The common name “Daddy Long Legs” creates widespread confusion because it refers to multiple distinct creatures across different regions. This shared, non-scientific label often leads to misunderstandings about whether the animal is a spider, a scorpion, or another kind of invertebrate entirely. Resolving this taxonomic ambiguity requires clarifying the three main organisms that share this moniker and detailing their specific biological differences. By examining their true scientific classifications, it becomes clear that these animals are not all closely related, despite their similar appearance of having small bodies and disproportionately long, thin legs.
The Creatures Behind the Name
The term “Daddy Long Legs” is used for three different types of invertebrates: the Harvestman, the Cellar Spider, and the Crane Fly. Only two of these are arachnids, the class that includes spiders, scorpions, and mites.
The creature most commonly called the Daddy Long Legs is the Harvestman (Order Opiliones), which is an arachnid but is not a spider. The Cellar Spider (Family Pholcidae) is a true spider, often found hanging in webs in basements and dark corners. The third organism is the Crane Fly (Family Tipulidae), a flying insect that is not an arachnid at all.
Key Anatomical Differences
The primary difference between a Harvestman (Opiliones) and a true spider (Araneae) is the structure of the body segments, known as tagmata. Spiders have two distinct body sections, a cephalothorax and an abdomen, joined by a narrow stalk called a pedicel. In contrast, the Harvestman’s body appears as a single, fused, oval-shaped structure because the juncture between the cephalothorax and the abdomen is broad and indistinct.
Harvestmen also differ in eye structure. While most spiders have eight simple eyes, Harvestmen usually have only two eyes, mounted on a small, elevated mound called an ocularium. Furthermore, Harvestmen lack the ability to produce silk, which is a defining characteristic of true spiders. They do not build webs for catching prey or for shelter.
The feeding appendages also show a clear distinction. Spiders use chelicerae that end in fangs to inject venom into their prey. Harvestmen have chelicerae that are more like small, pincer-like jaws, which they use to grasp and tear apart their food. Harvestmen are also omnivorous, consuming small insects, dead organic matter, and plant material, a feeding behavior uncommon among true spiders.
Settling the Venom Myth
A widespread urban myth claims that the Daddy Long Legs possesses the most potent venom in the world but is harmless because its fangs are too short to bite humans. This story is false and must be addressed separately for the two arachnids that share the common name.
Harvestmen (Opiliones) are not venomous at all because they completely lack venom glands in their chelicerae. They subdue their prey through physical means and are entirely harmless to humans. They do possess defensive scent glands that release a noxious fluid when disturbed.
The Cellar Spider (Pholcidae) is a true spider and therefore possesses venom glands and fangs. However, the venom is relatively mild and not medically significant to humans, debunking the myth of extreme potency. Cellar Spiders are capable of biting human skin, contradicting the claim that their fangs are too small. Documented bites typically result in a mild, temporary sting with no lasting effects. The Cellar Spider’s venom potency on insects is comparable to other spider venoms, but there is no scientific evidence to support the idea that their venom is uniquely deadly to mammals.