The Long-Legged Spider in the Corner of the Ceiling
By IdentifyThese Editorial · Reviewed · 3 min read
The spider almost everyone has in the corner of a ceiling is a cellar spider, and it is one of the more interesting animals in a house.
Recognising it
A body only three to eight millimetres long, pale grey or tan, with legs several times the body length and so thin they are hard to see against a wall.
It hangs upside down in a loose, untidy, three-dimensional tangle of web with no pattern to it.
Approach it and it whirls — vibrating so fast that it becomes a blur. Nothing else common indoors does this, and it identifies the group immediately.
Not a harvestman
The name "daddy long-legs" is applied to at least three unrelated animals, which is where most of the confusion begins.
A cellar spider is a true spider: two body sections, eight eyes, silk, venom. A harvestman is an arachnid but not a spider — one fused body section, two eyes, no silk, no venom glands at all. Crane flies are insects with six legs.
The persistent claim that they are the most venomous spider in the world but cannot bite through skin fails on both halves, and is dismantled in the daddy long-legs myth.
| Cellar spider | Harvestman | Crane fly | |
|---|---|---|---|
| Body sections | Two | One | Three, winged |
| Legs | Eight | Eight | Six |
| Web | Yes, tangled | No | No |
| Where | Ceilings, cellars, indoors | Outdoors, under things | Flying, near lights |
What they do
Cellar spiders eat other spiders, and they are unusually good at it.
A cellar spider will invade another spider's web, mimic the vibrations of trapped prey, and attack the resident as it approaches. They take house spiders and, where they overlap, they take widows.
That makes them one of the few animals in a house whose presence measurably reduces the population of the species people actually worry about.
The webs
Untidy and permanent. Cellar spiders do not rebuild daily as orb weavers do; they add to the same tangle indefinitely.
That is why corners accumulate dusty webbing over months. The dust is not a sign of an abandoned web — the spider is often still in it, and the accumulated silk is doing its job.
Web type is a reliable identification route generally, and the comparison is in identifying a spider by its web.
Whether to remove them
They are harmless, they eat pests and other spiders, and they stay out of the way.
Removing the webs is reasonable for appearance. Removing the spiders means the house spiders and any widows in a garage have one fewer predator, which is a genuine trade rather than a rhetorical one.
If they need to go, the method in getting spiders out alive works — they are slow, fragile and easy to catch.
Numbers
A basement or garage can hold a great many, and they tolerate each other's presence more than most spiders do.
That is not a sign of anything wrong with the building. It reflects stable temperature, low disturbance and a supply of insects, and it is the normal state of an undisturbed cellar.
Where they concentrate
Cellars, garages, crawlspaces, undisturbed corners, and the space behind furniture — anywhere with stable temperature, low airflow and something for the web to span.
They also do well in bathrooms and around window frames, which is why the corner above a shower is such a reliable place to find one.
The species
Several are common indoors, and the differences are minor from a household point of view. Pholcus phalangioides is the widespread cosmopolitan one, and short-bodied relatives with a rounder abdomen turn up in the same places.
None of them differ in behaviour, diet or risk, so identifying to species is a matter of curiosity rather than of consequence.
Species referenced
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.
Keep reading
- The Daddy Long-Legs Myth, and the Three Animals It Refers ToThe claim that daddy long-legs have the world's most powerful venom but fangs too short to bite is wrong twice over — and it is applied to three completely different animals.
- Identifying a Spider by Its WebWeb architecture is fixed by family, so the web identifies the group even when the spider is hidden. Four shapes cover almost everything you will find.
- Black Widow or Common House Spider? Look UnderneathWidows and house spiders build the same messy web in the same dark corner. The red hourglass underneath is the whole test — plus three backup checks including the egg sac.