Cellar Spider: Daddy Long-Legs Identification and Habits (original) (raw)
The Cellar Spider (Pholcus phalangioides) is the spindly, long-legged spider you find hanging upside-down in messy webs on basement and garage ceilings across most of the world. Confusingly, it shares the nickname Daddy Long-Legs with two completely unrelated animals (harvestmen and crane flies), and it is at the centre of a popular myth about being “the most venomous spider in the world.” This guide covers what a Cellar Spider actually is, how to identify it, what it does, and what the venom story is really about.
Quick identification: is this a Cellar Spider?
- Tiny pale body, 6-10 mm long, usually pale tan, grey or yellowish.
- Extremely long, thin legs, often six to eight times the body length. Total leg span can exceed 50 mm on a tiny body.
- Hangs upside-down in a loose, tangled, three-dimensional cobweb in the corner of a ceiling, in a garage, or in a basement.
- Vibrates rapidly when disturbed, blurring itself to deter predators. This “whirling defence” is unique enough to identify the species on its own.
- Cylindrical, segmented abdomen, often with faint darker markings down the upper midline.
- Eight eyes in two clusters of three plus a separate pair (a classic Pholcidae arrangement). Hard to see without a hand lens.
“Daddy Long-Legs” can mean three different things
Before going further, it is worth clearing up a confusion that runs through almost every conversation about Cellar Spiders. The name “Daddy Long-Legs” is used in different countries for three different animals:
- Cellar Spider (Pholcus phalangioides and family Pholcidae). This is a true spider with eight legs, fangs, silk and venom glands. The subject of this guide.
- Harvestman (order Opiliones). Not a spider. Eight legs but a single fused body, no silk, no fangs and no venom glands. Often found in gardens, on tree bark, or in damp leaf litter, never in a web.
- Crane fly (family Tipulidae). Not a spider at all. A flying insect with six legs that is mistaken for a giant mosquito.
Throughout this article “Daddy Long-Legs” refers to the Cellar Spider unless otherwise stated.
Anatomy
Body and legs
The Cellar Spider has a small, pale body divided into the usual two spider segments: the cephalothorax at the front and a longer cylindrical abdomen at the back. The body alone is barely fingernail-tip-sized. What makes the species unmistakable is the legs: each leg is around 25 to 50 mm long, far longer than the body, and they are extremely thin and translucent. The legs have a characteristic articulated look, almost like four pairs of bent twigs. Leg pairs I and IV are the longest.
Eyes
Cellar Spiders have eight eyes arranged in two side clusters of three plus a small forward-facing pair. The arrangement is diagnostic but only visible with a magnifying lens or a sharp close-up photo, since the eyes are tiny.
Fangs and venom apparatus
Cellar Spiders are true spiders, with chelicerae (jaw segments) holding small downward-pointing fangs and a pair of venom glands behind them. The fangs are very short, around 0.25 mm. Compared to a fang of a brown recluse or black widow, a Cellar Spider’s fangs are barely capable of breaking human skin under most circumstances. The venom is real but the dose is tiny.
Where they live
Cellar Spiders prefer cool, dim, humid indoor spaces. The species is named for the most reliable habitat: cellars and basements. They are also extremely common on garage ceilings, in attics, in laundry rooms, in stairwells, and in any quiet corner of a house with low foot traffic. In warmer climates they live outdoors under sheltering rocks, beneath decks, in wood piles, and in cave entrances. The species is now found on every continent except Antarctica, having been spread by human commerce since the 1800s.
You usually find them by spotting their webs first. The webs are messy, low-tension, irregular three-dimensional cobwebs strung in ceiling corners or along beams. They are not pretty. They look unkempt and they collect dust readily.
Behaviour and the famous whirling defence
The Cellar Spider’s most striking behaviour appears the moment you disturb it. When threatened, the spider grips its web with its legs and rotates its body in tight circles at high speed, blurring itself out of focus. The effect, sometimes called the “whirling defence” or “blur defence,” is dramatic and unique: a spider that was clearly visible a second ago becomes a smear of motion, and any predator that targeted the original visual outline now has nothing to grab.
Cellar Spiders also have a remarkable diet for such a fragile-looking animal. They are confirmed predators of other spiders, including species considered dangerous to humans. They will invade the webs of larger spiders, vibrate the silk to mimic struggling prey, and ambush the resident spider when it comes to investigate. Documented prey includes Giant House Spiders, Hobo Spiders and even Black Widows. From a household pest-management perspective, this makes Cellar Spiders one of the more useful species you can have in a basement.
Are Cellar Spiders dangerous? The venom myth
You will eventually encounter the claim that Cellar Spiders, or Daddy Long-Legs, are “the most venomous spider in the world but their fangs are too short to bite a human.” The claim is one of the most widely repeated pieces of misinformation about spiders, and it is wrong on both counts.
- The venom is not unusually potent. Cellar Spider venom has been studied directly. It contains the typical insect-targeting peptides found in many spider venoms and is not exceptionally toxic to humans or to mammals more generally.
- The fangs can pierce human skin. The MythBusters television programme demonstrated this on camera. The bite produces only a brief, mild burning sensation. There is no significant medical effect.
- No verified case of medically significant Cellar Spider envenomation in humans exists. The species is genuinely harmless.
Where the myth comes from is unclear. The most likely origin is conflation with harvestmen, which are unrelated to spiders, share the “Daddy Long-Legs” nickname, and have no venom glands at all. Somewhere along the chain of folklore the two animals got merged into a single fictional creature with maximum venom and minimum delivery, and the story stuck.
Cellar Spider vs Other Long-legged Species
- Harvestman: single fused body (no waist), no web, eight legs, often dark brown or black. Found outdoors. Not a spider.
- Crane fly: flying insect with six legs and visible wings. Often mistaken for an oversized mosquito. Not a spider.
- Marbled Cellar Spider (Holocnemus pluchei): close relative of the common Cellar Spider with a more visibly marked body. Same family, same habits.
- Hobo Spider: brown, body 8-15 mm, builds a flat funnel web at ground level. See full guide.
Frequently Asked Questions
Do cellar spiders bite?
Cellar spiders very rarely bite humans. Their fangs are small and weak, and they’re not aggressive. Even in the rare event of a bite, the venom is harmless to people and typically causes nothing more than a mild, brief sting (if anything at all). The popular myth that they have “the most venomous venom in the world but fangs too short to pierce human skin” has been debunked.
Do cellar spiders eat woodlice?
Yes, cellar spiders will eat woodlice if they wander into their webs, though woodlice aren’t their preferred prey. Cellar spiders mainly feed on flies, mosquitoes, moths, ants, and other small insects. They’re also famous for eating other spiders, including larger species like house spiders and even hobo spiders.
Are cellar spiders dangerous?
No. They’re harmless to humans and pets. In fact, they’re considered beneficial because they hunt pests and other unwanted spiders.
Why are they called “daddy long legs”?
Their long, spindly legs earned them the nickname, but it’s confusing because the term “daddy long legs” is also used for harvestmen (which aren’t spiders) and crane flies (which are insects). True cellar spiders belong to the family Pholcidae.
Where do cellar spiders live?
As the name suggests, they love cellars, basements, garages, attics, sheds, and the corners of quiet rooms. They prefer dark, damp, undisturbed spaces where they can build messy, irregular webs.
Why do cellar spiders shake or vibrate when disturbed?
This behavior is called “whirling” or “wobbling.” When threatened, they spin rapidly in their web to become a blur, making it harder for predators to target them. It’s a defense mechanism, not a sign of aggression.
How long do cellar spiders live?
Most live around 1–2 years, which is unusually long for a spider. Females can lay multiple egg sacs during their lifetime, carrying them in their jaws until the spiderlings hatch.
Do cellar spiders make messy webs?
Yes. Their webs look tangled and unstructured rather than the neat spiral webs you’d see from orb weavers. They don’t clean up old webs, so cobwebs accumulate quickly in untreated areas.
How do I get rid of cellar spiders?
The simplest method is regular vacuuming of webs, egg sacs, and spiders themselves. Reduce humidity with a dehumidifier, seal cracks around windows and doors, and remove clutter where they can hide. Many people choose to leave them alone since they control other pests.
Are cellar spiders the same as brown recluses?
No, and this is a common mix-up. Brown recluses have a distinctive violin-shaped marking and a much more compact body. Cellar spiders have tiny bodies with extremely long, thin legs, and they’re harmless.
Do cellar spiders eat their own kind?
Yes, cellar spiders are known to be cannibalistic, especially when food is scarce. They’ll also invade other spiders’ webs to eat the resident spider.
Related Guides
- Hobo Spider identification guide and quiz
- Spiders in North America
- Black Widow Spider
- Spider anatomy diagram
Cite This Page
APA
(2026, April 29). Cellar Spider (Daddy Long-Legs). Animal Corner. Retrieved 2026, May 17, from https://animalcorner.org/animals/cellar-spider/
MLA
. "Cellar Spider (Daddy Long-Legs)." Animal Corner, 2026, April 29, https://animalcorner.org/animals/cellar-spider/.
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