It's a fact that gets passed around like a party trick: daddy longlegs are supposedly the most venomous spiders alive, saved from being deadly only by fangs too small to break human skin. Specific enough to sound credible, which is exactly the problem. 'Daddy longlegs' actually refers to two unrelated creatures, harvestmen and cellar spiders, and neither one backs up the extreme-venom claim attached to the legend. The fangs-too-small excuse doesn't need to exist, because the venom part was never true to begin with.
What you were taught
Daddy Longlegs are the most venomous spiders but can't bite humans
What we know now
"Daddy longlegs" is a nickname, not one animal. Harvestmen are arachnids without venom glands or fangs. Cellar spiders are true spiders with mild venom and can bite humans, but there is no evidence they are the most venomous spiders on Earth. The fangs-too-small story is folklore, often attached to the wrong creature entirely.
Updated understanding emerged around 2020
No. Daddy longlegs are not the most venomous spiders on Earth, and the "fangs too small to bite you" excuse does not save a legend that was never true.
The trouble starts with the name. "Daddy longlegs" gets slapped on harvestmen, cellar spiders, and crane flies, which are three unrelated animals. Only cellar spiders are actual spiders with venom. Harvestmen do not have venom glands. Crane flies are insects. None of them supports the playground boast.
Someone at camp, or in the back row of biology, delivered the line with confidence: daddy longlegs would be deadly if their fangs could reach you. It sounded like a secret the textbooks forgot, specific enough to repeat.
The version you heard might have pictured a spindly creature in the grass. It might have meant the pale spider in the basement corner. Same nickname, different animals. That ambiguity is load-bearing. The myth survives partly because listeners fill in their own daddy longlegs and never check which one the speaker meant.
Rick Vetter, a retired entomology researcher at UC Riverside who has spent years batting this myth down, starts with the same question: what are you calling a daddy longlegs?
Cellar spiders (family Pholcidae) are the true spiders in the bunch. Two body segments, eight eyes, fangs, venom ducts. They build tangled webs in corners and basements.
Harvestmen (order Opiliones) look spider-ish from across the room. One fused body segment, two eyes, no silk, no fangs, no venom glands. Their mouthparts pinch and tear; they scavenge more than they stalk.
Crane flies (family Tipulidae) are insects: wings, long legs, often mistaken for giant mosquitoes. Many adults have no mouthparts at all and cannot bite.
The Burke Museum in Seattle puts it bluntly: three unrelated groups share the nickname. Only one is a spider.
Start with harvestmen. They are not venomous. When disturbed they may release foul-smelling defensive chemicals. That is poison by contact, not venom injected through fangs. UCR notes the stuff can bother small arthropods; it is not evidence of world-beating toxicity.
Cellar spiders do produce venom, like nearly all spiders. They can also bite humans. Vetter compares their fangs to those of a brown recluse, then stops the comparison there: he is not aware of any publication showing pholcid venom causes a toxic effect in people. One scientist who let himself get bitten reported a small dark mark for a day or two and moved on.
On a 2004 MythBusters segment, later discussed in a 2019 paper, arachnologist Charles Kristensen injected mice with venom from cellar spiders and from black widows. Black widow venom had the stronger effect. Burke Museum adds that a recent study found pholcid venom unusually weak even on insects. "Most venomous" does not show up in the data. It shows up in folklore.
"Daddy longlegs" is a nickname, not a species. Harvestmen are not venomous spiders. Cellar spiders are mild, corner-dwelling spiders that can bite but are not medically significant by any documented account we could find. Crane flies are not in the venom conversation at all.
The fangs-too-small defense was solving the wrong problem. The venom crown was never theirs to lose.
One plausible origin thread runs through Australia, where introduced cellar spiders have been seen killing highly venomous redback spiders. Observers may have assumed the hunter packed stronger venom. Playground logic and scary-story momentum did the rest. Vetter told UCR he thinks the myth spread because nobody had the taxonomy handy to refute it.
No. The claim is an urban legend. Cellar spiders (the actual spiders in the group) have ordinary spider venom that researchers describe as weak, not record-breaking. Harvestmen have no venom glands at all.
It depends which animal you mean. Cellar spiders can bite humans; documented effects are minor. Harvestmen lack fangs suited to biting people. Crane flies generally cannot bite.
No. They are arachnids, not true spiders, and they do not have venom glands or fangs. They may release defensive chemicals when disturbed, which is not the same as spider venom.
That line often gets pasted onto harvestmen, which do not have fangs or venom in the first place. For cellar spiders, fang size has been overstated: MythBusters demonstrated they can pierce skin, with a brief sting and no serious medical effect reported.
2010s · Science
2010s · Science
2010s · Science