What insect lays eggs that end up inside tomatoes?

Some of our tomatoes have pockets of insect eggs on the INSIDE of the tomatoes and some eggs have already hatched into tiny long, very thin black bugs (look like little pieces of black thread) between 1/16" and 1/8" long. Help! What can we do? They're not in all the tomatoes, not in the romas or cherries, but, so far, are in some of the beefsteaks and possibly an early variety as well. They are also not in all of the tomatoes on one plant either, just some. The outside of the tomato looks fine until you cut it open and see these light brownish colored pockets with either the eggs or the little bug slivers that move around. We have lots of plants (40 or so) and don't want to loose all our crop. HELP! I have been unable to find any info online.