All you have to do is tame a scorpion and ride up to an arthro on the scorpion and feed it spoiled meat. The arthro will not aggro on you while you are riding the scorpion. I did this on my mobile world so I can confirm that this works at least on mobile.
Easiest and safest way to tame this is to lure it under water. They stop aggro and you can tame as you please. Just make sure you come up for air every once in a while. Also be sure the water is deep enough.