The relationship of feeding behavior of biting midge larvae to morphology of mouthparts is discussed. Herbivorous larvae have toothed, scooplike mandibles; short, flat maxillary palpi; short, broad labra; heavily sclerotized pharyngeal sclerites; and crenulate hypostomata. Predatory larvae possess thin mandibles with fossae; long, cylindrical maxillary palpi; projecting, thin labra; less heavily sclerotized pharyngeal sclerites; and smooth hypostomata. Generalist larvae possess mouthparts of an intermediate type.