Medium-sized larvae, up to 7 mm long. Red larvae, head capsule pale except darkened mouthparts and occipital margin.
Frontal apotome separated from slightly narrower, anteriorly tapered clypeus; labrum present, remaining labral area fragmentary. Without frontal fenestra.
Antenna with 5 segments, diminishing in size distally Lauterborn organs less than 0.3 length of segment 3, opposite on apex of 2nd segment, with short style. Ring organ near base of segment 1, seta absent. Blade slightly shorter than flagellum.
SI short, apically broadened and plumose only apically; SII slender, feathered apically on both sides; SIII short, slender; SIV normally developed. Seta premandibularis branched. Labral lamellae normal. Pecten epipharyngis divided into 3 parts, each plate with few (3-4) uneven distal teeth, without further teeth on surface. Premandible with 2 major and 1 minor teeth.
Mandible with strong pale dorsal tooth, apical tooth robust, with 3 inner teeth, separated by large notch separating inner teeth from dark mola. Pecten mandibularis strongly divided. Seta subdentalis inserted on ventral surface, simple, long. Seta interna inserted on dorsal surface, plumose, multi-branched.
Mentum with distinct dorsomentum of 3 subequal median teeth; 6 pairs of lateral teeth on each side, with 1st much lower than median or 2nd, then evenly decreasing in size laterally; 6th lateral may be reduced to near absence. Ventromental plates medially connected to median mentum, and thus separated medially at least by width of median section, relatively narrow and strongly curved to semi-lunar, with smooth anterior margin; striae distinct and continuous. Setae submenti simple.
Lateral and ventral tubules absent. Anal tubules short, without constrictions.
Adults and pupae of Endotribelos resemble Phaenopsectra, but the larva is reasonably distinct by virtue of the arched mentum shape and the diastema (gap) between the mola and the first (inner) mandibular tooth (at least in the Nearctic).
The larva of Endotribelos hesperium is associated with macrophytes in s.e. and s.w. USA (Florida, Alabama, California). Grodhaus (1987) found larvae within leaves of Typha and Sagittaria within which they construct tubes (like Endochironomus) but appeared to not damage the living leaf tissue. Grodhaus cites evidence for one or more further species in the USA, but none have yet been distinguished. Epler questions the identity of the Florida specimens, which are unreared. A named species, Chironomus lucens, originally described from St. Vincent (West Indies) could represent a Carribean Endotribelos (Grodhaus, 1987). The genus is reported from Central America (Sublette and Sasa, 1994; Epler, 2001) and from Brazil (Roque et al., 2003). There are records (also from Brazil) of larval Endotribelos being amongst the most important colonisers of immersed leaf litter, and of an Endotribelos larva living externally on a Trichopteran (Leptoceridae) (Roque et al, 2004).