The belief that “daddy long legs” are the most venomous spiders, yet harmless due to small fangs, is a persistent urban legend. This article clarifies the scientific truth and addresses common misconceptions. Understanding their biology demystifies their perceived danger.
Unpacking “Daddy Long Legs”
The term “daddy long legs” refers to two distinct arachnids: Harvestmen (Order Opiliones) and Cellar Spiders (Family Pholcidae). While both have long legs, they differ significantly. Harvestmen are arachnids, but not true spiders. Their bodies are a single, fused oval segment, unlike spiders with two distinct regions. Harvestmen typically have two eyes, while most true spiders have eight.
Harvestmen do not produce silk or spin webs, nor do they possess fangs. Instead, they have small, grasping mouthparts that resemble pincers, used for tearing apart prey or scavenging. They are omnivores, feeding on small insects, decaying matter, fungi, and plant material.
Cellar Spiders (Pholcidae) are true spiders. Like all spiders, they have two distinct body segments and typically eight eyes. They are known for their long, thin legs and for building irregular webs in dark, damp areas like basements. They are predatory, using webs to capture insects and other spiders.
The Venom Question
The key distinction for “daddy long legs” is venom. Harvestmen (Opiliones) do not possess venom glands and are not venomous. Their mouthparts cannot inject venom, making them harmless to humans. When threatened, harvestmen release a foul-smelling fluid, play dead, or detach a leg to distract predators.
Cellar Spiders (Pholcidae), as true spiders, possess venom glands and fangs. However, their venom is not potent enough to cause significant harm to humans. Research indicates cellar spider venom is relatively weak compared to other spiders.
The assertion that their fangs are too short to penetrate human skin is largely a myth. While small, their fangs can pierce human skin. A cellar spider bite typically results in minimal or no reaction, sometimes a mild irritation. Cellar spiders are not aggressive towards humans, and bites are rare, usually occurring only if provoked. They do not pose a medical threat to humans.
Why the Myth Endures
The persistent myth that “daddy long legs” are the most venomous spiders, yet harmless, stems from several factors. One reason is the imprecise use of the name, which applies to both non-venomous Harvestmen and mildly venomous Cellar Spiders. This ambiguity allows misconceptions about one group to be incorrectly attributed to the other. People often encounter both, leading to a conflation of their characteristics.
The myth may also stem from observations of cellar spiders preying on more dangerous spiders, like black widows. Their ability to subdue these arachnids led to the incorrect assumption that their own venom must be more potent. In reality, cellar spiders use their long legs and silk to entangle and immobilize prey from a safe distance, not relying solely on highly potent venom.
Exaggerated stories and urban legends contribute to the myth’s longevity, especially without clear information. The idea of a creature with deadly venom unable to harm humans creates a compelling, false narrative. Despite scientific evidence, the myth continues to circulate widely. Both Harvestmen and Cellar Spiders are largely harmless to humans and beneficial for controlling household pests.