The common name “Daddy Long Legs” is a source of widespread confusion, as it is used to describe at least three different creatures, only one of which is a true spider. The term is most often applied to two distinct groups of arachnids that look superficially similar because of their elongated legs and small, oval bodies. Understanding the biological differences between these two groups, the Harvestmen and the Cellar Spiders, is the only way to resolve the identity crisis of the “Daddy Long Legs.” The classification depends entirely on specific anatomical features, such as the number of body segments and the presence of venom glands.
The Non-Spider Arachnid
The creature most commonly designated as the “Daddy Long Legs” in North America is the Harvestman, which belongs to the order Opiliones. While it is an arachnid, possessing eight legs, the Harvestman is not a true spider, being as distinct from a spider as a scorpion or a tick. This animal is easily identified by its body structure, where the cephalothorax and abdomen are broadly joined, making the body appear as one fused, oval segment. True spiders, by contrast, always have two distinct body sections separated by a narrow connection.
Harvestmen also lack the specialized biological features that define a true spider. They do not possess silk glands, meaning they are incapable of spinning webs to trap prey or to create retreats. Instead of being predators that inject venom, Harvestmen are primarily omnivores, feeding on small insects, decaying plant matter, and fungi. Their mouthparts are chelicerae that function as pincer-like jaws for grasping and chewing solid food.
Furthermore, these arachnids have a significantly different visual system compared to most spiders. The vast majority of Harvestmen species possess only two eyes, which are often mounted on a raised structure called an ocular tubercle on the back of their cephalothorax. When disturbed, some species can release a foul-smelling fluid from scent glands on their bodies as a defense mechanism against predators. This group of arachnids is generally found roaming freely on the ground, under stones, or in damp leaf litter, rather than hanging in webs.
The True Spider
The second creature frequently called a “Daddy Long Legs” is the Cellar Spider, which is definitively a true spider belonging to the family Pholcidae. These spiders are commonly encountered in basements, cellars, and dark corners of human dwellings, which is how they earned their alternate name. Cellar Spiders fit the established classification of the order Araneae because their body is clearly divided into two distinct parts: the cephalothorax and the abdomen.
Like all true spiders, the Cellar Spider possesses specialized structures, including chelicerae, which are equipped with fangs. These fangs are used to inject venom into their prey, confirming their status as predators. Cellar Spiders are also capable of producing silk from spinnerets located at the rear of their abdomen. They use this silk to construct the messy, tangled, and irregular cobwebs often seen in undisturbed areas of a home.
Many species of Cellar Spiders, such as the long-bodied variety, have eight eyes, though some genera within the family may have six eyes. When a threat or prey is detected, these spiders exhibit a characteristic behavior of rapidly vibrating or gyrating in their webs. This movement turns the spider into a blurry image, which is thought to confuse or deter potential predators or tangled prey.
Anatomical Differences That Define Them
The easiest way to distinguish between the two arachnids is by observing their body segmentation. The Harvestman has a body that appears to be a single, fused oval structure, with no visible waist or separation between the front and rear sections. In sharp contrast, the Cellar Spider displays the classic spider anatomy, featuring a clear constriction, or pedicel, that separates the cephalothorax from the bulbous abdomen.
Another reliable difference is the eye count and arrangement. Harvestmen typically have only two eyes, which are found close together on a small mound. Cellar Spiders, like most true spiders, generally have eight eyes, which are arranged in two distinct groups of three, with two smaller eyes in the center. The ability to spin a web is another definitive trait; if the long-legged creature is found resting in a silk web, it is a Cellar Spider, as Harvestmen do not produce silk.
The presence of fangs and venom further separates the two groups. Cellar Spiders possess fangs and venom glands, which they use for subduing prey, even though they are harmless to humans. Harvestmen lack both venom glands and true fangs, instead using a pair of small, pincer-like mouthparts to consume food. The difference in their feeding apparatus reflects their ecological roles, with the spider being a dedicated predator and the Harvestman being an omnivorous scavenger.
Addressing the Toxicity Myth
A persistent and widespread urban legend claims that the “Daddy Long Legs” possesses the most potent venom of any spider, but its fangs are too short to pierce human skin. This claim is completely unfounded, regardless of which long-legged arachnid is being discussed. The Harvestman, the non-spider arachnid, has no venom glands whatsoever and is therefore entirely non-venomous and harmless to people. The Cellar Spider, which is a true spider, does produce venom, as virtually all spiders do. However, the venom produced by the family Pholcidae is not considered medically significant to humans. Even if a bite were to occur, the effect is comparable to a minor sting. The myth likely gained traction because Cellar Spiders are known to occasionally prey on and kill other, more dangerous spiders, such as the Black Widow.