Subgenus Tetramelus Motschulsky

Tetramelus Motschulsky, 1869: 257. Type species: Scydmaenus oblongus Sturm, 1838 (des. by Franz in Newton & Franz (1998): 147).

Remarks. Morphological structures were illustrated and an emended diagnosis was given in Jałoszyński (2015c); further notes on character variability can be found in Jałoszyński (2017a, 2021a).

Tetramelus, as currently defined, can be identified using the following set of co-occurring characters: hypostomal ridges running posteromesally; head ventrally lacking deep narrow longitudinal groove connecting gular plate and submentum; pronotum lacking longitudinal hypomeral grooves; pronotum broadest in front of middle; antenna in male unmodified, gradually thickened or with variously distinct tetramerous club; and tarsomere 4 in all legs lacking long distoventral lobe (for key to subgenera see Jałoszyński (2022b)).

Distribution. Africa: Algeria, Cameroon, Comoros, Kenya, Lesotho, Madagascar, RSA, Swaziland, Tanzania; Asia: Asian Turkey, Nagorno-Karabakh, Nepal, “Syria”; Australia: Australia (incl. Franklin Is., Lord Howe Is., Reevesby Is., Tasmania); Caribbean: Jamaica; Europe: Albania, Andorra, Armenia, Austria, Belgium, Bosnia & Herzegovina, Bulgaria, Croatia, Czech Rep., France, Georgia, Germany, Greece, Hungary, Italy, Kosovo, Lithuania, Macedonia, Montenegro, Netherlands, Poland, Portugal, Romania, European Russia, Slovakia, Slovenia, Spain, Switzerland, European Turkey, Ukraine; North America: Canada, USA; Pacific: New Caledonia, New Zealand; South America: Bolivia, Brazil, Peru.

Composition. At the time of submission of the present study there were 233 species and 2 subspecies. However, in a parallel study on Malagasy species some Stenichnini are transferred into Tetramelus (Jałoszyński, in press), which results in 17 more species included in this subgenus.

All new Chinese species described below are microphthalmous, wingless and have reduced wing-related exoskeletal structures, including lack of humeral calli and the elytra strongly narrowing anteriorly; males have a large and deep median impression on the metaventrite, and all species except one have modified trochanters. All species are externally very similar, they differ in body size, pigmentation, modifications of male trochanters, and genital structures. The Chinese Tetramelus species are morphologically so close to their Western Palaearctic congeners that they can be included in the same Euconnus oblongus group (Jałoszyński 2021a).