Kieffer, 1922
Body
Small to medium sized larvae up to 8 mm long. Living larvae can be white green, blue or purple. The body with stout setae about half the segment long Tvet discoloripes body setae. The laterals in pairs. The anterior and posterior parapods are separate and bear rows of claws. Procercus well sclerotized and two pairs of anal tubules present Tvet discoloripes anal segm (Wiederholm, 1983; Moller Pillot, 1984b).
Head
The head length is up to 0.6 mm (Moller Pillot, 1984b).
Antenna
The antenna consists of five segments. The blade is subequal to the flagellum. Lauterborn organs are conspicuous.
Mentum
The mentum has one or two median teeth and 5 pairs of lateral teeth. The mentum has alternating lighter and darker longitudinal bands due to changing thickness of the chitin. The ventromental plates are weak. The beard is absent Tvet discoloripes mentum.
Labrum
The pecten epipharyngis consists of three scales, SI is branched to plumose and the premandible has one apical tooth (Wiederholm, 1983; Moller Pillot, 1984b).
Mandible
The mandible has an apical tooth and 5 pairs of inner teeth Tvet calvescens mandible. The seta interna has smooth or serrate branches. The mola has 2-3 simpel spines (Wiederholm, 1983).
Differential characteristics
Tvetenia can be identified by the stout body setae Tvet discoloripes body setae, mentum with 5 pairs of lateral teeth Tvet discoloripes mentum, weak ventromental plates and SI plumose. Tvetenia differs from Eukiefferiella by having long stout body setae.
Diversity
European species: 5
Treated species:
Tvetenia bavarica
Tvetenia calvescens
Tvetenia discoloripes
Tvetenia sp. a
Tvetenia verralli