It's a Bug/Ground-type Pokemon, so check the Weakness Chart to find out how to beat it. Nincada is the other Pokemon that learns Dig and you can only find it on Route 116. Pokemon Ruby Game Cheat: Capturing Nincada There's a problem though, at Level 35 it will try to evolve into Vibrava and, if it does, it won't learn Dig! When it levels to 35 and starts to evolve, press B to interrupt the evolution and stop it. The good news is they're easy to find once you get there! Once you have one, start leveling it up and, at Level 41, it will learn Dig. The Trapinch Pokemon is a desert-dwelling Ground-type Pokemon that is only found in two locations, Route 111 and the Desert Ruins. Pokemon Ruby Game Cheat: Capturing Trapinch Here's how to capture them and how to get them to learn Dig.
But, there's a way to fix the problem! There are two Pokemon that can learn TM Dig - Nincada and Trapinch. Ouch! That sucks, especially because you only get one TM Dig in the entire Pokemon Ruby game.