Whether daddy long legs eat spiders depends entirely on which creature you mean, because the nickname “daddy long legs” is shared by three very different animals. One of them is a dedicated spider predator that regularly invades webs and kills the residents. Another is a ground-dwelling scavenger that eats mostly dead things, fungi, and plant matter. The third is a flying insect that barely eats at all as an adult. The complexity is real, but it starts with a naming problem.
Three Animals, One Nickname
The confusion around this question exists because “daddy long legs” is not a single species or even a single type of creature. In different parts of the English-speaking world, the name gets applied to cellar spiders, harvestmen, and crane flies. These three are not closely related, do not share the same body plan, and lead completely different lives. The only thing they have in common is long, spindly legs.
Cellar spiders belong to the family Pholcidae. They are true spiders with two body segments, silk glands, venom, and fangs. You find them in basements, garages, and room corners, hanging upside down in loose, messy webs. Harvestmen belong to the order Opiliones. They are arachnids like spiders, but their body is fused into a single oval lump, and they have no venom, no silk, and no fangs. They wander along the ground and over vegetation, often in damp, shaded spots. Crane flies are insects in the family Tipulidae. They look like oversized mosquitoes, have wings, six legs, and no connection to the arachnid world at all.
When someone asks “do daddy long legs eat spiders,” they usually mean cellar spiders, since these are the ones people see in and around spider webs. But since harvestmen and crane flies carry the same name, the question deserves a full accounting for all three.
Cellar Spiders Are Genuine Spider Predators
Cellar spiders are the one “daddy long legs” that really does eat other spiders, and they do it regularly. Pholcids are well known for a hunting strategy sometimes called araneophagic behavior, which simply means preying on other spiders. They accomplish this through a combination of web invasion and specialized attack techniques that give them an edge against species you might expect to be tougher.
Research on the genus Pholcus illustrates how this plays out in practice. In laboratory contests between two species of cellar spider, researchers found that the smaller invading species, Pholcus manueli, could successfully take over the webs of its larger relative Pholcus phalangioides when conditions favored the invader. Well-fed invaders were more aggressive and more likely to claim the web, while food-limited invaders tended to avoid confrontation, sometimes allowing the two species to share space rather than fighting.1Biological Invasions. Contests between web spiders: patience as a strategy for successful invasion The body size difference between contestants mattered most in determining who won, but nutritional state influenced how willing each spider was to escalate.
These contests between pholcid species are just one window into a broader pattern. Cellar spiders also invade the webs of unrelated spider species, including house spiders and black widows. They enter the web quietly, vibrate the silk to mimic trapped prey or a potential mate, and when the resident spider approaches to investigate, the cellar spider wraps it in silk from a distance, using its long legs to keep its body out of striking range. This long-range silk-throwing technique is key to how a seemingly fragile cellar spider can overpower stockier, more heavily armed species.
The Whirling Trick
When cellar spiders themselves face danger, they have a distinctive defensive behavior that anyone who has poked at a cellar spider web has probably witnessed. If disturbed, the spider stays on its web but begins swinging its body in rapid circles, blurring itself into a spinning haze. Its legs stay anchored to the silk while the body whips around at high speed.2Journal of Zoology. Anti‐predator defences of Pholcus phalangioides (Araneae, Pholcidae), a web‐building and web‐invading spider This whirling makes the spider much harder for a predator to grab and also causes the web to vibrate unpredictably, which may confuse other spiders that rely on web vibrations to locate prey.
The whirling behavior is relevant to the spider-eating question because it works both as defense and as part of the cellar spider’s aggressive lifestyle. A spider that lives by invading other spiders’ webs needs some way to protect itself when the resident fights back. The combination of long-range silk attacks and the ability to become a difficult-to-grab blur gives cellar spiders an unusual toolkit that few other spiders can match.
What Cellar Spider Venom Actually Does
There is a popular myth that daddy long legs possess the most potent venom of any spider but have fangs too small to penetrate human skin. This is false on both counts, but the real story about cellar spider venom is more interesting than the myth.
Cellar spiders do have venom, and it is not trivial. A proteomic study of the pholcid species Physocyclus mexicanus found that roughly half the venom’s composition consists of proteins matching known venom toxins, including metalloprotease enzymes and peptide neurotoxins. Researchers identified 17 new groups of venom peptides in this species alone. When tested on crickets, the crude venom produced paralysis at doses comparable to those seen in other spider venoms.3PubMed Central. Not so Dangerous After All? Venom Composition and Potency of the Pholcid (Daddy Long-Leg) Spider Physocyclus mexicanus The crickets showed a distinctive flaccid paralysis with visible darkening in some body regions, suggesting a venom that works differently from that of many other spider families.
As for the “fangs too small” claim, pholcid fangs can and do pierce human skin on the rare occasions when a cellar spider bites a person. The bite is typically mild, producing a brief burning sensation at most. Cellar spider venom is effective enough to subdue insects and other spiders, which is what it evolved to do. It is not medically significant to humans, not because the fangs cannot deliver it, but because the venom simply is not very dangerous to something our size. The myth likely persists because people see cellar spiders killing much larger spiders and assume the venom must be extraordinarily potent, when in reality the cellar spider’s success comes more from its silk-based hunting strategy than from especially powerful toxins.
What Harvestmen Actually Eat
Harvestmen, the round-bodied, long-legged arachnids that wander across forest floors and garden walls, have a completely different relationship with food. They are not hunters in any specialized sense. They are generalist foragers that eat whatever they happen to find, and their diet is remarkably broad.
A study of the harvestman Leiobunum formosum used laboratory feeding trials, electron microscopy of fecal pellets, and chemical analysis to piece together what these animals consume in the wild. The results showed a diet that included plant material, fungi, fragments of arthropods, and even bristles from earthworms. Stable isotope analysis confirmed that individual harvestmen varied considerably in what they ate, consistent with opportunistic scavenging rather than any targeted hunting strategy.4Arachnology. Diet of the harvestman Leiobunum formosum (Opiliones, Sclerosomatidae)
Could a harvestman eat a spider? In theory, if it encountered a dead or dying spider, it might scavenge the remains. Harvestmen have been observed feeding on dead arthropods of various kinds. But actively hunting and killing a living spider is not something harvestmen are equipped for. They lack venom, lack silk for restraining prey, and lack the predatory behavior patterns that make cellar spiders effective spider-killers. When people see a harvestman near a spider web, the harvestman is far more likely to be passing through or scavenging a discarded carcass than attacking the web’s resident.
Harvestmen Spend More Time Avoiding Being Eaten
If anything, harvestmen are more likely to be prey than predator in encounters with spiders. These soft-bodied animals have evolved an impressive suite of defensive strategies precisely because they are vulnerable to a wide range of predators, including spiders, birds, and small mammals.
Harvestmen defenses include chemical secretions from specialized glands, the ability to shed a leg when grabbed (the detached leg keeps twitching, distracting the predator), aggregation in large groups, freezing in place, bobbing their body rapidly up and down, vibrating, and even producing sounds.5BioOne Complete. Staying alive: how harvesters avoid predation The leg-shedding trick, called autotomy, is the one most people have experienced firsthand. If you have ever tried to pick up a harvestman only to have it leave a still-wiggling leg in your fingers while the rest of it scurries away, you have watched one of these defenses in action.
The sheer variety of anti-predator strategies tells you something about where harvestmen sit in the food web. Animals that invest this heavily in not being eaten are not apex predators in their micro-ecosystem. They are prey items that have found a range of ways to survive long enough to reproduce.
Crane Flies Have Almost Nothing to Do with This Question
Crane flies, the gangly, moth-like insects that blunder into your house in late summer and bounce off lampshades, are the third creature called “daddy long legs” in some regions, particularly in the United Kingdom and parts of the Commonwealth. Their inclusion in this conversation is almost a punchline, because adult crane flies eat very little at all. Most species either do not feed as adults or consume only small amounts of nectar or water. Their adult lives are short and devoted almost entirely to mating and egg-laying.
Crane fly larvae, which live in soil and are sometimes called leatherjackets, feed on decaying organic matter and plant roots. At no stage of their life cycle do crane flies have any interaction with spiders as either predator or prey in any meaningful ecological sense. If you are asking whether daddy long legs eat spiders and you mean crane flies, the answer is simply no, with no qualifications needed.
Why Cellar Spiders Are So Good at Killing Other Spiders
Returning to the one “daddy long legs” that really does eat spiders, it is worth thinking about what makes cellar spiders such effective araneophages. Several features work together. Their long legs allow them to attack from a distance that keeps their body out of the strike zone of their prey’s fangs. Their silk is used offensively, thrown at the target spider in rapid wrapping motions, rather than serving only as a passive web. Their webs are structurally simple, which means they can build a new one quickly if they move into a new space or need to repair damage from a fight.
Cellar spiders are also patient. In the web-invasion contests between Pholcus species, many encounters ended without a decisive winner because the invading spider chose not to escalate.1Biological Invasions. Contests between web spiders: patience as a strategy for successful invasion This patience appears to be a viable strategy in itself. An invader that enters a web, assesses the situation, and retreats when outmatched can try again later or try a different web. Over time, this cautious approach allows smaller cellar spider species to gradually displace larger ones from shared habitats, turning what looks like a disadvantage in any single encounter into a long-term competitive edge.
The combination of distance-attack capability, disposable webs, and willingness to pick battles carefully helps explain something that puzzles a lot of people who see cellar spiders in their homes. These delicate-looking spiders, with their tiny bodies and impossibly thin legs, seem like they should be easy prey for the bigger, more robust spiders they share space with. But the cellar spider’s strategy is specifically adapted for spider-on-spider combat in a way that raw size does not predict.
What You Are Probably Seeing in Your House
If you have noticed a cellar spider hanging near or within the remains of another spider, you are looking at a real predation event. Cellar spiders frequently kill and consume house spiders, cobweb spiders, and other web-builders that share indoor habitats. The messy webs that accumulate in ceiling corners are often cellar spider webs layered over the remains of previous meals, including the drained husks of other spiders.
Some people deliberately tolerate cellar spiders indoors because of this predatory behavior, viewing them as a form of passive pest control. A cellar spider population in your basement can reduce the numbers of other spider species over time. Whether that tradeoff appeals to you depends on how you feel about trading one kind of spider for another. The cellar spiders themselves are not aggressive toward humans, rarely bite even when handled, and produce no medically significant effects when they do.
Harvestmen, by contrast, are outdoor animals that sometimes wander inside but do not establish indoor populations the way cellar spiders do. If you find a harvestman in your house, it almost certainly walked in by accident and would prefer to be back outside among leaf litter and damp soil, where its preferred foods of fungi, decaying matter, and the occasional small invertebrate are available.
The Venom Myth and Where It Came From
The “most venomous spider in the world” myth deserves a closer look because it illustrates how the three-creature naming confusion compounds misinformation. The myth usually goes something like this: daddy long legs have the most powerful venom of any spider, but their mouths are too small to bite a human, so they are harmless. Every piece of this is wrong, but the wrongness depends on which animal you are talking about.
Harvestmen have no venom at all. They are not spiders, and they do not have venom glands or fangs. The claim is meaningless when applied to them. Crane flies also have no venom and are not even arachnids. The claim can only even be evaluated for cellar spiders, and as the venom research shows, pholcid venom is functional but unremarkable by spider standards, producing paralysis in crickets at doses comparable to those of other small spider species.3PubMed Central. Not so Dangerous After All? Venom Composition and Potency of the Pholcid (Daddy Long-Leg) Spider Physocyclus mexicanus It is certainly not the most potent spider venom known. And cellar spider fangs, while small, are capable of piercing human skin. The whole myth collapses under any scrutiny, but it persists because people watch cellar spiders defeat larger spiders and reach for a dramatic explanation.
The reality is less cinematic but more elegant. Cellar spiders beat bigger spiders not because they possess some extraordinarily lethal toxin, but because their entire predatory strategy, from the long-legged silk-throwing to the web invasion tactics to the patience in picking fights, is fine-tuned for exactly this kind of combat. It is a behavioral advantage, not a chemical one.
Harvestmen Aggregations and Their Strange Social Lives
One behavior of harvestmen that has fascinated both researchers and casual observers is their tendency to form dense clusters, sometimes involving hundreds or even thousands of individuals packed tightly together on a tree trunk, rock face, or building wall. These aggregations are primarily a defensive strategy, making it harder for a predator to single out one individual and creating a combined chemical deterrent from the group’s defensive secretions.5BioOne Complete. Staying alive: how harvesters avoid predation
If you have ever stumbled across a mass of harvestmen clumped together, the sight can be unsettling in a way that reinforces their undeserved scary reputation. But these aggregations are basically the opposite of predatory behavior. They are the response of an animal that has no venom, no silk, and no way to fight back against most attackers, gathering in numbers because individual defense is not enough. The chemical secretions produced by harvestmen glands can smell distinctly unpleasant and are sometimes enough to deter a bird or lizard. At scale, a cluster of hundreds of harvestmen producing these secretions simultaneously creates a more effective deterrent than any individual could manage alone.
These clusters also serve thermoregulatory and moisture-retention purposes. Harvestmen are sensitive to drying out, and huddling together reduces water loss. The groups tend to form in cool, humid microhabitats, which is why you find them under bridges, in cave entrances, and on the shaded sides of trees. None of this has anything to do with hunting spiders, but it is a big part of what makes harvestmen successful as a group despite being individually vulnerable.