Larva to 3.5 mm long, with distinctively large head (to near 20% body length).
A single (?smooth) sclerite.
Comparatively long, slender, 4-segmented; Ring Organ subapical on 1st segment. Segment as long as 3 and 4 combined. Blade subequal to flagellum. Lauterborn organs absent. Style on apex of 2nd segment, well-developed, as long as segment 2.
SI seta adjacent basally, comprising long, slender; SII large and broader, arising from low pedestal, SIII anteriorly placed near midline of head, one anterior to the other (ie not bilaterally symmetrical); SIVA and B thin setae. Labral rod close to SIVB, strongly developed on pedestal. Chaetae, chaetulae, spinulae and premandibles absent.
Large, study and multi-toothed (8), outside of dominant apical tooth are 3 ‘outer’ teeth, the middle one longest; inner teeth 4, shorter posteriorly. Pecten mandibularis absent. Seta subdentalis clearly dorsal, simple/lanceolate, extending to near apical tooth. Seta interna may be represented on dorsolateral mandible by 4 long well sclerotised, sickle-shaped lamellae.
Well sclerotised, smoothly concave anterior margin; ventromentum with scale-like incisions (= not teeth of dorsomentum); dorsomental wall comprising 2 medially-separated bands of sclerotised teeth (dorsomental teeth).
Palp nearly as long as antenna, antenna-like, 3 segmented, with long basal segment, slender 2-segmented flagellum, and 2 large club-shaped sensory rods arising sub-basally on segment 2; without Ring Organ.
Anterior parapods fused basally, crowned with simple claws. Body surface smooth, with only well developed body setae. Posterior parapods well developed, with 2 strong setae basally. Procercus about 4x as wide as high, with 1 long subapical setae and 9 apical setae. Four anal tubules.
Distinguished from other Aphroteniinae by the smooth body, without tubercles, papillae or feathered setae. The antenna is 4-segmented and longer (=mandible length) in Paraphrotenia than other members of the subfamily. The head is uniquely long (>15% of body length) in Paraphrotenia.
Larvae are poorly known – description is based on only one from Patagonian Chile (South America), but the pupae are found in south-eastern Australian cool streams (where larvae have not been found).