Several common spider species are white or pale enough to catch your eye, and nearly all of them are harmless. The most likely candidate you spotted is either a crab spider, a ghost spider, or a yellow sac spider, depending on where you found it and what it was doing. Here’s how to tell them apart and what to expect if one bites you.
Crab Spiders: The Most Common White Spider
The goldenrod crab spider is the species most people picture when they think of a white spider. These small, stocky spiders sit motionless on flowers with their front legs spread wide, waiting to ambush pollinators like bees and butterflies. They don’t build webs. Instead, they rely on camouflage, and they’re remarkably good at it.
What makes crab spiders unusual is their ability to change color. They secrete a yellow pigment into the outer cells of their body when sitting on yellow flowers, then slowly excrete that pigment when they move to a white flower. The shift from yellow to white takes about six days. On a white daisy or Queen Anne’s lace, they can be nearly invisible. Their bodies are broad and flattened, with legs that angle outward like a crab’s, which is how they got their name.
Crab spiders pose no threat to humans. Their venom is designed for insects, and their fangs are too small to cause meaningful harm to people.
Ghost Spiders
Ghost spiders are pale, fast-moving spiders you might find indoors or under leaf litter outside. They’re nocturnal hunters that spend the day tucked inside silken retreats they spin under leaves, rocks, or in quiet corners of your home. At night, they come out to chase down prey on foot rather than trapping it in a web. They’re among the fastest-running spiders you’ll encounter in a house.
Physically, ghost spiders are small and slender with a translucent, pale body that gives them their name. All eight of their eyes are round, and the central pair near the front of the head is noticeably smaller than the others. They look similar to sac spiders but tend to be more active and athletic. During mating season, males vibrate their abdomens so rapidly the movement becomes a blur.
Ghost spider bites are not medically significant. You’re unlikely to be bitten at all unless you accidentally press one against your skin.
Yellow Sac Spiders: Pale, Common, and Bitey
Yellow sac spiders are light yellow to cream colored, sometimes with a faint greenish tinge on the abdomen. They’re pale enough that many people describe them simply as “white spiders,” especially when spotted on a white wall or ceiling at night. Two species are widespread: one lives primarily outdoors on foliage, and the other is found almost exclusively inside homes, where it lays its eggs indoors year-round.
These are the spiders most likely to actually bite you. Yellow sac spiders probably account for more human bites than any other spider species. They’re active hunters that roam at night, and bites typically happen when a spider gets trapped between your skin and bedsheets, clothing, or shoes. The bite itself feels like a sharp sting and usually produces a red, swollen area that resolves on its own. Healthcare providers sometimes misdiagnose these bites as brown recluse bites, but yellow sac spider venom is far less dangerous.
White-Tailed Spiders
If you’re in Australia, the white spider you noticed may be a white-tailed spider. These are dark-bodied spiders with a distinctive white or cream-colored spot on the tip of the abdomen. They’re active hunters that prey on other spiders, often entering homes in search of them.
White-tailed spiders have a fearsome reputation in Australia, long blamed for causing severe skin ulcers and tissue death around the bite site. The evidence doesn’t support this. A prospective study published in the Medical Journal of Australia tracked 130 confirmed white-tailed spider bites over three years, with every spider caught and identified by an expert. Not a single case produced a necrotic ulcer. The most common outcome was a painful red mark lasting less than 24 hours (35% of cases) or a persistent irritated red lesion (44%). Pain occurred in every case and was severe in about a quarter of patients. Lab studies of the venom confirmed it has little ability to damage human cells and lacks the specific enzymes found in spiders that genuinely cause tissue death. Previous reports of ulcers were likely caused by bacterial infections or other conditions that were incorrectly blamed on the spider.
What to Do if a White Spider Bites You
For the vast majority of white or pale spiders, a bite is a minor event you can treat at home. Clean the area with mild soap and water, then apply a cool compress for about 15 minutes each hour to bring down swelling. Over-the-counter pain relievers help with discomfort, and an antihistamine can take care of itching. Keep the bite clean and watch it over the next day or two for signs of spreading redness or infection.
If the bite area blisters, keeps expanding, or you develop symptoms beyond the bite site (fever, chills, muscle aches), that’s worth a visit to urgent care. These symptoms are rare with the species described above but can indicate a secondary infection or, in unusual cases, a bite from a spider you didn’t get a good look at.
Telling White Spiders Apart
- Sitting still on a flower with legs spread wide: Almost certainly a crab spider. Stocky body, no web, front legs much longer than back legs.
- Running quickly across a wall or ceiling at night: Likely a ghost spider or yellow sac spider. Both are pale and slender. If it has built a small silk tube or sac in a corner, it’s probably a sac spider.
- Dark body with a white spot on the tail (Australia): White-tailed spider. The white marking is only at the tip of the abdomen, not the whole body.
- Round, nearly transparent body in a garden: Could be a young crab spider or one of many small orb-weaver species that appear whitish. If it’s sitting in or near a web, it’s an orb-weaver.
If you can, take a photo before the spider moves on. Size, body shape, and where you found it are usually enough to narrow down the species. Nearly every white spider you’ll encounter in North America, Europe, or Australia is harmless, and the few that bite produce symptoms no worse than a bee sting.