(Staeger, 1839)
Body
Large larvae up to 12 mm long. Living larvae pink. Claws on the posterior parapods are simpel. No lateral and ventral tubules (Wiederholm, 1983; Moller Pillot, 1984a sub P. gr. vitiosus).
Head
Length 0.40 mm with 3 pairs of eyes Pach arc eyes (Moller Pillot, 1984a)
Antenna
The antenna consists of 5 segments. The basal segment is longer than the flagellum. Lauterborn organs distally on the second segment.
Mentum
The mentum has 2 median teeth Parach vitiosus mentum and 7 pairs of lateral teeth. The ventromental plates crenate anteriorly with striae radiating in all directions are 0.9 - 1.2 x as wide as the mentum.
Labrum
SI is simpel and labral lamellae are absent. The pecten epipharyngis with several rows of teeth. The premandible with 3 apical teeth Parach vitiosus premandible.
Mandible
The mandible with a small dorsal tooth, one long apical tooth and 2 inner teeth with seta subdentalis (SSD) present Parach vitiosus mandible 8 (Wiederholm, 1983; Moller Pillot, 1984a).
Differential characteristics
The species with one median mental tooth can be distinguished by the flat mentum and 7 pairs of lateral teeth. Parach arc mentum. The species with 2 median teeth can be separated by the 7 pairs of lateral teeth, flat mentum Parach vitiosus mentum and 2-4 teeth on the premandible Parach vitiosus premandible where Harnischia has 6 teeth.
P. biannulatus (as P. (gr) vitiosus in Wiederholm, 1983 and Moller Pillot, 1984a) can be separated from the other Parachironomus by the double median mental teeth and striae on the ventromental plates radiating in all directions.