The question of whether a daddy long legs can kill a human is a common fear, often perpetuated by an enduring urban myth. The immediate answer is a definitive no; none of the creatures known by this name pose any serious threat to people. This widespread confusion and the resulting fear stem from the fact that the informal name “daddy long legs” is used to describe three completely different types of arthropods across various regions. To understand the harmless nature of these animals, it is necessary to differentiate between the true spider, the non-venomous arachnid, and the insect that share this moniker.
Identifying the Real “Daddy Long Legs”
The ambiguity of the name complicates any discussion about danger, as three distinct groups are involved. The Cellar Spider (Pholcidae) is a true spider and possesses venom. These are the spiders most commonly found hanging in webs in the quiet, dusty corners of basements and cellars. They are recognizable by their small, oval-shaped bodies and extremely long, thin legs.
Another creature widely called the daddy long legs is the Harvestman (Opiliones). While they are arachnids, they are not true spiders. Finally, the Crane Fly (Tipulidae) is a large, mosquito-like insect that looks clumsy as it flits around lights. These three organisms are only linked by their common name and their disproportionately long, slender legs.
The Truth About the Cellar Spider’s Venom
The Cellar Spider (Pholcidae) is the only one of the three creatures that is venomous, but the myth surrounding its toxicity is greatly exaggerated. The popular story suggests their venom is deadly but their fangs are too small to pierce human skin, which is scientifically inaccurate. Cellar spiders possess a mild venom that is highly effective for quickly subduing their prey, which typically consists of small insects and even other spiders.
Scientific studies have indicated that the venom’s efficacy against mammals is extremely low. This weak venom is primarily a tool for incapacitating invertebrate prey, posing no medical danger to humans.
The physical capability of the spider to bite is another point of confusion. Cellar spiders have fangs, or chelicerae, which are quite small, measuring around a quarter of a millimeter. While they are usually too delicate to fully penetrate the thicker layers of human skin, a bite is possible in areas where the skin is thinner or if the spider is severely provoked. If a bite does occur, the symptoms are typically limited to a minor, localized stinging sensation or a slight, temporary redness. The minimal reaction confirms that the spider’s venom poses no threat to human health.
Harmless Look-Alikes: Harvestmen and Crane Flies
The other two creatures that share the common name are entirely harmless and present no risk whatsoever. Harvestmen (Opiliones) are often mistaken for spiders, but they are easily differentiated because their body segments are fused together, giving them a single, oval appearance. Crucially, they lack venom glands, meaning they are physically incapable of producing or injecting venom.
Harvestmen also do not possess the hollow fangs necessary for envenomation. Instead, they have small, grasping mouthparts used to tear apart their food, which consists of dead organic material and small, soft-bodied prey. Similarly, the Crane Fly (Tipulidae) is a simple insect, not an arachnid, and is incapable of biting or stinging. Adult crane flies often have non-functional mouthparts, or they only use them to drink water, and their only purpose is reproduction.