Science Q&A: Are Daddy Longlegs Poisonous?

By Lindsay Nemelka

Science Editor

Photo: taken from Wikipedia, Opiliones Harvestman by Bruce Marlin

Growing up I always feared spiders. They can squeeze through impossibly tiny cracks, scurry and jump, leave nasty sticky webs and have way too many eyes for my comfort. I was always on the lookout for spiders on my back patio as a kid; but the fearsome ones weren’t the big hairy jumping spiders or the yellow crab spiders—it was the daddy longlegs that I feared the most. Something about those long spindly legs freaked me out.

Somewhere in my childhood I was told that the daddy longlegs were among the most poisonous spiders in the world, but thankfully their fangs were too short to bite humans. I have carried that notion with me through adulthood and it wasn’t until recently that I discovered that daddy longlegs aren’t poisonous at all (at least partially).

Spider or not a spider?

(1) four pairs of legs
(2) cephalothorax
(3) opisthosoma (abdomen)
Spider image from CDC Public Health Image Library

There are actually two groups of animals that are called daddy longlegs. Both are in the class Arachnida (along with scorpions, ticks and mites) but one is a true spider and the other is not. The creature most commonly referred to as daddy longlegs have a single body segment instead of the two which classify spiders, two eyes and eight legs attached to the fat round body. These creatures don’t produce silk, so they can’t form webs and have long legs that can flex and bend. These daddy longlegs, also called Harvestmen, are classified in the Order Opiliones.

The other daddy longlegs are true spiders and are in their own Order and Family: AraneaePholcidae. These spiders have two body segments with the eight legs attached to the forward segment-the cephalothorax, while silk is produced from the abdomen. Legs of spiders are not bendy but have joints. Spiders have eight eyes located at the front of the head. The common name for these animals is long-legged cellar spiders, which are seen more often around homes and basements.

Why the confusion?

Macro shot of Opiliones Harvestmen. Probably male Phalangium opilio by Mehran Moghtadai. Taken from Wikipedia.

Daddy longlegs (Opiliones) – These arachnids are opportunistic predators though they mostly eat decomposing plant and animal material. They don’t produce venom because of their lack of fangs and venom glands. However, there is a difference between “venomous” and “poisonous.”Venomous animals inject toxins into their victims, while poisonous animals secrete toxins when touched or eaten by predators (like a crane fly). Some Opiliones secrete material that can be poisonous to small animals when eaten, but they do not inject venom into their prey.(There have been no reported cases of humans ingesting the spider and getting sick either.)The tale that these daddy longlegs are one of the most poisonous spiders is clearly false.

Daddy longlegs spiders (Pholcidae) –Although these spiders have fangs and inject venom into their prey like other spiders, there has been no report of one biting a human and having any detrimental effect. If these spiders were deadly poisonous to humans, the only way scientists could find out is by sampling the spider’s venom and injecting it into a person. For obvious ethical reasons this has never been done before, neither has there have been no toxicology studies conducted of the daddy longlegs poison. Pholcids do in fact have very short fangs called an “uncate.” These spiders rely on a secondary tooth that meets the fang like a pair of tongs. Other spiders that have uncates are able to bite humans, such as the Brown recluse, but Pholcidae don’t use their fangs as much during hunting because they prefer to wrap their prey.

Pholcus phalangioides, Dresden (Saxony, Germany), picture taken by Olaf Leillinger, taken from Wikipedia

True or False?

Daddy longlegs in the Opilionids Order certainly don’t live up to this myth because they do not have venom or fangs at all. Though they may be poisonous when ingested by small creatures, their poison doesn’t compare to, say, the poison dart frog in South America.

The daddy longlegs spider’s venom has never been studied, so the tale that they are extremely poisonous is based on unknown facts. These spiders do have short fangs, but not any shorter than other spiders that are known to bite humans.

In short, the myth that daddy longlegs are deadly but don’t have long-enough fangs to bite humans is false.

So What Is the Most Venomous Spider?

There is differing evidence to fully answer this question. In the realm of spiders, the black widow and the brown recluse are among the most dangerous to humans. The most venomous spider in the world was named the Brazilian wandering spider by Guinness World Records in 2012.

Brazilian Wandering Spider, taken from Wikipedia, photo by Techuser


Check out the world’s 5 most venomous species, and the 10 most poisonous spiders on earth.


3 thoughts on “Science Q&A: Are Daddy Longlegs Poisonous?

  1. Im so dumb for believing that there deadly😡💔👿=🔥🔥🔥🔥🔥✌🔥🔥🔥✌🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥

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