The term “daddy long legs” commonly refers to three distinct creatures: cellar spiders, harvestmen, and crane flies. This widespread use has led to many myths, especially regarding their ability to bite and venom potency. Understanding their biological differences clarifies these misconceptions and provides accurate information about their characteristics and interactions with humans.
Common “Daddy Long Legs” Species
Cellar spiders (Pholcus phalangioides) are one creature commonly called “daddy long legs”. These true spiders belong to the family Pholcidae. They are recognized by their pale yellow-brown, almost translucent bodies and exceptionally long, thin legs, often found in basements, corners of rooms, and other undisturbed, low-light areas where they build loose, irregular webs.
Harvestmen (order Opiliones) are another animal sharing the “daddy long legs” moniker. They are arachnids, like spiders, but are not true spiders. A key distinguishing feature is their single, oval-shaped body segment where the cephalothorax and abdomen are broadly joined, unlike spiders which have two distinct body parts. Harvestmen typically have two eyes, whereas most spiders possess eight.
The third creature is the crane fly (family Tipulidae), an insect. These flies resemble large mosquitoes with their long, slender legs, bodies, and a single pair of clear wings. Crane flies are distinct from both spiders and harvestmen, as they are insects with six legs.
Biting Abilities and Behavior
Cellar spiders (Pholcus phalangioides) are true spiders and can bite. Their fangs are very small, measuring approximately a quarter of a millimeter. While they can technically penetrate human skin, bites are rare and typically occur only if the spider feels threatened. Cellar spiders are non-aggressive and prefer to vibrate rapidly in their webs or flee when disturbed.
Harvestmen (Opiliones) cannot bite humans. Despite having mouthparts called chelicerae, these are designed for chewing and tearing food, not for piercing skin or injecting venom. Their mouthparts are very small and not strong enough to break human skin. Harvestmen are scavengers or predators of small insects and decaying matter, using their chelicerae to process food.
Crane flies (Tipulidae) also cannot bite humans. As adult flies, many species do not have functional mouthparts for feeding, or if they do, they are adapted for consuming nectar.
The Truth About Their Venom
Cellar spiders, like nearly all true spiders, possess venom. However, the common urban legend that they have the world’s most potent venom but fangs too short to bite humans is a myth. Their venom is not medically significant or harmful to humans; any bite would likely result in a mild, temporary effect similar to a minor sting. Research indicates cellar spider venom is quite weak compared to other spiders.
Harvestmen are not venomous. They do not have venom glands, a key distinction from true spiders. The myth of them being highly venomous but unable to bite is false. Instead, some harvestmen species possess defensive scent glands that secrete a peculiar-smelling fluid when disturbed.
Crane flies are also not venomous. They do not produce venom and pose no threat.