Hermit crab

The hermit crab is a bug you catch disguised on shoreline. In the northern hemisphere it is around all year, from 7 PM – 8 AM. Nook's Cranny pays 1,000 Bells, Flick pays 1,500 Bells.

Looks like a seashell on the beach at night, until it starts walking. If a shell seems to wander, sneak in with the net raised, then sell it to Flick for 1,500 Bells.