The short answer to whether a “daddy long legs” can bite a human is generally no, or that any bite is inconsequential and medically harmless. The confusion stems from the fact that the common name “daddy long legs” is used to describe at least two entirely different creatures, only one of which is a true spider. Understanding these separate groups—the Harvestmen and the Cellar Spiders—is necessary to determine their potential to bite or cause harm.
Unpacking the Confusion: Two Different Creatures
The popular name “daddy long legs” most commonly refers to two distinct types of arachnids: the Harvestmen (order Opiliones) and the Cellar Spiders (family Pholcidae). These two groups are easily differentiated by their anatomy. True spiders, like the Cellar Spider, have two distinct body segments—the cephalothorax and the abdomen—joined by a narrow stalk. Harvestmen, in contrast, possess only one fused, oval-shaped body section. Harvestmen also have only two eyes, while Cellar Spiders typically have eight. This difference in body structure directly influences their mouthparts and their capacity for biting.
Harvestmen: The Non-Biting Arachnid
Harvestmen are the creature most frequently associated with the “daddy long legs” name, and they are not spiders, though they are arachnids. They cannot bite a human with any measurable effect because they possess neither fangs nor venom glands. Their mouthparts, called chelicerae, are designed like small, segmented pincers for chewing food, not for piercing skin or injecting toxins. These creatures are primarily scavengers and omnivores, consuming small insects, decaying plant matter, and droppings. The structure of their mouthparts is made for tearing food into small pieces to ingest, not for aggressive hunting or defense. A Harvestman is physically incapable of inflicting a bite that would break human skin.
Cellar Spiders: The Truth About Their Fangs
Cellar Spiders are the second creature commonly referred to as “daddy long legs,” and they are true spiders, possessing fangs and venom glands. The myth that they are highly venomous but cannot bite due to short fangs is largely unfounded. Research indicates that their venom is relatively mild, suggesting it is only a fraction of the potency of a brown recluse spider’s venom. Their fangs are quite small, measuring only about a quarter of a millimeter in length. Since human skin thickness can vary from half a millimeter up to several millimeters, their fangs are too short to effectively penetrate the skin barrier and deliver venom. While a bite is possible under extreme duress, documented cases show the typical result is a mild, inconsequential sting with no lasting effects.