Answer: It sounds like tomato pinworms. These insects are mostly a problem in California and the South. They are difficult to control, because they spend so much of their time hidden and protected from sprays. As soon as you see signs of the insect, spray with B.t., a biological control, every three to five days until the infestation is under control.
Here is a site describing the insect's life cycle.
This site further describes this pest problem.
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