The common name “daddy long legs” is a source of widespread confusion because it refers to at least two distinct types of arthropods, and sometimes even a third—the crane fly. This ambiguous naming convention has led to many myths about whether these creatures are harmless or beneficial to have in your home and garden. To assess their value, it is necessary to correctly identify which long-legged creature is being discussed and understand its specific ecological role.
Defining the Two Arthropods
The two primary creatures called “daddy long legs” are the Harvestman (Order Opiliones) and the Cellar Spider (Pholcus phalangioides). Although both are eight-legged arachnids, they belong to entirely different scientific orders and possess distinct physical characteristics. Harvestmen are not true spiders; their body segments are broadly fused, giving the appearance of a single, oval-shaped body, and they possess only one pair of eyes on a raised turret called an ocularium.
Cellar Spiders, by contrast, are true spiders (Order Araneae) whose bodies clearly show two distinct segments: a cephalothorax and an abdomen connected by a thin waist. Unlike Harvestmen, Cellar Spiders spin messy, irregular webs to capture prey and typically have eight eyes arranged in groups. A simple way to distinguish them is to look for a web; if the creature is hanging upside down in a messy web, it is a Cellar Spider, but if it is wandering freely, it is likely a Harvestman.
The Beneficial Role of Harvestmen
The Harvestman (Opiliones) is a generalist scavenger and omnivore in outdoor environments. Unlike true spiders, Harvestmen do not possess silk glands or venom, relying on chewing mouthparts to consume solid food. This feeding strategy makes them important decomposers in garden and forest ecosystems.
Their diet is varied, consisting of decaying plant matter, fungi, bird droppings, and small dead invertebrates. They also actively prey on soft-bodied garden pests like aphids, springtails, and small caterpillars, as well as insect eggs. By consuming this wide range of material, Harvestmen aid in natural pest control and nutrient recycling.
Cellar Spiders as Indoor Pest Control
Cellar Spiders (Pholcus phalangioides) are commonly found indoors, residing in quiet, sheltered areas like basements, cellars, and garages. They are effective biological controllers of nuisance arthropods within the home environment. They spin loose, irregular, three-dimensional webs, often found in the corners of rooms, where they wait for prey.
The primary benefit of Cellar Spiders is their predatory behavior toward other spiders, including less desirable house guests. They actively venture out of their webs to hunt and kill other spiders, even larger species such as house spiders and wolf spiders. They have been observed preying on medically significant species, which likely fueled the myth that the Cellar Spider possesses the world’s most potent venom.
Are They Dangerous
The widespread fear that “daddy long legs” are deadly is a persistent myth that lacks scientific basis and confuses the two different creatures. Harvestmen (Opiliones) are completely harmless to humans because they do not possess venom glands or fangs. They rely on chewing mouthparts that are too small and weak to penetrate human skin, even if they attempted to bite.
Cellar Spiders, being true spiders, do possess venom, but it is not medically significant to humans. While they are capable of biting, their venom is weak and primarily effective against insect and spider prey. A bite to a human is extremely rare, usually resulting in a mild, short-lived stinging sensation with no long-term consequences, debunking the myth of the “most venomous spider.”