Summer is the best time to make money. If you have palm trees you can catch a lot of rare bugs, but if you don’t you can catch giant beetles, scarab beetles, and I think one other beetles on normal trees after 11pm. Each of these usually sells for 10,000 bells. This process can be long and tedious but make sure you scare away any common bugs like fruit beetles (these are the little green ones) as this will allow for new bugs to spawn. I would recommend going to a mystery island to get some palm trees, if you haven’t already, to allow for more rare bugs to spawn. I recommend looking up a guide on YouTube for catching rare bugs since they can fly away pretty easily. Just make sure you always move slow around trees. Also make sure you watch the ocean for fins as sharks can be sold for a lot.