Van der Wulp, 1874
Body
Medium sized larvae up to 8 mm long. Living larvae are often blueish or purplish. The anterior parapods are usually separate. The two posterior parapods bear rows of claws. Procercus is well developed and often with a posterior spur or uneven sclerotization. The setae on the procercus are short, only twice as long as the procercus. Supra-anal seta short and two pairs of anal tubules are present (Wiederholm, 1983; Moller Pillot, 1984b).
Head
The head is yellow or brown and the eyes are fused, egg-shaped and the individual eyes are difficult to distinguish Metr hirtic agg head lateral.
Antenna
The antenna consists of five segments. When the antenna is reduced the blade is longer than the flagellum Metr fuscipes antenna. When the antenna is normal, the fourth segment is longer than the third Metr hirtocollis agg antenna 8.
Mentum
The mentum has one Metr terrester mentum or two median teeth Metr fuscipes mentum and usually 5 pairs of lateral teeth. Sometimes with a very small accessory tooth. The ventromental plates are weak and the beard is absent.
Labrum
The pecten epipharyngis consists of three short scales, SI is plumose or simpel (M. fuscipes). Labral lamellae are present between the SI Metr hirticollis agg labrum. The premandible has 2-4 apical teeth (Wiederholm, 1983; Moller Pillot, 1984b).
Mandible
The mandible has an apical tooth and 4-5 inner teeth Metr terrester mandible. The seta interna has simpel or plumose branches (Wiederholm, 1983).
Differential characteristics
The eye of Metriocnemus is distinctive. The smaller and larger eyes are merged into eggschaped eye Metr hirtic agg head lateral. In all other genera the smaller eye can be distinguished from the larger eye Limnophyes head lateral. Metriocnemus can be separated from all genera except Thienemannia by the mentum with 5 pairs of lateral teeth and the weak ventromental plates Metr hirticollis agg mentum, antenna 5 segmented Metr hirtocollis agg antenna 8, plumose SI and labral lamellae present Metr hirticollis agg labrum, mandible with 4-5 teeth Metr terrester mandible. Metriocnemus can be separated from Thienemannia Thienemannia gracilis anal seg by the well developed sclerotized procercus and the short seta on the procercus Metr scirpi anal segments.
Diversity
European species: 17
Treated taxa:
Species-group Metriocnemus hygropetricus agg.
Species-group Metriocnemus hirticollis agg.
Species-group Metriocnemus terrester agg.
Metriocnemus fuscipes
Metriocnemus inopinatus
Metriocnemus martinii
Metriocnemus tristellus