Basically anywhere. I usually bring a couple hundred clumps of weeds along with me just so I can plant anytime I hear the incessant chirping.

 How can you tell which are their regular spawning sites? Won't they just spawn somewhere else?

I've just seen another scorpion but it didn't even see me and just committed suicide off the rock and into the sea. Fml :( I have caught a coelacanth tho

You're not doing anything wrong. They nerfed the rare bug spawn rate with the april update. Just gotta keep grinding.

For mole crickets I just plant weeds on their spawning sites. Much easier than hunting them down and digging. They can't spawn where there's plants.

No scorpions, just mole crickets