The claim is the Daddy Long Legs (Pholcus phalangioides) spider is the most venomous spider in the world, but that its fangs are too small to be able to penetrate human skin.

The wikipedia article calls it an urban myth and links through to some supposed "research", but its just some guy claiming:

There is no scientific basis for the supposition that they are deadly poisonous and there is no reason to assume that it is true.

Which I don't feel a lack of evidence should stand as claimed scientific research.

There is also a link to a myth busters episode where they apparently get a Daddy Long Legs spider to bite someone.

Is it possible for the Pholcidae spiders fangs to penetrate the skin and has there been any official measurement into the common dose size and toxicity of the venom?

  • 10
    Maybe in 100,000 years when it will be evolution's response to children constantly pulling their legs off.
    – LarsTech
    Jul 22, 2011 at 14:18
  • 1
    I had always heard this as a child as well. Jul 22, 2011 at 22:36
  • What we in the UK call a daddy long-legs isn't a spider at all, but an insect. And it's not poisonous. Jul 28, 2011 at 10:17
  • @LarsTech - yes, but then the response of evolution might be to add poisonous spines to the legs.
    – user3344
    Sep 17, 2013 at 13:57
  • Depends on whether "lack of evidence" means it wasn't looked into, or whether it was examined and there was nothing to support the positive case. Apr 14, 2020 at 15:48

2 Answers 2


It's a myth.

From the University of California, Riverside:

... There is no scientific basis for the supposition that they are deadly poisonous and there is no reason to assume that it is true.

There is no reference to any pholcid spider biting a human and causing any detrimental reaction.

If these spiders were indeed deadly poisonous but couldn't bite humans, then the only way we would know that they are poisonous is by milking them and injecting the venom into humans.
For a variety of reasons including Amnesty International and a humanitarian code of ethics, this research has never been done.

Furthermore, there are no toxicological studies testing the lethality of pholcid venom on any mammalian system (this is usually done with mice). Therefore, no information is available on the likely toxic effects of their venom in humans, so the part of the myth about their being especially poisonous is just that: a myth.

What about their fangs being too short to penetrate human skin?

Pholcids do indeed have short fangs, which in arachnological terms is called "uncate" because they have a secondary tooth which meets the fang like the way the two grabbing parts of a pair of tongs come together.

Brown recluse spiders similarly have uncate fang structure and they obviously are able to bite humans.

There may be a difference in the musculature that houses the fang such that recluses have stronger muscles for penetration because they are hunting spiders needing to subdue prey whereas pholcid spiders are able to wrap their prey and don't need as strong a musculature.

So, again, the myth states as fact something about which there is no scientific basis.

A video of the MythBusters can be watched here:

Supposedly, daddy longlegs possess extremely powerful poison, but their fangs are too short to penetrate human skin.

To find out, Jamie and Adam hunted down a host of daddy longlegs and took them to a spider specialist who could milk out their venom.

Next, the spider specialist compared the toxicity of daddy longlegs venom to black widow venom (on mice). The red-bellied widow won out, busting the myth.

A microscopic measurement of the long-legged spider's fangs proved their miniscule quarter-millimeter length could puncture human skin, taking a double bite out of the daddy longlegs myth. [Source]

As seen in the video Adam did let himself get bitten and only felt "a tiny little burning ".

  • 8
    one of the better (scientifically speaking) Mythbusters episodes :)
    – jwenting
    Jul 22, 2011 at 13:15
  • 5
    @jwenting: Indeed, the didn't even blew up the spider afterwards! Jul 23, 2011 at 10:37

This is from the Straight Dope:

Herman Vanuytven came forth from the Arachnology Home page (http://www.ufsia.ac.be/Arachnology/Arachnology.html). Herman's response:

"The problem with the 'Daddy Longlegs' is that the name is used for several kinds of animals, 2 of them arachnids:

1) The family Phalangiidae (a part of the opilionids [harvestmen], a different order than spiders)

2) a spider: Pholcus phalangioides

Number one doesn't have poison glands. Number two has poison glands but as far as is known in the scientific world, nobody has ever been bitten by one of them. It's not sure if the poison has ever been investigated since there was no need for it."

So, in short, this has never been investigated, and it hasn't been determined whether or not Daddy Long-legs are the most poisonous spiders. It is possible that they are the most poisonous spiders, but it hasn't been found out.

  • Of course, if it has never been investigated, the chances of it being the most poisonous, out of the at least thousands of types of spiders, is rather small. Jul 25, 2011 at 23:05

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .