What is eating my Japanese maple?
This looks like it is likely damage from June beetles. June beetles are like Japanese beetles in a lot of ways -- they live underground most of the year as grubs, then come out of the ground as adults in summer. The difference is that Japanese beetles are usually more of a problem as adults than as grubs, whereas June beetles are the opposite. It's rare that they cause much damage as adults. Your situation may be the exception to the rule.