Small to medium-sized, up to 5.5 mm long. Body "pale". Eyes paired, contiguous, the upper round, the lower reniform.
Frontal or frontoclypeal apotome present (clypeus either fused or separate), with labral sclerite 2 distinct, other labral sclerites fragmentary.
Antenna with 5, 6 or 7 segments, basal segment slightly shorter to slightly longer than flagellum. Lauterborn organs large, alternate on apices of segments 2 and 3, short style immediately subapical on segment 3. Ring organ in basal 1/4 of segment 1, seta absent. Blade shorter than to equal length cf antennal flagellum; accessory blade short
SI slender, fimbriate only on inner (medial) side. Bases of SI on common base. SII slender, fimbriate at apex, each on low pedestal. SIII normal; SIVa normal. Seta premandibularis simple. Labral lamellae with uniform teeth. Pecten epipharyngis of 3 separated, apically toothed plates. Premandible with 2 apical rounded teeth.
Mandible with short, pale, erect dorsal tooth contiguous basally with smaller, flatter tooth on inner surface of mandible; apical tooth short and dark as are 2 distinct inner teeth, Mola with 0-2 spines Pecten mandibularis modestly developed Seta subdentalis straight, long and wide, bluntly rounded apically, reaching apical mandibular tooth. Seta interna inserted on dorsal surface, plumose, 4-5 branched.
Mentum with short, pale, low median tooth, and 5 pairs of lateral teeth; 1st lateral tooth notched, higher than middle tooth, with remaining teeth declining in height; lateralmost pair fused basally. Ventromental plates narrowly separated medially by 1-2x width of median tooth, about 2/3 to subequal to mentum width, curved and coarsely to finely striate, finer nearer median end, medially curved posteriorly. Setae submenti long, simple or apically weakly fimbriate.
Lateral and ventral tubules absent. Anal tubules short. Seta at base of procercus as long as anal setae.
Beardius belongs with a group of genera in which the Lauterborn organs are large and alternate on the apices of antennal segments 2 and 3. The antennal segment number can range from 5 to 7 in some neotropical species. Amongst this grouping, a mentum with the median tooth pale and lower than first lateral teeth, and mandible with 2 inner teeth and a dorsal tooth, is uniquely diagnostic for Beardius.
Beardius is essentially a meso-American and tropical neotropical genus with substantial diversity in Brazil, where several species are associated with immersed aquatic macrophytes. Three species of Beardius are known from Florida: B. truncatus, B. reissi and B. breviculus. Here Beardius larvae occur in inundated wet prairie habitats and other intermittent wetlands, solution holes (in the Everglades), marshes, streams and rivers (Jacobsen and Perry, 2000).