SOS Encounter: Route 1
Walk: Route 1 (20%)
Its base catch rate is 255 out of 255 (higher is easier); the catch rate calculator works out your odds with each ball. For the look, the best colour match is Friend Ball or Nest Ball.
Evolution: Spinarak → Ariados (Level 22).
Spinarak in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)