Belongs within: Euplectitae.
Trimium is a western Palaearctic genus of large-headed pselaphine beetles (Raffray 1903).
Characters (Raffray 1903): Head large, more or less truncated in front. Antennae 11-segmented, not very far apart at their insertion; tenth article in a transverse triangle, asymmetrical; last article very large, forming the club by itself. Last article of the palps always much larger than the preceding one. Prothorax almost orbicular, with a transverse groove. Shoulders entire, not toothed. Mesocoxae contiguous, processes of meso- and metasternum reduced to very thin blades hidden by coxae. Metacoxae contiguous.
<==Trimium Aubé 1833R03
|--T. ampliventre Baudi 1889R03
|--T. brenskei Reitter 1884R03
|--T. (Trimium) brevicorne (Reichenbach 1816)NT01 (see below for synonymy)
|--T. carpathicum Saulcy 1875R03
|--T. caucasicumR03
|--T. cavicolle Reitter 1880R03
|--T. diecki Reitter 1881R03
|--T. domogleti Reitter 1881R03
|--T. emonae Reitter 1881R03
|--T. expandum Reitter 1884R03
|--T. hopfgarteni Reitter 1881R03
|--T. imitatum Reitter 1881R03
|--T. koenigi Reitter 1887R03
|--T. latiusculum Reitter 1879R03
|--T. lenkoranum Reitter 1898R03
|--T. longipenne Reitter 1879R03
|--T. longiventre Raffray 1903R03
|--T. merkli Reitter 1894R03
|--T. minimum Dodero 1900R03
|--T. raffrayi Guillebeau 1890R03
`--T. zoufali Krauss 1900R03
Nomen nudum: Trimium abdominale Motschulsky 1851R04
Trimium (Trimium) brevicorne (Reichenbach 1816)NT01 [incl. T. brevipenne Chaudoir 1845R03, T. chevrieri Tournier 1867R03, T. discolor LeConte 1878NT01, Melba discolorR03, T. latipenne Tournier 1867R03, T. brevicorne var. puncticeps Reitter 1880R03]
*Type species of generic name indicated
References
[NT01] Newton, A. F., M. K. Thayer, J. S. Ashe & D. S. Chandler. 2001. Staphylinidae Latreille, 1802. In: Arnett, R. H., Jr & M. C. Thomas (eds) American Beetles vol. 1. Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia pp. 272–418. CRC Press: Boca Raton.
[R03] Raffray, A. 1903. Genera et catalogue des psélaphides. Annales de la Société Entomologique de France 72: 484–604.
[R04] Raffray, A. 1904. Genera et catalogue des psélaphides [part III]. Annales de la Société Entomologique de France 73: 401–476, pls 1–3.