What's making holes in my Japanese Eggplants?

Hi. I've got a Japanese Eggplant plant that seems to be doing really well. The problem is that by the time the eggplants are big enough to pick, they all have one or two holes bored in them.

The holes look like this:



Sometimes the hole is sealed over, like this:



I've never found a worm or parasite in any of the holes, just the holes themselves.

What's causing them, and what can I do about it? I've heard of "flea beetles" that make holes in eggplant leaves, but the leaves of the plant seem fine.

Thanks in advance!