Good evening.
My understanding is that if you can see that something is there, just can’t see it clearly without a magnifying glass or the like, it is considered to be visible.
Think about a fig. It is many small particles (for lack of a better word) that provide many, many crevices. So the bugs enjoy the dark corners and crevices.
I heard a shiur from Rabbi Yosef Eisen shlit”a, who is recognized as an expert in bedikas tola’im. He said that the minimum amount of issurim for eating a bug is 4. Something to think about.
May HaShem protect us from eating anything unkosher of any kind or type.