Johannsen, 1905
Subgenus Orthocladius van der Wulp, 1974
Body
Medium sized larvae up to 9 mm long. Living larvae are greenish or brownish. The L4 setae are simpel and short. The anterior and posterior parapods are separate and bear rows of claws. Procercus and two pairs of anal tubules present (Wiederholm, 1983; Moller Pillot, 1984b).
Head
Pale head, 0.384 - 0.446 mm long (Schmid, 1993).
Antenna
The antenna consists of five segments. The blade is shorter than the flagellum and the antennal ratio is 1.45 - 1.80 (Schmid, 1993). Lauterborn organs are conspicuous.
Mentum
The mentum has one median tooth and 6 pairs of lateral teeth. The ventromental plates are weak and the setae submenti are placed close to the base of the ventromental plates. The beard is absent.
Labrum
The pecten epipharyngis consists of three scales, SI is bifid Orth frigidus labrum9 (Wiederholm, 1983; Moller Pillot, 1984b).
Mandible
The mandible has an apical tooth of normal length and 3 inner teeth (Wiederholm, 1983).
Differential characteristics
Orthocladius can be separated from all other genera, except Paratrichocladius, by the bifid SI, mentum with 1 median tooth and 6-9 pairs of lateral teeth, 5 segmented antenna (4 in O. consobrinus) and simpel body seta. Paratrichocladius however has a blueish thorax in freshly preserved larvae and a lobed ring beneath the ssd of the mandible. Both characters are absent in Orthocladius.
Orthocladius obumbratus can be separated from all other Orthocladius with pale head by:
5 segmented antenna, small and simpel L4, 6 pairs of lateral mental teeth, antenna ratio of 1.45 - 1.80 and setae submenti median to the base of the ventromental plates Or. wetterensis mentum.