Body to 9 mm; body white, with distinctive wood fibre-filled gut. Head capsule light brown-yellow with slightly darkened postoccipital margin, black mandibles, and dark brown-black mentum.
Dorsal surface of head comprising frontal apotome, a single sclerite bearing S2 and S3 comprising clypeus + labral sclerite 1, separated from anteriormost, elongate, narrowed sclerite 2 (bearing Sl). Sclerites 3, 4 and 5 not differentiated.
Antenna five-segmented, AR 1.7–2.0; blade annulate, extending well beyond antennal apex; style/peg sensillum placed subapically on second segment, extending to mid-fourth segment. Lauterborn organs absent. Ring organ in basal quarter of segment 1, with two adjacent pits.
Labrum with SI simple, lanceolate, arising from stout adjacent bases; SII and SIII simple, bases adjacent to each other, posterior to SI bases; short SIVa & b posterolateral to SIll base. Pair of spinulae arise close to base of SII, simple. Labral lamellae absent, or perhaps represented by cluster of few minute tubercles in mid-labrum; labrum strongly extended anterior to SI setae in smooth plate with scalloped anterior margin. Epipharynx with three rounded lobes forming pecten epipharyngis; three pairs of robust chaetulae, posterolateral pectinate, anteromedial simple; with two small chaetulae basales. Premandible dark, broad and blunt, with one apical tooth, without brush. U-sclerite strongly sclerotized.
Mandible heavily sclerotized, with outer and inner margins smooth, with long apical tooth subequal to width of three inner teeth (no evidence of any outer, dorsal tooth); three inner are evident; with four pairs of lateral teeth, third teeth of which innermost is smaller, and partly and fourth subequal in size; without evidence of fused to darkened mola from which narrow, narrow, terminally trifid seta subdentalis arises and extends to second inner tooth. Seta interna with 4–5 narrowly serrate branches.
Mentum with elongate anterior-projecting, paired median teeth separated by U-shaped cleft in which two small, blunt teeth are evident; with four pairs of lateral teeth, third and fourth subequal in size; without evidence of ventromental plates or beard.
Maxilla lying dorsal to sclerotized, anteriorly-projecting cardo, palpiger with well-developed maxillary palp, numerous fine, hyaline, simple galear lamella, basally (underlying cardo) with sclerotized transverse ridges; without pecten galearis; lacinial chaetae all serrate, numerous and dense, without differentiated antaxial, anterior lacinial or appendix on mesal margin (the posteriomost chaeta may represent an undifferentiated appendix).
Body not setose. Anterior parapods separate, with crown of yellow serrate claws and simple spines. Posterior parapods separate, with apical group of simple mid-brown claws. Procercus slightly wider than long, lightly pigmented, bearing 2 strong and 8–9 pale yellow anal setae. Supra-anal setae strong, appreciably longer than simple, short, cylindrical anal tubules.
The larva of Elpiscladius shares a characteristic anterior-projecting, medially deeply-incised mentum with Xylotopus Oliver, and resembles that genus in other features including the mandible shape and the five-segmented antenna lacking any hyaline division of the second segment. However, the absence of labral lamellae, the simple (not plumose) labral S1 setae, and the structure of the dorsal head sclerites differ, as does the absence of the marginal setal tufts on the body that characterize Xylotopus. The location of cephalic setae S2 and S3 on the same sclerite, considered to represent fusion of the clypeus with labral sclerite 2, is unusual but, given the range of conditions observed in the Brillia group, is unlikely to be diagnostic.
Larval Elpiscladius mine in soft immersed wood in montane (Cape Fold Mountain) streams of the Western Cape of South Africa (Cranston, 2008).