Large larvae, up to 12 mm long. Dark red.
Frontoclypeal apotome with long to oval fenestra. Clypeus part fused to frons, with protruding anterior margin; labrum and lateral sclerites present.
Antenna with 5 segments. Ring organ in basal 1/4 of 1st antennal segment, seta absent. Lauterborn organs large, opposite on apex of 2nd together with style. Antennal blade not extending to flagellum apex, accessory blade very long, subequal to 2nd segment.
SI seta simple to weakly plumose, SII always simple; SIII short, thin, SIVa simple sensillum. Labral lamellae a relatively slender toothed plate, in D. rufipes deeply divided medially. Pecten epipharyngis an undivided plate with numerous teeth of varying lengths. Premandible with 2 teeth. Seta premandibularis simple
Mandible without dorsal tooth, apical tooth strong and long, with 2 dark inner teeth, an inner 'tooth' very narrowly separated from mola. Seta subdentalis simple. Seta interna of 4 toothed to finely plumose branches.
Mentum with median tooth simple or trifid, with 6 pairs of outer teeth, all teeth often worn by mining habit Ventromental plates short, medially separated by almost half width of mentum, striate across complete plate. Setae submenti simple.
Lateral tubules absent, 1 pair of moderately long ventral tubules present, curving under abdomen.
Both adult and immature characters indicate that Demeijerea is a separate genus. Glyptotendipes species group C is most closely related. Demeijerea larvae may be distinguished from the frequently similar larvae of Glyptotendipes by the labral sclerite 1 which is partially fused with the frontoclypeal apotome and by the possession of only 2, rather than 3 inner teeth on the mandible.
Larvae of Demeijerea mine in freshwater sponges and Bryozoa.
One species (D. rufipes) is known from the western Palaearctic and two definite species (D. atrimana, D. brachialis) are known from the Nearctic.