Small to medium-sized larvae, up to 6 mm long.
Antenna with 5 segments; segment 3 usually short, often much shorter than fourth. Antennal ratio often greater than 1. Ring organ large. Blade as long as or longer than flagellum. Lauterborn organs large, longer than antennal segment 3.
Labrum with SI plumose; SII and SIII simple but often strong; SIV stronger developed than usual. Labral lamellae fused at base, apically smooth or serrate. Chaetae simple or serrate. Pecten epipharyngis consisting of 3 simple, very short spines. With 6 pairs of simple, strong chaetulae laterales; chaetulae basales deeply split with fine points. Premandible with 2 larger and 1 smaller teeth; brush absent.
Apical tooth shorter than combined width of 3 inner teeth. Seta interna with 6-7 simple and serrate branches.
Mentum with 1-2 median teeth and 5 pairs of lateral teeth. Ventromental plate conspicuous, normally extending beyond outer tooth of flattened mentum; often with second plate lying inside main plate; beard absent.
Maxilla with pecten galearis absent. Anterior lacinial chaetae broad-based, broader than the other, usually broad, lacinial chaetae.
Body with anterior parapods with smooth, relatively short claws. Preanal segment curved over remaining segments, directing procercus with anal setae posteriorly and posterior parapods ventrally. Procercus mostly longer than wide with 3-7 short anal setae. Anal tubules slightly longer or shorter than posterior parapods; with or without several constrictions. No distinct body setae present.
Larval Paraphaenocladius may not be separable in entirety from Parametriocnemus - the curved preanal segment, directing the anal setae posteriorly rather than dorsally, may not be either universal or may even be artifactual. No Parametriocnemus has the secondary ventromental plates of many Paraphaenocladius; likewise Parametriocnemus always has 3 premandibular teeth, Paraphaenocladius has 2-6 teeth.
Most larvae of Paraphaenocladius are terrestrial, in damp soil, meadows, springs, and "alder carr". The genus is reported from Holarctic and Afrotropical regions. A revision is awaited.