OH WOW. There's money in bugs. LOTS of money. Like 60,000 per pocket type money. I had no idea.
The trick is to go beetle hunting at night. Just bopping around catching any old beetle has gotten me from around 20,000-30,000 each pocket full, but the real money is down by the shore. My entire coast is lined with palm trees, and every beetle that appears on one of those is worth 8,000 each. Combine that with all the other stags and whatnot, and a few scarabs or jewel beetles and you're looking at some real cash. Plus when you're by the shore there's a chance to catch a shark, and when you're by the river you can catch a few eels. SO MANY BELLS.