So we typically clean vegetable matter of bugs because, while it isn't an aveirah to eat a bug part if it's smaller than a(n) (halachic) olive, it is still prohibited to eat any non-kosher living thing as a whole regardless of size. How far does this extend though? Obviously we aren't concerned with microbacteria because those are impossible to see with the naked eye, but what are the machmir and makil opinions on this subject? How big does the bug have to be before it is required, by these opinions, to brush them off your veggies?
I don't know of any positions that forbid that which can't be detected using means that were available in ancient times (e.g. microscopic); nor of a position that would allow one to take an individual bug that is visibly a bug, albeit small, and eat it (or frankly, l'chatchila, even an individual bug part that is not part of a larger mixture). There is a range of positions, however, about when it is a concern in a taaroves (mixture) regarding how evident the bugs' presence have to be. See: http://5tjt.com/tropicana-orange-juice-an-update/