What's the difference between Spiders, Solpugids, and Amblypygi?

Abu Bakr

Arachnopeon
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I know all three of the above are arachnids but belong to different orders. I wanna know, what makes something a spider? What's the definition of a spider and how do solpugids and amblipygids don't fit the criteria of a spider?

It would be great if someone quotes the definition of Spiders, Solpugids, Amblypygi, and scorpions from some arachnology book if they can.

I'm having a debate with someone so I need this info.

Thanks.
 

sezra

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i thought there might have been a definition in my copy of the Spiders of Britain and Northern Europe (Collins Field Guide), but i dont think you are going to get such a clear cut definition.

the following page lists some differences, but the chapter on spider biology is pretty long.

If you open the picture in a new page you should be able to read it.
 

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AphonopelmaTX

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The easy and clear cut answer is that spiders are arachnids with two body segments separated by a narrow waist called a pedicel and produce silk. No other arachnid order has these two features. I'll emphasize the "produce silk" part. ;)
 

The Snark

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I wanna know, what makes something a spider?
Eight legs, chelicerae, venom glands, spinnerets, web glands, divided body with pedicel = Mesothelae, Mygalomorphae or Araneomorphae which are termed 'spiders'.
The other orders do not possess all the correct components.
 

chanda

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Eight legs, chelicerae, venom glands, spinnerets, web glands, divided body with pedicel = Mesothelae, Mygalomorphae or Araneomorphae which are termed 'spiders'.
The other orders do not possess all the correct components.
While it's true that most spiders possess venom glands, it is not an absolute requirement in order for something to be considered a spider. The Uloboridae are non-venomous spiders that rely on cribellate silk to capture their prey.
 

AphonopelmaTX

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I remember reading once that some Mesothelae may not have venom as well
This was found to be false. See the following...
Foelix, Rainer, and Bruno Erb. "Mesothelae have venom glands." Journal of Arachnology 38.3 (2010): 596-598.

If you want to learn about a truly unique spider, Micromygale dibelmma (Platnick & Forster, 2982) is a mygalomorph with only two eyes and no lungs! :wideyed: See...

Platnick, N. I. & Forster, R. R. (1982). On the Micromygalinae, a new subfamily of mygalomorph spiders (Araneae, Microstigmatidae). American Museum Novitates2734: 1-13.
 

Biollantefan54

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Ah, interesting, thank you for the information! I will definitely look that one up!
 
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