The question of whether a “Granddaddy Long Legs” is poisonous is complicated by the fact that the name refers to at least two distinct types of arachnids, only one of which is a true spider. This common confusion has fueled a persistent urban legend about their danger. Understanding the biological differences between these long-legged creatures is the first step toward clarifying their threat level, which ranges from non-existent to medically insignificant.
Identifying the Granddaddy Long Legs
The colloquial term “Granddaddy Long Legs” is used to describe two groups within the class Arachnida: Harvestmen (order Opiliones) and Cellar Spiders (family Pholcidae). Harvestmen are easily distinguished because their body appears as a single, fused oval segment with no discernible “waist.” They possess eight legs but lack silk-producing spinnerets and venom glands entirely.
In contrast, Cellar Spiders are true spiders, featuring a distinct two-part body structure. They spin irregular, messy webs and possess both fangs and venom glands.
Harvestmen (Opiliones)
Harvestmen are arachnids that are often mistaken for spiders, but they pose no threat to human health. They do not possess the specialized glands needed to produce venom, making the premise of them being venomous unfounded in their biology. Instead of fangs, Harvestmen have chelicerae, which are small, pincer-like mouthparts used for chewing and grasping food. They are scavengers and predators that feed on small insects, dead organisms, and plant matter. When threatened, some species may release a foul-smelling chemical as a defensive mechanism, but this substance is harmless to people upon contact.
Cellar Spiders (Pholcidae)
Cellar Spiders are the true spider variety commonly called Granddaddy Long Legs. Like nearly all spiders, they possess venom glands and fangs. Their venom is neurotoxic, meaning it affects the nervous system of their insect prey, but it is weak and considered medically insignificant to humans. Research comparing the venom of a cellar spider to that of a black widow found the black widow venom to be much more potent.
The bite capability of a Cellar Spider is often questioned because their fangs are small and delicate, measuring around a quarter of a millimeter in some species. While the fangs may struggle to penetrate the relatively thick skin of a human, a bite is possible if the spider is squeezed or severely provoked. Documented bites on humans have consistently resulted in only a mild, localized sting with no lasting effects.
Persistent Misconceptions
The most enduring piece of folklore about Granddaddy Long Legs is the claim that they are the most venomous spiders in the world, but their fangs are too short to bite humans. This popular myth is biologically inaccurate on multiple fronts. The creature most often associated with the name, the Harvestman, lacks venom entirely.
The true spider counterpart, the Cellar Spider, does have fangs and venom, but the venom’s strength is minimal and poses no medical danger to humans. The belief that they are “the most dangerous” likely stems from the fact that Cellar Spiders are known to prey on other, more dangerous spiders, such as the Black Widow. In reality, the long-legged arachnids living in homes are universally harmless.