Route 112: 3 species in 3 games

Road 112: 3 species across 5 versions

Ruby and SapphireEmeraldOmega Ruby and Alpha Sapphire

Ruby and Sapphire: 2 species, all by walking in tall grass or a cave
Species	Levels	Chance	Game page
Machop	14 to 16	25%	All places
Numel	14 to 16	75%	All places

Emerald: 2 species, all by walking in tall grass or a cave
Species	Levels	Chance	Game page
Marill	14 to 16	25%	All places
Numel	14 to 16	75%	All places

Omega Ruby and Alpha Sapphire: 2 species, all by encountering 5 pokemon within grass, flowers, or within a cave
Species	Levels	Chance	Game page
Machop	8	35%	All places
Numel	8	65%	All places