Small to medium-sized larvae, head capsule relatively small.
Antenna longer than 1/2 length of mandible; 4 segmented although some figures suggest 5; segment 2 as long as first; terminal segments reduced. Blade well developed but not longer than flagellum. Weak Lauterborn organs present.
Labrum with SI plumose, each branch strongly incised; remaining S setae simple; SIII weak. Labral lamellae absent. Premandible with 2 apical teeth and variably developed inner tooth; brush absent.
Mandible with apical tooth shorter than combined width of 3 inner teeth. Seta subdentalis present but small. Seta interna with some terminally serrate branches.
Mentum with single median tooth that may be domed or with median nipple; 5 pairs of lateral teeth present. There may be a projection or small tooth at base of outermost mental tooth. Ventromental plate weak, without setae beneath.
Maxilla with sensillae on palp and galea reduced. Few lamellae present on base of palpiger, none on galea (possibly always). Setae maxillaris simple, reduced in number and size. Palp partially divided into 2 parts.
Body with anterior parapods basally fused, with numerous fine spines on basal part and several simple claws at divided apex. Posterior parapods reduced but separate and bearing simple claws. Procercus absent; no anal setae present. Anal tubules reduced but usually visible.
Larval Smittia are almost exclusively terrestrial, with S. aterimma particularly abundant in damp soils and compost heaps, and perhaps able to damage horticultural crops. One species is aquatic.
The genus is worldwide in distribution.