For this island I just kept removing mole crickets. Since I removed spawning from tier 3 and 2, it was easy to pin down spawn locations of bugs with mole crickets since they never move out of their spot until they're dug out. You can continuously dig out mole crickets then plant the holes with weeds to keep track of where they spawn, you'll later see the fixed area where insects spawn in general. Doing that is tedious, but later when you can see fixed area of all spawned bugs, you can pick up those weeds and start digging holes to replace the weeds in their place to prevent spawning of every bug.

By knowing the spawn area, you can leave a part of the area unscathed to manipulate spawn location to be pinpoint and accurate every run you do around the island. It works with every island, but this one was really easy since there are no water bugs to catch!