Euconnus pseudotrimerus, Jałoszyński, 2022

Jałoszyński, Paweł, 2022, Taxonomy of ' Euconnus complex'. Part XXIV. Intermediate forms between Psomophus, Eupentarius and Euconnus s. str. in the East Palaearctic fauna unify problematic subgenera (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5194 (3), pp. 343-391 : 358-359

4. Euconnus pseudotrimerus species group

This group of two Japanese species described below (several more are known to me from females only) is characterized by a tiny (around 1 mm) and slender body form, round head, subconical pronota, indistinctly tetramerous (pseudotetramerous or pseudotrimerous, depending on interpretation), loosely assembled antennal clubs, and the aedeagi that resemble copulatory organs of the European species previously placed in the subgenus Napochus Thomson , i.e. drop-shaped, with distinct ventral and dorsal apical plates, of which the dorsal one is longer, and with symmetrical endophalli and paired small subapical projections situated near distal region of the ventral apical plate.

Before Napochus was placed as a junior synonym of Euconnus s. str. ( Jałoszyński 2021a), these two species (described below as E. pseudotrimerus and E. urauchianus ) could be described as highly similar to Napochus , but with one problematic feature ‒ the not exactly tetramerous antennal club. In E. pseudotrimerus the antennomere 8 is distinctly enlarged in relation to 7, but much smaller than 9, so the tetramerous club is not sharply delimited, as it is in the European species such as E. claviger ( Müller & Kunze, 1822) or E. pragensis ( Machulka, 1923) (see Jałoszyński 2021a). In E. urauchianus the club is even more problematic, as it appears trimerous (while the body form is similar to that of E. pseudotrimerus ). However, the antennomere 8 is slightly enlarged compared to 7, and therefore can be included in the club. See also Discussion.