You must have the following:

1. Access to the Island
2. Access to Re-tail (If it's closed, you'll need to store your hauls.)


First of all, talk to Kapp'n and head out onto the Island any time between 7PM and 4AM.


Next, head out onto the island proper. Talk to the gyroid to get the fishing rod, shovel, axe, and most importantly, bug net. Now, normally, there will be flowers, hibiscus bushes, and regular trees on the island, as well as tropical tress on the beach. Most of this stuff will give you bugs that aren't worth very much at all, taking up the slots of the "spawn limit" set in place on the island. There will be 4-6 bugs on the island at any given time. If all these slots are be taken up by worthless bugs, you'll be wasting time and space with trash, basically. What we want are the most rare and valuable bugs the game has to offer, and they all spawn on the island. the very large majority of them being humongous beetles. The one exception is the Emperor Butterfly, which will show up from time to time also. Now that I have explained what we need to accomplish, let me tell you how we're going to accomplish it.

First, whip out that trusty shovel and axe, and get rid of everything that's not a tropical tree. Yes, I said everything. You can put it back the way it was with minimal effort at a later date if you so choose. Now, this should leave you with a large patch of grass in the middle, and a ring of palms, around the outside on the beach. This is what we want. Now, take out your bug net, and catch every beetle you see hanging off the side of a tree, while scaring off the hermit crabs, warf roaches, and Tiger beetles by slamming down your net next to them. It would also do well for you to catch any fish that have a finned shadow. Most likely these will be some form of shark, which sell for more than your average beetle. They are a rare spawn, so don't go out of your way to search for them. Just nab them when you get the chance. You will be surprised how quickly your pockets will fill. Fill up the deposit box in the cabana/lobby with beetles and sharks, being sure to use all four pages. Head back, and sell to Re-tail. You should net yourself at least 300K bells each trip.

Enjoy.