Giant beetles do not come out until 11.00 PM.
They are found on the fruit or regular trees in the center of the island, if you haven't chopped them down.
Yes, I always leave one tree in the middle as I usually go to the island late at night, I find it a relaxing way to end the day.
I also like shaking the trees late at night. The bees are easy now you can shake the trees carrying your net and a bee plus hive is three thousand bells, plus the coins and the furniture. I can also chat to villagers, move flowers that they have planted in the wrong place and enjoy a mooch around the town at the same time. It's another late night thing I find relaxing and profitable.