This is kind of a weird question.
I noticed while grinding on the Tropical Island that I went long bouts where all I would see was Fruit Beetles and Wharf Roach. I was ignoring them since they are only worth 200 and 100 bells each. While ignoring them not much else would show up until I actively chased them away. There was also a period of time where I didn't see much of anything new until I noticed a Horned Hercules on a tree in the back that I had not checked in a while.
For example, if I ignore too many Fruit Beetles and Wharf Roach's are other bugs going to stop showing up because there are too many bugs on the screen.
Or if a rare bug has spawned, are other bugs less likely to spawn because the valuable rare bug is taking up the allotted 'bug worth' available for the Island at the moment.
So I was wondering if anybody knows of a 'bug formula' that limits what can be on screen at any one time? Of course it could also just random and I am just seeing something that isn't there in my frustration.