Small larvae, to 3 mm long.
Antenna with 5 segments on prominent pedestal without basal tooth or spur. Antennal ratio 1.2-1.3. Ring organ basal on 1st antennal segment. Seta lacking but may be broken off in described specimen. Lauterborn organs large, on broad pedestals extending to near antennal apex, inserted opposite on apex of somewhat wedge-shaped 2nd segment. Subsequent segments shorter than 2nd. Antennal blade usually extending no further than apex of 3rd segment, accessory blade fused to blade, short. Style on apex of 2nd segment, shorter than segment 3.
SI seta comb-like, fused at bases, SII on large pedestal, plumose, SIII short, simple, SIVa present. Labral lamellae well developed. Pecten epipharyngis 3 simple, finger-like lobes. Premandible with 2 teeth, brush strong.
Mandible with brown dorsal tooth apical tooth and 2 inner teeth, with additional small brown tooth on dorsal surface. Seta subdentalis long, curved, not reaching tip of apical tooth. Seta interna of 4 plumose branches. Pecten mandibularis well developed with many long lamellae. Outer margin of mandible with pronounced hump.
Mentum with simple rounded median tooth 5 pair of laterals, median 3 teeth of even height and set forward from remaining teeth. Ventromental plates close together medially, subequal in width to mentum, with fine striae.
Without tubules. Claws of posterior parapod numerous, all simple.
A very characteristic genus with several species. The form of the pecten epipharyngis distinguishes the larvae from all other genera except for Lithotanytarsus and Paratanytarsus. However, larvae of both of these genera have Lauterborn organs which are either sessile or are borne on very short pedicels, whereas those of Sublettea are carried on pedicels which reach almost to the antennal apex.
So far Sublettea is found in cool, clear, fast flowing streams and rivers.
The genus is Nearctic and Oriental in distribution. The only described species, S. coffmanni, is known from USA and Canada.