The common name “daddy long legs” causes widespread confusion because it is applied to three distinctly different creatures across the world, making a simple “yes” or “no” answer impossible without specifying the organism. The identity of the animal often depends on geographic location and whether the creature is found indoors, outdoors, or flying. This ambiguity stems from the shared characteristic of having exceptionally long, thin legs. Resolving the question of whether a daddy long legs is a spider requires examining the specific biological order of the animal being discussed: a true spider, a non-spider arachnid, or a flying insect.
The True Spider
In many parts of the world, particularly within homes, the name refers to the Cellar Spider, a fragile arachnid belonging to the order Araneae and the family Pholcidae. These organisms possess the definitive characteristics of a true spider. Like all spiders, the cellar spider’s body is divided into two distinct segments: the cephalothorax (fused head and thorax) and the abdomen, joined by a narrow pedicel or “waist”. The cellar spider uses its fangs, or chelicerae, to inject venom into its prey and constructs a messy, irregular web of silk threads, often found in dark, damp corners. When threatened, the spider rapidly vibrates its web and body, blurring its outline and making it difficult for predators to target.
The Arachnid That Isn’t a Spider
In North America, the creature most commonly called a daddy long legs is the Harvestman, an animal belonging to the order Opiliones. Harvestmen are arachnids, placing them in the same class as spiders, but they are not true spiders.
Anatomy and Defense
The most significant anatomical difference is that the harvestman’s body appears as a single, fused oval segment, with the cephalothorax and abdomen broadly joined and lacking a constriction. Unlike spiders, harvestmen completely lack silk glands and do not spin webs to catch prey. Harvestmen have pincer-like jaws for grasping food and will sometimes shed a leg as a distraction when escaping a predator, a defense mechanism known as autotomy.
Diet and Venom
They are omnivorous scavengers and predators that actively hunt small insects, feed on decaying plant matter, or scavenge bird droppings. They do not possess venom glands, which dispels the myth that the daddy long legs is the world’s most venomous spider.
The Insect Imposter
The third creature sometimes referred to as a daddy long legs is the Crane Fly, a flying insect belonging to the order Diptera (true flies). This animal is not an arachnid at all. As an insect, its body is divided into three distinct sections—head, thorax, and abdomen—and it possesses only six legs. The Crane Fly has a single pair of functional wings, with the hind wings reduced to small, club-shaped balancing organs called halteres. The adult flies are harmless, often feeding on nectar or not feeding at all during their short lifespan, and their resemblance to a giant mosquito is the sole reason for their confusing common name.