Where to catch Ariados

In Kitakami (Scarlet & Violet – The Teal Mask)

• Fellhorn Gorge — Walk
• Kitakami Wilds — Walk
• Mossfell Confluence — Walk
• Timeless Woods — Walk

In Johto & Kanto (Gold, Silver & Crystal)

• Route 2 — Walk
• Route 37 — Walk

Ariados — full Pokédex entry