No, there's an actual nightmare island with a shitload of tarantulas on it.
You can walk up to them slowly, stopping when they rear up. Or you can dig a trench with a gap in the middle, and run up that. If they follow you in, you jump out the back. If the get stuck on the outside, it's easier.
Flick is the visitor that buys bugs for 1.5x the price, or can take three of one type on insect and make a model of it. His fish equivalent is CJ.
Tarantula Island is a special Nook Miles island that spawns infinite tarantulas, so you don't have to trick the game into doing it.
Thank you both!