Are Daddy Long-Legs the Most Venomous Spiders in the World?
"Daddy long-legs have the most potent venom of any spider in the world — they just can't bite you, because their fangs are too short." Almost everyone has heard some version of this, usually from a teacher, a camp counselor, or a nature documentary, delivered as flatly as any other fact of biology. It has been tested on live television twice. It is still wrong, and not in the usual exaggerated way spider folklore is wrong: the "daddy long-legs" in the story turns out to be three completely unrelated animals, and only one of them has venom at all.
The claim
"Daddy long-legs" — used loosely for the harvestman (order Opiliones), the cellar spider (family Pholcidae), or the crane fly (a large winged insect, not a spider) — is said to have more potent venom than any other spider on Earth, but fangs or mouthparts too short or too weak to break human skin.
Source trail
No source we found, including the field's own named expert, can say where the claim started. Rick Vetter, a retired research associate of entomology at the University of California, Riverside, told UC Riverside's own news office in 2022 (fetched directly, checked 2026-08-22): "That's a really good question, and I really don't have an answer for it," adding only that "somebody said [it] once and there was never enough knowledge to refute it. So it just goes on and on."
What is traceable is how the claim got tested — twice, on the same television show. A 2004 MythBusters episode ("Buried in Concrete, Daddy Long-legs, Jet Taxi," season 2, episode 13) let a cellar spider bite series regular Adam Savage on camera. A separate 2014 segment supplied lab-grade cellar-spider venom — produced by arachnologist Charles "Chuck" Kristensen's company, Spider Pharm — that fed directly into the first peer-reviewed chemical analysis of any pholcid venom, published in 2019. Nearly every current retelling collapses those two different segments into one story, and, in the case of the university whose own faculty co-authored that 2019 study, gets a detail of the study itself wrong doing it — see "What isn't," below.
What's confirmed
- Harvestmen have no venom glands at all — one-third of the myth is settled outright. Wikipedia's own Opiliones article, fetched directly (checked 2026-08-22), states in its "Misconception" section, citing entomologist May Berenbaum's 2009 book: "None of the known species of harvestmen have venom glands; their chelicerae are not hollowed fangs but grasping claws that are typically very small and not strong enough to break human skin." Berenbaum's book itself was not independently fetched by us.
- Crane flies have no venom and cannot bite either — a second third of the myth is settled. UC Riverside's own Spider Research page, fetched directly (checked 2026-08-22), and the Burke Museum's own "Spider Myths" page, fetched directly (checked 2026-08-22, written by Rod Crawford, the museum's Curator of Arachnids), both confirm crane flies have neither venom nor biting mouthparts.
- The cellar spider — the one true spider among the three "daddy long-legs" — does have real venom and fangs that pierce human skin, the opposite of the "can't bite" half of the myth. The 2019 peer-reviewed study (below) states that during the 2014 MythBusters test, a male Physocyclus mexicanus bit a human, with "a mild sting with no long-lasting effects."
- That venom, while real, is far weaker to mammals than black widow venom, confirmed by the first rigorous chemical study of any pholcid venom. Zobel-Thropp, Mullins and Binford (Lewis & Clark College), with Kristensen (Spider Pharm), Kronmiller (Oregon State University), and David and Breci (University of Arizona), "Not So Dangerous After All? Venom Composition and Potency of the Pholcid (Daddy Long-Leg) Spider Physocyclus mexicanus," Frontiers in Ecology and Evolution, published 12 July 2019 — fetched directly, checked 2026-08-22. The paper identifies over 120 proteins and peptides in the venom by proteomics and transcriptomics, and measures potency with a cricket bioassay (an effective paralytic dose of 3.9 μg/g on house crickets within 60 minutes) rather than a mammal test. Its own conclusion: bites are "inconsequential" to humans and other mammals, with "negligible toxicity" compared to black widow venom.
- The study's own accompanying press release confirms the 2014 date for the venom-supply collaboration, independently of the paper itself. The Lewis & Clark College release, republished by phys.org, fetched directly (checked 2026-08-22), states verbatim: "In 2014, Discover Network's hit series MythBusters took the liberty of dispelling the daddy long-legs myth with venom from the same species and overseen by Chuck Kristensen, a coauthor on this work; however, until Binford's paper was published, there had been no rigorous analysis of what is in the venom of any pholcid spiders."
What isn't
- Who started the myth, or when. Rick Vetter's own quote above is the closest anyone came to an answer, and it's an admission that no one knows.
- Whether the 2019 study tested mice or crickets — the paper and UC Riverside's own 2022 press page disagree, and we could not resolve it. The 2019 paper's own methods section, read directly, describes a cricket paralysis bioassay, not a mammal test. But UC Riverside's own 2022 news page — the same page quoting Rick Vetter above — states instead: "On a 2004 'MythBusters' episode that was later documented in a 2019 study, arachnologist Charles Kristensen reported injecting mice with venom of either cellar spiders or black widow spiders." We could not locate a mouse study anywhere in the primary literature we could fetch, and several other outlets covering the same UCR story (ScienceTimes, NatureWorldNews, and others) repeat the "mice" detail without independently checking it against the paper they're citing. We report the contradiction rather than picking a side.
- Whether "2004" or "2014" is the right date for the MythBusters segment tied to the 2019 study. A 2004 episode bit Adam Savage on camera, independently confirmed by the episode's own listing. The study's own press release instead dates the segment that supplied Kristensen's lab venom to 2014. These could be two different segments — a plausible reading, since MythBusters ran until 2016 and revisited myths more than once — but we could not independently fetch a MythBusters episode archive confirming a distinct 2014 airing: mythresults.com's own episode guide returned an access-denied response on every direct fetch attempt this session, so it's named, not linked or confirmed.
- Whether pholcid venom testing had genuinely "never been done" before 2019. UC Riverside's own Spider Research page (undated, no author named) states flatly that venom testing "has never been done" for ethical reasons, while the 2019 paper's own press release says only that no rigorous chemical analysis existed before it — a narrower claim, since the 2004 on-camera bite already showed a human being bitten. The undated page may simply predate 2019, but neither UCR page references the other, so the two statements sit uncorrected side by side on the same institution's own domain.
Verdict
Two-thirds of the myth collapses the moment you separate the three animals it conflates: harvestmen have no venom glands, and crane flies have neither venom nor biting mouthparts, so neither can be "the most venomous spider" or anything else. The one true spider among them, the cellar spider, does have venom and can bite — the exact opposite of the "fangs too short" half of the folklore — but that venom is far weaker to mammals than a black widow's, settled by the first rigorous chemical study of it in 2019. What's not settled is the tidy origin story: the university whose own faculty co-authored that study can't get its own 2022 recap of it to agree with the paper — mice versus crickets, 2004 versus 2014 — and no one, including the researcher most directly asked, can say where the myth began in the first place.