyDysdera crocata
- Yellow Sac SpiderStings onlyCheiracanthium inclusum
- Zebra Jumping SpiderHarmlessSalticus scenicus
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.