The common name “daddy longlegs” is widely used, yet it refers not to a single creature, but to three distinct types of arthropods. This confusion causes persistent questions regarding whether these animals can bite humans. The answer depends entirely on which of the three long-legged organisms is being observed. Understanding the biological differences between these three groups separates the scientific facts from the popular myths.
The Identity Crisis: Clarifying “Daddy Longlegs”
The first and most widespread creature called “daddy longlegs” is the Harvestman (order Opiliones). Harvestmen are arachnids related to spiders, but they are not true spiders because their body is fused into a single, oval segment, unlike the distinct two-part body of a spider. They have a single pair of eyes, often located on an elevated mound. Crucially, they lack the silk-producing glands and venom that define true spiders.
The second group is the Cellar Spider (Pholcidae), a true spider commonly found in basements and dark corners. Cellar spiders possess typical spider anatomy, featuring two distinct body segments and fangs (chelicerae) used to subdue prey. They are known for their extremely long, thin legs relative to their small body size and for constructing large, messy, irregular webs.
The third creature is the Crane Fly (family Tipulidae). Unlike the others, the crane fly is a true insect, distinguishable by its three body segments and two wings. Often mistaken for a giant mosquito due to its size and delicate, elongated legs, the crane fly is completely harmless. Its inclusion in the “daddy longlegs” group is based purely on its physical appearance.
Do They Bite? Separating Fact from Myth
The question of biting capacity yields a different answer for each creature. The Crane Fly cannot bite or sting humans, as its adult mouthparts are not designed for piercing skin; they are either used for consuming nectar or are non-functional. For the Harvestman, the answer is also a definitive no. These organisms possess no fangs and no venom glands. Their chelicerae are modified for chewing and tearing solid food, making them incapable of penetrating human skin.
Cellar Spiders technically can bite, as they are equipped with fangs and venom glands, but the act is extremely rare. A popular myth claims the cellar spider possesses the world’s most potent venom, but that its fangs are too short to break human skin. This claim is untrue. The venom produced by cellar spiders is relatively mild and not considered medically significant to humans, even if a bite occurs.
While venomous to their prey, the cellar spider’s venom poses no danger to people. There is no scientific documentation of a cellar spider bite causing any serious reaction in a human. The myth likely gained traction because cellar spiders prey on more dangerous species, such as the Redback spider in Australia, leading to the incorrect assumption of highly potent venom.
Understanding Their Anatomy and Behavior
The physical characteristics and behaviors of the arachnids further explain why they pose no threat to humans. The Cellar Spider’s chelicerae (jaws) are quite small. While they can technically pierce very thin skin, they lack the strong musculature needed to consistently puncture a person’s thicker epidermis. They are not aggressive hunters, but passive trappers that rely on their irregular webs to catch prey.
When threatened, the Cellar Spider’s primary defense is not biting, but rapidly vibrating its web, making it appear as a blurred shape to a potential predator. Harvestmen also employ non-biting defensive tactics. These include shedding a leg to distract an attacker or releasing a foul-smelling chemical secretion from specialized glands. This noxious odor serves as a deterrent against animals that might try to eat them.
All three creatures—Harvestmen, Cellar Spiders, and Crane Flies—are generally timid and non-aggressive toward humans. Their primary focus is on feeding, scavenging, or reproduction. Any physical interaction with a person is almost always an accidental defensive reaction. The absence of medically significant venom, coupled with specialized mouthparts and behavioral defenses, ensures they remain harmless occupants of homes and gardens.