Iowa’s Most Well-Known Spider Isn’t Really a Spider
Daddy longlegs are indeed arachnids – they have eight legs, but not all arachnids are spiders. The arachnid family includes spiders, ticks, mites, and even scorpions. The Daddy longlegs you typically find outdoors are actually Harvestmen – they can’t make webs and have no fangs to bite with. The worst thing a Daddy longlegs can do to people is give off a foul smell as a defense mechanism.
Perhaps you've heard the tale that "Daddy longlegs are extremely venomous but their fangs are too short to break through human skin."
Is that true?
The Pholcidae Daddy longlegs (cellar spiders -- mainly found in homes) are venomous and do have short fangs, but their structure does not allow them to bite humans. One of the most common kinds of Pholcidae is completely gray, while the other has a brown stripe on its belly. They are venomous and spin webs.
Scientists have documented roughly 6,500 species of Harvestmen. You'll find them on every continent except Antarctica.
They also have 3 body sections, not two like spiders, and their legs have seven sections which they can break off to surprise or distract a predator.
They do not produce silk so you won't find them on webs. Some cellar spiders are also called Daddy longlegs, but they produce silk.
They also have only one pair of eyes -- most spiders have 8 eyes.
The International Union for Conservation of Nature (IUCN) lists 21 species as threatened, with 14 as endangered or critically endangered. Five species are already extinct.
Opiliones fossils (Harvestmen) date back to 400 million years and have barely changed at all over that time.
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