Daddy longlegs are the most venomous spiders
The claim that daddy longlegs are the most venomous spiders but cannot bite through human skin is false on both counts. The term 'daddy longlegs' refers to at least three distinct creatures, only one of which is a true spider. Harvestmen (the most common referent) have no venom at all, and cellar spiders (true spiders) have weak venom with no medically significant effects on humans.
What we know
The daddy longlegs venom myth is complicated by the fact that 'daddy longlegs' is a common name applied to three entirely different animals in different parts of the world: harvestmen (Opiliones), crane flies (Tipulidae), and cellar spiders (Pholcidae).
Harvestmen are arachnids but not spiders. They have no venom glands, no fangs capable of injecting venom, and no silk glands. When disturbed, they may secrete a foul-smelling chemical to deter predators, but this is not venom. The Burke Museum of Natural History confirms they have no venom of any kind.
Crane flies are insects with no venom capability whatsoever.
Cellar spiders (Pholcidae) are true spiders and do have venom, like nearly all spiders. Arachnologist Rick Vetter at the University of California Riverside confirmed that pholcid venom is not the world's most potent spider venom. A 2019 study by arachnologist Charles Kristensen, referenced on the MythBusters episode on this topic, found that when pholcid venom was injected into mice, the effect was far weaker than black widow venom. Cellar spiders can bite humans, producing only a mild, short-lived reaction at most.
The 'fangs too small to bite' component of the myth is also inaccurate for cellar spiders: their fangs can penetrate human skin, they simply have no potent venom to inject.
Common claims
- Daddy longlegs are the most venomous spiders in the worldFalse - pholcid venom is weak
- Daddy longlegs cannot bite through human skinFalse - cellar spiders can bite humans
- Harvestmen are venomous spidersFalse - harvestmen have no venom and are not spiders