A longstanding urban legend holds that daddy long legs spiders are poisonous, but they are not dangerous to humans because their fangs are too short to penetrate human skin.
It’s a myth.
What are Daddy Long Legs?
“Daddy Long Legs” is a term used by different people in diverse locales to describe a variety of creatures. It could refer to creatures in the Order Opiliones (also known as harvestmen). Another creature known as daddy long legs is the spider in the family Pholcidae, previously known as cellar spiders. In some areas, crane flies are also called daddy long legs.
Regarding the part of the rumor that daddy long legs have small fangs and therefore cannot penetrate human skin, University of California Riverside entomologists point out that other spiders, such as the brown recluse, have similarly small fangs, and have no problem imparting venom to their human victims.
Are they Poisonous?
According to a webpage devoted to Opiliones on the Orkin website, harvestmen do not make venom, and thus cannot be poisonous. Below is a quote from the page:
Unlike spiders, harvestmen aren’t venomous and don’t create silk webs. Unlike spiders that produce venom and deliver the venom via fangs, harvestmen don’t make venom and can’t deliver venom through a bite. This debunks an urban legend that falsely states daddy longlegs are the most poisonous spiders in the world, but their fangs are too small to penetrate human skin. In fact, harvestmen mouthparts, which they use to hold prey while eating them, are similar to crabs.
In addition, a 2004 episode of Mythbusters (episode 13) attempted to prove or disprove the daddy long legs legend. Host Adam Savage was able to prompt a bite, and reported nothing more than a subtle burning sensation that lasted only a few seconds. Results of the episode can be seen on a webpage at discovery.com as well as on a page from mythbusterresults.com.
There have been no studies regarding the toxicity of the venom of pholcids.
In 2015 Burke Museum posted a page regarding the Daddy Long Legs myth. Its brief discussion of the urban legend states:
Three different unrelated groups are called “daddy-longlegs.” Harvestmen have no venom of any kind. None at all! Same with crane flies . Pholcid spiders have venom (like almost all spiders) but there’s nothing special about it; in fact, a recent study showed that pholcid venom is unusually weak in its effect on insects.
The same month that Burke Museum posted its page on the myth, a similar article appeared on the Australian Museum website. Their take on the myth writes:
There is a persistent belief that the Daddy-long-legs Spider has the most toxic venom of all spiders. However, there is no scientific evidence to back this up. The myth probably grew from observations that the Daddy-long-legs Spider will kill and eat a Redback Spider. However, the venom is not actually that potent, even for insects.
Google Trends History
The Google Trends graph below shows search interest in “daddy long legs poisonous” going back to 2005. Interest seems to have gradually increased, and appears to surge every year around August and September. Curiosity may surge in these months because this is when daddy long legs are most commonly seen.
The rumor that daddy long legs spiders are poisonous is nothing more than a pervasive urban legend.
Updated March 6, 2016
Originally published October 2013