Red Spiders: Identification, the Woodlouse Spider, and Which Ones Bite

First, is it a mite or a spider?

Both are arachnids and both have eight legs, so leg count will not settle it. Size does. Mites and spiders differ by roughly an order of magnitude, and that gap is visible without a lens.

If yours is a speck rather than a shape, it is a mite, and tiny red bugs covers clover mites, chiggers, and velvet mites in full. The rest of this page is about the spiders.

How to identify a red spider in five seconds

Work down this list in order. The first line that matches usually gives you the answer, because the red spiders people actually meet look nothing like each other once you know what separates them.

The red spiders that genuinely are spiders

Few spiders are truly red. Most are brown with a reddish cast, which is why so many sightings get reported as red. These are the ones that really do read as red, with the feature that identifies each.

Only two on that list carry venom that matters to people, and both are geographically restricted. The red widow lives in a narrow band of Florida scrub. The redback is Australian. For the widow you are far more likely to meet, see black widow identification.

Which red spider made this web?

Often the web is easier to find than the spider, and it narrows things faster than colour does. Web shape is also stable, so it works even when the animal has run off. Match what you can see to this table.

Two entries there rule things out quickly. A tidy circular orb never belongs to a woodlouse spider, because that species builds no catching web at all. Similarly, silk on plant leaves rather than in the air means mites rather than spiders every time.

The woodlouse spider, the one you probably found

Turn over a stone, a log, or a damp plant pot and you may meet a striking red-and-cream spider. That is almost certainly Dysdera crocata. It is the most commonly encountered red spider in North America and Europe, and it looks alarming for a reason that has nothing to do with people.

What a woodlouse spider looks like

• The fangs are the giveaway. They are disproportionately long and point forward rather than down. Arachnologists call them chelicerae, and this pair is specialised equipment for piercing the armoured shell of a woodlouse.
• Six eyes, not eight. They sit in a tight oval group. Only a few families share that arrangement, and it is the detail that starts the brown recluse confusion below.
• Colour split. Deep red-orange front section and legs, glossy pale cream or yellowish abdomen. Nothing else common looks like that.
• Size. Females run 11 to 15 mm in the body, males a little smaller at 9 to 10 mm. With legs out, a big female covers a coin.
• It builds no snare web. It hunts at night on foot and rests by day in a silk sac under stone or bark.

Where woodlouse spiders live, and what they eat

Look under stones, logs, loose bark, paving slabs, and plant pots. Anywhere damp with a supply of woodlice will do. The species is common across North America and Europe, and people have carried it to Australia, New Zealand, South Africa, and parts of South America.

Woodlice make up most of the diet, hence the name, but it is not fussy. Earwigs, millipedes, and silverfish all get taken. Indoors it turns up in cellars, garages, and ground-floor rooms with damp corners, which is exactly where woodlice gather too. So a woodlouse spider in the house is usually telling you something about moisture rather than about hygiene.

Eggs, young, and lifespan

The female lays roughly 70 eggs in a silk sac, tucked into her retreat under a stone or a log. Then she does something unusual for a spider. Instead of leaving, she stays with the spiderlings and guards them, and the young can take well over a year to reach maturity.

Adults live around three to four years, which is long for a spider this size. Mating is notably rough, with both sexes using those large fangs during the encounter. Birds and larger spiders are the main predators.

The other names people use

You will see this spider called the woodlouse hunter, the sowbug killer, the sowbug hunter, the pillbug hunter, and the slater spider. Every one of those names points at the same thing, which is what it eats. The family is Dysderidae, a small group of six-eyed hunting spiders.

Woodlouse spider vs brown recluse, the confusion that matters

This is the most important comparison on the page. In the United States the woodlouse spider, the red spider people meet most, is routinely mistaken for the brown recluse, and that mistake has real consequences. People pursue aggressive medical treatment for a bite that needed none.

The confusion starts with one genuine shared feature. Both species have six eyes instead of the usual eight, and six eyes is the classic field mark people are taught to check for recluses. Everything else about the two is different, though, and the differences are easy to see.

Note the range line, because it does more work than any other. Brown recluses live in a well-defined region of the south-central United States. Outside it, verified recluse sightings are genuinely rare, and researchers have repeatedly shown that reported recluse bites far outnumber the spiders. Consequently a red-and-cream spider found under a plant pot in Oregon or Maine is not a recluse.

For the full picture on the species people are actually worried about, see our brown recluse identification guide.

Do woodlouse spiders bite?

Yes, they can, and the fangs are certainly capable of piercing skin. The question people really want answered is whether it matters, and on that there is unusually good evidence for a spider this obscure.

A 2006 review in the journal Toxicon gathered 16 verified bites, meaning cases where the spider was caught and identified rather than guessed at. The findings were consistent. Pain was minor and typically lasted under one hour. Researchers attributed most of it to the mechanical puncture rather than to venom. Every lesion healed completely, with no necrosis and no secondary problems in any case.

The authors made the practical point directly. Documenting how mild these bites are may prevent unnecessary and potentially harmful treatment, because patients who believe a recluse bit them sometimes receive far more intervention than they need.

One more thing is worth knowing. The spider bites defensively, so a bite means it was pressed against skin, trapped in clothing, or picked up. Leave it room and it will walk away.

The red house spider, the one that is actually indoors

If your red spider is inside and sitting in a messy web, it is probably not a woodlouse spider at all. Nesticodes rufipes, the red house spider, is the species that genuinely lives indoors, and it looks quite different.

• All one colour. Reddish-brown over the whole body, legs included. There is no two-tone split, which separates it from the woodlouse spider instantly.
• Round abdomen. A globe-shaped rear end, glossy, sometimes with faint spots.
• Size. Body around 5 to 8 mm in females. Males are smaller with a leg span about half.
• Tangled web. A messy, three-dimensional cobweb anchored to walls and floors at several points. It is not a neat circular orb.
• Where indoors. Closet corners, cupboards, pantries, doorframes, and any dark undisturbed corner. Outside it uses siding corners, foundations, and leaf litter.

Where it lives and what it eats

In the United States it concentrates in the warm states, mainly Texas, Florida, and California, though it occurs worldwide. It breeds year round in warm conditions, and females make round egg sacs placed near the web rather than fixed onto it. Its diet is the reason it moved in: ants, houseflies, larder beetles, and whatever else walks through.

Bites are uncommon and not medically significant. Since the spider only bites when handled, the removal steps further down this page are all you need. To stop them returning, reduce the insects they hunt, clear clutter from dark corners, and seal gaps around doors and window frames. Our common house spider guide covers indoor spiders more generally.

Red jumping spiders, the bright scarlet ones

If your red spider moved in short darting hops, watched you, and built no web, it is a jumping spider. Three North American species read as properly red, and all three are harmless.

The cardinal jumper is the one worth a second look, because its colour is borrowed. It appears to mimic a velvet ant, which is a wingless wasp carrying a famously painful sting. Predators that have learned to leave velvet ants alone leave the spider alone as well. The scarlet is a warning signal it has no way of backing up.

The red-backed jumping spider is the one most western readers will meet, since it is among the largest and most commonly seen jumpers in western North America. It is reported to be bolder than most jumping spiders, but a bite still needs handling and produces nothing worse than brief local swelling. Our jumping spider guide covers the family in full.

Red orbweavers and sheetweavers

Two more red spiders turn up often enough to be worth naming, and both are found by their webs rather than by the animal.

Blacktailed red sheetweaver

Florinda coccinea, sometimes called the red grass spider, is bright red and only 3 to 4 mm long, with a small black spike at the rear end. It is common across the southeastern United States in lawns, grassland, and farm fields.

Its web explains most sightings. The spider spins a horizontal sheet of non-sticky silk with a tangle of threads above it. Flying insects hit the upper threads, drop onto the sheet, and get taken from below. On a dewy morning a lawn can show hundreds of these sheets at once, which is when people notice the spiders and start searching.

Spinybacked orbweaver

Gasteracantha cancriformis is the small crab-shaped spider with six spines around a hard abdomen. Females measure 5 to 9 mm long and are wider than they are long, at 10 to 13 mm across. In Florida the usual form is white with black spots and red spines, which is what puts it in a red spider search.

It builds a neat circular orb web, often at head height between shrubs, and it is completely harmless. Males are tiny at 2 to 3 mm and look almost like a different animal. You will also see a smaller red orbweaver, Hypsosinga rubens, reported in gardens, though it is far less often recorded.

The giant orange and yellow orbweaver in the same southern gardens is a different spider again. That one is the golden silk orb-weaver, which our guide to the banana spider covers. For the orb weaver family as a whole, including the spinybacked orbweaver’s other color forms, see our orb weaver identification guide.

The venomous red spiders, and where they actually live

Two red spiders carry venom worth respecting. Neither is likely to turn up in your house, and one of them has never been recorded biting a person at all.

Red widow

Latrodectus bishopi has orange-red legs and front section with a black abdomen marked by red spots ringed in white. It lives only in Florida sand-pine scrub, running from the Ocala National Forest down to Palm Beach County, plus one isolated population near Cedar Key.

Its web placement explains why nobody gets bitten. The spider rolls a palmetto frond into a cone, ties it with silk, and lives inside, usually a few feet off the ground in scrub that most people never walk through. Laboratory work confirms the venom is potent in the way other widow venoms are, yet there are no records of bites on humans.

Redback spider

Latrodectus hasselti is the Australian relative of the black widow, black with a bold red stripe down the back of the abdomen. Females run about 10 mm. Its bite is medically significant and an antivenom exists, so bites there are treated seriously.

The only reason it belongs on a North American page is that photographs of it circulate widely online, so people match their find to the wrong picture. Redbacks do not live in North America or Europe. If you are reading this from either place, what you found is something else.

So are red spiders dangerous?

For anyone in North America or Europe the practical answer is no. The red spider you are most likely to meet is the woodlouse spider, and the published evidence puts its bite at under an hour of minor pain. The red house spider is not medically significant. Every red jumping spider, sheetweaver, and orbweaver on this page is harmless.

The genuinely venomous red species live in habitats most people never enter, and the redback is on another continent. Meanwhile the thing most people are actually frightened of, the brown recluse, is not red and does not look like any spider above.

Two habits keep it that way. Never press a spider against your skin, since that is how nearly all defensive bites happen. Lift stones and logs from the far edge so your fingers stay out of the space underneath. To move one indoors, slide a card under a cup rather than using your hands.

First aid for a red spider bite

Almost nobody needs this section, but it is short and worth knowing. The steps below suit any bite from the harmless species on this page, which means every red spider in North America and Europe apart from the red widow.

1. Wash it with soap and water. This matters more than anything else, because ordinary skin bacteria cause far more trouble than spider venom does.
2. Apply something cold. A cool cloth or a wrapped ice pack for ten minutes brings down swelling and dulls the sting.
3. Take a plain painkiller if you want one. Paracetamol or ibuprofen handles the soreness. Most woodlouse spider pain is gone inside an hour anyway.
4. Leave it uncovered and do not scratch. Scratching breaks the skin and invites infection, which is the only realistic complication here.
5. Photograph the spider if you still have it. A clear picture settles the identification far better than the mark on your skin does.

One thing not to do is treat a bite as a recluse bite on suspicion. That mistake drives real overtreatment, and the comparison table further up this page exists to prevent it.

Red spiders by US region

Where you are narrows the list quickly, because several of these species have tight ranges. Find your region and start with the species listed for it.

When red spiders come indoors, and where they show up

Red spiders do not invade. They arrive one at a time, usually because the weather pushed them or because something they eat is already inside. Knowing the season narrows the answer almost as well as knowing the shape does.

Where they turn up inside is just as predictable:

• Cellars, garages, and ground-floor corners. Damp, cool, and full of woodlice, so this is woodlouse spider territory.
• Bathrooms and utility rooms. Same reason. Spiders do not climb up plugholes, despite the story. They fall into smooth basins and cannot climb out.
• Cupboards, pantries, and doorframes. Dry, undisturbed, and quietly full of small insects, which suits the red house spider.
• Sunny window sills and brickwork. Clover mites, every time. These are mites, so nothing needs killing.
• Plant pots brought in for winter. A classic way to import a woodlouse spider without noticing.

Because damp is the common thread, drying a space out does more than any spray. Fix the moisture and the woodlice leave, and the spider that came hunting them leaves with its food supply.

If it is a tiny red speck instead

Most searches for a tiny red spider turn out to be mites, and the usual answer is the clover mite at about 0.75 mm. It has one very long forward pair of legs that reads as antennae, gathers on sunny sills and brick in spring and autumn, and leaves a red smear if crushed. That smear is plant pigment rather than blood.

Clover mites do not bite. Red specks leaving itchy welts around sock and waistband lines mean chiggers instead, which are a different animal entirely. Tiny red bugs separates all of them by size, place, and whether they bite. For red mites on plant leaves with fine webbing, see spider mites, which are Tetranychus urticae and are plant pests rather than spiders.

Red spider myths, and what is actually true

Pest control disclaimer. Photo-based identification can help, but it is not always perfect. For dangerous spiders, large infestations, or anything you are unsure about, contact a licensed pest control professional.