Feltiella acarisuga is a gall midge for two-spotted spider mites, similar to the aphid predator Aphidoletes. The adult midge lays yellow-coloured eggs near spider mites. After about two days, a brownish yellow color larva hatches, which feeds on the mites.
After about a week, the larvae turn into a pupa covered with white fuzz, usually near the midrib of the leaf. The total life cycle varies with temperature, but generally takes about 2 to 4 weeks.