“Daddy long legs” and “cellar spider” are often used interchangeably, but they can refer to completely different creatures. The name “daddy long legs” is applied to at least three unrelated animals depending on where you live: harvestmen, cellar spiders, and crane flies. When most people search for this comparison, they’re trying to sort out the difference between harvestmen and cellar spiders, the two arachnids that share the nickname. Despite looking similar at first glance, one is a true spider and the other isn’t even close.
Three Creatures, One Nickname
The confusion starts with sloppy common naming. In the United States and UK, “daddy long legs” can mean any of the following:
- Harvestmen (order Opiliones): arachnids, but not spiders. This is the most traditional use of “daddy long legs” in North America.
- Cellar spiders (family Pholcidae): true spiders that build webs in dark corners of homes. Sometimes called “daddy longlegs spiders” to distinguish them.
- Crane flies (family Tipulidae): flying insects that look like oversized mosquitoes. This usage is most common in the UK.
Crane flies are insects with wings and six legs, so they’re easy to rule out. The real identity crisis is between harvestmen and cellar spiders, which both have tiny bodies and disproportionately long, thin legs.
How to Tell Them Apart
The single fastest way to distinguish a harvestman from a cellar spider is body shape. A cellar spider has two clearly separate body sections: a front segment (the fused head and thorax) connected by a narrow waist to a rounded abdomen. This two-part body plan is the hallmark of all true spiders. A harvestman’s body looks like a single oval pill. There’s no visible waist or separation between segments.
Eyes offer another clue. Harvestmen have just one pair of eyes, mounted on a small raised bump on top of their body. Cellar spiders, like most spiders, have multiple pairs of eyes clustered at the front of their head region.
Leg use is subtly different too. Harvestmen use their three rear pairs of legs for walking and hold their front pair out ahead of them like antennae, sweeping the ground for sensory information. Cellar spiders use all eight legs for gripping their web and walking.
Webs vs. No Webs
This is the most practical difference if you’re trying to identify what’s living in your basement. Cellar spiders spin webs. Their webs are loose, irregular, and messy, nothing like the neat spirals of an orb weaver. You’ll find them draped in ceiling corners, along joists, behind furniture, and in any undisturbed dark space. Over time, cellar spiders add new silk without removing the old, which is why their webs accumulate into those dusty, cobwebby tangles.
Harvestmen cannot make webs at all. They lack silk glands entirely. If you see a long-legged arachnid sitting in the middle of a web, it’s a cellar spider. If you see one wandering across a wall, the floor, or your porch railing with no web in sight, it’s likely a harvestman.
The “Most Venomous” Myth
You’ve probably heard the claim that daddy long legs are the most venomous spiders in the world but their fangs are too short to bite humans. This is wrong on multiple levels, and the confusion between these two creatures is partly to blame.
Harvestmen are not venomous at all. They aren’t spiders, they don’t have venom glands, and they don’t have fangs. The myth doesn’t even apply to them.
Cellar spiders do have venom and fangs. Their fangs are structurally similar to those of the brown recluse, so the “too short to pierce skin” claim doesn’t hold up either. Cellar spiders can bite humans, but the result is trivial. Rick Vetter, a well-known arachnologist at UC Riverside, has noted that the only documented reaction in a person was a small dark mark that disappeared within a couple of days. In a study based on a 2004 “MythBusters” experiment, researcher Charles Kristensen injected mice with cellar spider venom and black widow venom separately. The black widow venom was far more potent. Cellar spider venom is simply not dangerous to people.
The Whirling Defense
Cellar spiders have a distinctive behavior you won’t see in any other common household spider. When threatened, a cellar spider hanging upside down in its web will start rapidly whirling its body in a circle. It does this by flexing its legs in a wave pattern, successively lengthening and shortening each leg so that its body swings beneath the web like a pendulum. The motion blurs its outline, making it harder for a predator to pinpoint or grab. To a would-be attacker, the spider appears larger and less recognizable as prey.
Harvestmen have their own defenses. Many species can release foul-smelling chemical secretions from glands on their body. Some can also shed a leg when grabbed, leaving the twitching limb behind as a distraction while they escape. Unlike some lizards, harvestmen cannot regrow lost legs.
Diet and Ecological Role
Both creatures eat other small invertebrates, but they hunt in very different ways. Cellar spiders are web hunters. They’re highly sensitive to vibrations in their silk and can detect and wrap prey quickly. In homes, they catch flies, mosquitoes, and other small insects. They also prey on other spiders, including house spiders and, in some cases, even larger species that wander into their web.
Harvestmen are ground-level scavengers and opportunistic predators. They eat small insects, decaying plant material, fungi, and even dead animals. You’ll find them outdoors in leaf litter, under rocks, on tree trunks, and around porch lights where insects gather at night. They occasionally wander indoors but don’t establish themselves in houses the way cellar spiders do.
Living With Cellar Spiders Indoors
Cellar spiders are among the most common indoor spiders worldwide, and they’re genuinely useful. A cellar spider population in your basement or garage will reduce flies, wasps, and other pest spiders. They pose zero threat to people, pets, or property.
The tradeoff is aesthetics. Because cellar spiders never clean up old webbing, their webs accumulate into conspicuous, dusty sheets that make a space look neglected. If the webs bother you, knocking them down with a broom is the simplest approach. The spider will rebuild, but regular cleaning keeps things manageable. If you’d rather remove them entirely, reducing humidity and sealing entry points around windows and foundations will make your home less inviting. There’s no practical reason to use pesticides on cellar spiders.
Harvestmen, by contrast, rarely become indoor residents. If you find one inside, it probably wandered in through a door or window and will leave or die on its own without establishing a population.