Euconnus (Euconnus) kumejimensis Hoshina, 2013

Jałoszyński, Paweł, 2022, Euconnus Thomson of Japan: redescriptions of species established by Reitter, Sharp and Franz, new synonyms, and summary of current state of knowledge (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5093 (1), pp. 1-37 : 25-26

Euconnus (Euconnus) kumejimensis Hoshina

Euconnus (Euconophron) kumejimensis Hoshina, 2013: 285 . Aedeagus also illustrated in Hoshina, 2019a: figs 10‒12. Euconnus (Eupentarius) kumejimensis Hoshina ; Jałoszyński, 2021a: 156, implied, by placing Euconophron as junior synonym of Eupentarius.

Euconnus (Euconnus) kumejimensis Hoshina ; here placed in Euconnus s. str.

Remarks. This species is known to occur on Kumejima, a small island near Okinawa-jima, the main island of the Ryukyu Archipelago. It belongs to the Euconnus alesi species group, which is broadly distributed throughout entire Ryukyuan Arch, from Koshikishima rettô near the western cost of Kyushu to Yonaguni-jima in the south, and E. alesi Vít, 2011 is known to occur in the Chinese province of Fujian. This strongly suggests that similar species should be also expected to occur in Taiwan. All these beetles share similar body form, conspicuous modifications of the head in males (a transverse glandular groove or impression that dorsally demarcates a slightly bulging median frontal region), distinctly tetramerous antennal clubs, and aedeagal structures. There are differences between samples from different islands of the Ryukyus that I have examined, including the shape of the male cephalic glandular structure and the aedeagus. However, there also seems to be some variability within populations inhabiting large islands. The taxonomic situation is complicated by several factors: (1) the aedeagus in this group, similarly as that in the E. fustiger group, is thin-walled and highly prone to distortions during preparation; (2) the aedeagus of E. alesi was illustrated based on a slightly damaged specimen, with the median lobe cracked and lacking parameres; (3) the aedeagus of the unique male included in the type series of E. kumejimensis is fully erected, which means that the entire endophallus is everted outside the median lobe, with its sclerotized structures displaced, and the ventral apical plate is flipped ventrad to open the ostium; and (4) another member of this group, E. touko , was described from Shimokoshiki Island and although its illustrated aedeagus is intact, it is impossible to compare it with the one illustrated for E. kumejimensis . Moreover, Hoshina (2013) stated that “both parameres of aedeagus bent at a right {angle} in lateral view”, but in fact in the aedeagus illustrated in the lateral view in his fig. 5, the structure that appears as a paramere is a hybrid of a paramere (proximal half) with the dorsal apical plate, which gives an impression of a slender ‘paramere’ bent at a right angle. As illustrated in figures 3‒4 in the same study, the parameres are short and do not reach the apex of median lobe. Hoshina (2019a) illustrated again an aedeagus supposedly belonging to E. kumejimensis , but he did not explain where this male specimen came from. The aedeagus shown in that paper in ventral and dorsal views seems almost intact (but almost certainly highly simplified), whereas that in the lateral view is fully erected. These illustrations can hardly be compared with those in the original description, and may or may not show the same species. This only adds uncertainty regarding the taxonomy of the E. alesi species complex.

Fortunately, Kumejima, where the male holotype of E. kumejimensis comes from, is a small island with the longest diameter ~ 12‒13 km and a rather limited forested area suitable for leaf-litter Scydmaeninae . It should be possible to collect new material and properly redescribe this interesting species, which is a prerequisite to analyze populations from other islands of the Ryukyus, possibly Taiwan, and the Chinese coast in Fujian. At the moment taxonomic treatment of this group is not possible, despite an interesting sample of specimens from various Ryukyuan islands that I have examined (and have not been able to identify to species level).

Vít (2011) placed E.alesi in Euconophron , and also Hoshina (2013) placed E. kumejimensis in the same subgenus. However, as redefined by Jałoszyński (2017b, d; 2021a), Eupentarius (a senior synonym of Euconophron ) has a median antebasal pronotal pit and a clearly bifurcate or deeply emarginate aedeagal apex, features that these two Far Eastern species lack. Their placement is here corrected to Euconnus (s. str.).