Anyway, i have all the advanced secrets on beetle finding.
Here's the steps:
1. Get the island
Wait until 5pm, then:
2. Go to the island, and talk to the little gyroid
3. Get all the tools but the wetsuit
4. Get rid of everything on the grass, even flowers
5. Get rid of all the trees at the bottom of the island on the sand
6. Cover the whole grass area in holes so other bugs don't spawn
It should be 6-7pm now. If it isn't, go fishing, and sell everything but Blue Marlins and any sharks but ocean sunfish to the turtle kid. Ocean sunfish are worth 4,000 bells, and the cheapest beetle we'll be catching is 6,000 bells.
When beetles start appearing, get rid of you shovel and axe.
When you see those annoying little grey bugs, almost hit them with the net so they scuttle away then fade into the sand.
How to catch the beetles
1. Dig a hole in front of the trees
2. Hold down A and walk up. (You can walk until you are about 5 paces from your holes, or it seems to put the beetles off, and they will fly away effortlessly) Stop every once in a while briefly for difficult-to-catch ones like golden stags
3. Let go of A, and you'll catch the little guy
Every once in a while, check your pockets to see how much room you have left. When your pockets are full, put all your beetles in the box. Repeat the above steps along with the thing about the box i just said until your box is full.
If you encounter a shark
If you encounter a shark, catch it. That's all there is to it. Remember to sell the sunfishes to the turtle kid.
So there, i hope i taught you something about beetle farming. If you have any other tips, say so in the comments and i'll add them!