Why Spiders Come Inside
Despite common belief, most spiders found indoors didn't wander in from outside — many species have evolved to live alongside humans. Indoors offers a stable temperature, low humidity in some rooms, and an abundance of small insects to prey on. Understanding where different species prefer to live is a useful first step to identifying them.
Table of Contents
- Bathroom & Basement Spiders
- Living Room & Bedroom Spiders
- Garage & Shed Spiders
- Quick Identification by Web Type
- When to Be Concerned
1. Bathroom & Basement Spiders
Drain Spider / Cellar Spider (Pholcus phalangioides)
Long, spindly legs and a small, pale body — this is the spider most people find dangling in corners or near plumbing. Despite an urban myth, cellar spiders are not dangerously venomous; their small fangs cannot penetrate human skin effectively. They build loose, irregular webs and are harmless.
Funnel Web House Spider (Tegenaria / Eratigena spp.)
These large, fast-moving brown spiders are frequently found in baths and basins — they fall in while hunting and cannot climb the smooth sides. They build flat sheet webs with a funnel retreat. They are not dangerous and play a useful role catching other insects.
2. Living Room & Bedroom Spiders
Common House Spider (Parasteatoda tepidariorum)
A small, brownish spider with a round abdomen and tangled, cobweb-style webs in corners. One of the most widespread indoor spiders in North America. Completely harmless. Often seen suspended in messy webs in undisturbed corners.
Jumping Spider (Phidippus and related genera)
Compact, fuzzy, and often boldly patterned, jumping spiders are active hunters that don't use webs to catch prey. They have large forward-facing eyes and remarkable vision. Often seen moving across walls or window frames in daylight. Fascinating to observe and entirely harmless.
Sac Spider (Cheiracanthium spp.)
Pale yellow-beige spiders that build small silken sacs in corners or along wall-ceiling junctions. They are nocturnal hunters. In North America, some species can deliver a mildly irritating bite, though reactions are generally minor.
3. Garage & Shed Spiders
Garden / Cross Spider (Araneus diadematus)
Recognizable by the distinctive white cross-shaped pattern of dots on the abdomen. Builds classic orb webs. Often found near doors and windows where they can intercept flying insects. Harmless and highly beneficial.
False Black Widow (Steatoda grossa)
A dark, glossy, round-bodied spider sometimes confused with the black widow. Important distinction: false black widows have no red hourglass marking and are far less venomous. Their bite can cause localized pain but is not medically significant for most people. Found in garages, sheds, and dark undisturbed spaces.
Quick Identification by Web Type
| Web Type | Likely Spider | Location |
|---|---|---|
| Round orb web | Orb-weaver (Araneus spp.) | Windows, doorframes |
| Tangled cobweb | House spider, false black widow | Corners, behind furniture |
| Flat sheet with funnel | Funnel web house spider | Basements, garages |
| Loose, long-legged tangle | Cellar spider (daddy long-legs) | Bathrooms, ceilings |
| No web (active hunter) | Jumping spider, sac spider | Walls, floors |
When to Be Concerned
In the UK, Europe, and most of North America, the vast majority of house spiders pose no meaningful threat to human health. However, be aware of the following genuinely dangerous species in regions where they occur:
- Black Widow (Latrodectus spp.) — southern/western USA. Identifiable by the red hourglass marking on the underside. Seek medical attention if bitten.
- Brown Recluse (Loxosceles reclusa) — south-central USA. Violin-shaped marking on the cephalothorax. Bites can cause tissue necrosis in rare cases.
- Redback Spider (Latrodectus hasselti) — Australia. Red stripe on the abdomen.
If you suspect a bite from any of these species, seek medical advice promptly. For all other house spiders: observe, appreciate, and relocate gently if needed.