The question of whether a “daddy long legs” builds a web is complicated because the common name refers to three entirely different creatures. This linguistic overlap has created widespread confusion about the biology and behavior of these animals. Depending on where you are in the world, using this single name could refer to a true spider, a non-spider arachnid, or even an insect. To understand which of these creatures constructs silk traps, it is necessary to look past the shared nickname and focus on their scientific classifications.
The Non-Web Builder
The creature most often referred to as a “daddy long legs” that does not build a web is the harvestman, belonging to the Order Opiliones. Harvestmen are arachnids, meaning they are related to spiders, mites, and scorpions, but they are not classified as true spiders. Harvestmen lack the necessary silk glands (spinnerets) to produce webbing, meaning they are strictly ground-based foragers.
The harvestman is an opportunistic omnivore, primarily scavenging for decaying plant matter, fungi, or small, slow-moving invertebrates. It must actively hunt or scavenge, typically in cool, damp environments like leaf litter, under rocks, or in basements.
The Web-Building Spider
The animal that does build a web and is frequently called the “daddy long legs” is the cellar spider, which belongs to the Family Pholcidae. The cellar spider is a true spider (Order Araneae), possessing the distinct two-part body segmentation typical of all true spiders: a cephalothorax and an abdomen connected by a slender waist, or pedicel.
Cellar spiders construct a characteristic three-dimensional web that is often described as an irregular, messy, or tangled mesh. These webs are not sticky like those of orb-weavers, but instead rely on their intricate, haphazard structure to confuse and ensnare insects. Once prey is trapped in the tangled threads, the cellar spider quickly envelops the victim in a dense layer of silk before delivering a fatal bite.
The webs are commonly found in undisturbed, dark recesses like high ceiling corners, caves, attics, and cellars, which gives this arachnid its more formal common name. The long legs of the cellar spider are highly flexible and are used in a unique defensive behavior; when threatened, the spider rapidly vibrates or gyrates its body within the web, blurring its outline and making it difficult for a predator to target.
The Non-Arachnid Imposter
A third, completely unrelated creature also shares the popular nickname, which is the crane fly, belonging to the insect Order Diptera. Crane flies are true flies, evident by their six legs and a single pair of functional wings. As an insect, the crane fly is not an arachnid and therefore follows a different life cycle and set of behaviors.
Adult crane flies are slender, spindly-bodied flies that can reach up to 60 millimeters in length, adding to the visual confusion surrounding the “daddy long legs” name. They are short-lived and generally do not feed, focusing only on mating and egg-laying. They possess no mechanism for silk production and do not engage in web building.
Visual Identification Differences
Distinguishing between the web-building cellar spider and the non-web-building harvestman can be easily achieved by observing a few simple physical traits. The most immediate difference lies in the body structure: the cellar spider has two clear body segments separated by a narrow constriction, whereas the harvestman appears to have one fused, oval-shaped body. If the creature is stationary in a messy, permanent web, it is certainly the cellar spider.
Another reliable distinction is the number of eyes; most harvestmen possess only two eyes, which are positioned on a small turret-like mound on the top of the body. In contrast, the cellar spider typically has eight eyes, although some species have six, arranged in groups on the front of the cephalothorax. Harvestmen are also more commonly found wandering on the ground or on outdoor vegetation, while cellar spiders are almost always found hanging inverted in their messy webs in high corners of indoor spaces.