how can you tell the difference between serradigitus/vaejovis/paruroctonus?

title says it. i know they are closely related (at least the vaej and serr), and i don't have a trained eye quite yet. what can i look for? species in question: v. confusus, s. wupatkiensis, and p. boreus. found in eastern UT. thanks!

From the links section:

Key to the Genera of North American Scorpions

You'll probably have to have a specimen immobilized under a microscope to use this key, though. I recommend placing one inside a ziploc bag with little air in it (don't worry, it won't suffocate) so the bag stays flat and keeps the scorpion immobile. You can also flip it over this way to examine it from the other side and it won't be able to right itself.

I cant kinda eyeball it but its very hard. I reccomend you look for Luc to answer this one.

For anything North American, 1st choice Kari, 2nd Zach, 3rd Luc..
You can find them Here or on the ATS site.