The name “daddy long legs” is a common term used across different regions to describe several distinct arthropods, leading to widespread confusion about their identity and purpose. These creatures share the characteristic of having long, thin legs relative to their small bodies, but they belong to entirely separate biological orders. This article clarifies the true identities of these inhabitants and explains the diverse ecological roles they play in nature.
Resolving the Identity Crisis
The familiar term “daddy long legs” most commonly refers to three separate groups: Harvestmen, Cellar Spiders, and Crane Flies. Harvestmen (order Opiliones) are arachnids but are not true spiders. Unlike true spiders, a Harvestman’s cephalothorax and abdomen are broadly joined, making the body appear as a single, oval structure. They possess only two eyes, not the typical eight seen in most spiders, and they lack the silk glands necessary to spin webs.
Cellar Spiders (family Pholcidae) are true spiders, recognizable by their two separate body segments and eight eyes. They construct large, messy, tangled webs, often in dark areas like basements and cellars. When disturbed, they vibrate rapidly in their webs to confuse potential threats, earning them the nickname “vibrating spiders”.
The third creature, the Crane Fly, is not an arachnid but an insect belonging to the order Diptera (true flies). Crane Flies are easily distinguished by their wings and six legs, separating them completely from the eight-legged Harvestmen and Cellar Spiders. The only commonality among the three is their lengthy, delicate leg structure.
Ecological Roles and Feeding Habits
The three creatures known by the same common name have specialized and beneficial functions in their ecosystems, primarily defined by their diets. Harvestmen are notable for their omnivorous and scavenging habits, a trait unusual among arachnids, which are typically strict predators. Their diet consists of a wide variety of materials, including decaying plant matter, fungi, bird droppings, and small dead insects.
Harvestmen also actively hunt soft-bodied insects but do not use venom to subdue their prey. Instead, they use specialized mouthparts called chelicerae to grasp and tear food apart. Their role as detritivores makes them beneficial members of the clean-up crew in gardens and forests, helping to recycle organic material.
Cellar Spiders are active predators that use their webs to capture various arthropods, including many common household pests. They control populations of flying insects like gnats and mosquitoes, which become ensnared in their irregular webs. They are also known to hunt and consume other, sometimes larger, spiders, such as the Black Widow, by casting silk over them from a distance. This predatory behavior extends to kleptoparasitism, where they invade the webs of other spiders to steal caught prey.
Addressing the Safety Myths
A persistent urban legend claims that the “daddy long legs” has the world’s most toxic venom but is rendered harmless because its fangs are too small to penetrate human skin. This statement is inaccurate, depending on which of the three creatures is being discussed. The Harvestman, the creature most often referred to by the name, does not produce venom at all, possessing neither fangs nor venom glands.
Crane Flies are equally harmless to humans, as they are non-venomous insects whose adult mouthparts are not designed to pierce skin. The Cellar Spider, the only true spider of the group, does produce venom like nearly all spiders. However, the venom of the Cellar Spider is extremely mild and poses no medical threat to humans.
While it is possible for a Cellar Spider to bite, their fangs are relatively small and weak, and there is no evidence of their venom causing a detrimental reaction in people. The myth likely arose from the Cellar Spider’s ability to kill dangerous spiders, leading to the false conclusion that their venom must be highly potent. All three types of “daddy long legs” are overwhelmingly beneficial or neutral to human interests.