Euconnus (Euconnus) raucus Sharp, 1886

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 : 20-22

Euconnus (Euconnus) raucus Sharp

Euconnus raucus Sharp, 1886 : Redescribed by Hoshina, 2019b: 99.

( Figs 70–71 )

Type material studied. Holotype: ♀ ( Fig. 70 ), mounted on thick card with annotation: “ Euconnus / raucus Type / D.S. / Nagasaki. / 26.3.81. Lewis.”, with two labels ( Fig. 71 ): “ Japan / G. Lewis. / 1910-320” [white with orange horizontal line, printed], and circular label “Type / H.T.” [white with red margin, printed] ( NHM).

Emended diagnosis. The only known female of this species matches diagnosis of E. fustiger , with exception of distinctly larger body: BL 1.75 mm. See Remarks.

Redescription. Body of female ( Fig. 70 ) moderately slender, strongly convex, BL 1.75 mm; cuticle glossy, pigmentation dark brown, vestiture of setae lighter than cuticle.

Head rhomboidal, distinctly elongate and broadest at eyes, HL 0.40 mm, HW 0.35 mm; tempora in dorsal view about 2.5 times as long as eyes and strongly converging posterad; vertex and frons confluent, weakly and evenly convex, posterior margin of vertex rounded, slightly bulging posterodorsad; supraantennal tubercles barely marked; frons between antennae steeply declining; clypeus unmodified. Eyes moderately large, finely faceted, distinctly but not strongly projecting laterad from the head silhouette, in lateral view oval. Punctures on vertex and frons inconspicuous, fine and sparse; setae short and sparse, suberect, tempora densely covered with thick bristles directed laterocaudad. Antennae moderately slender, with compact proximal portion of funicle and moderately loosely assembled, strongly broadened and sharply delimited tetramerous club, AnL 0.70 mm; antennomeres 1 and 2 each elongate, 3–6 each about as long as broad, 7 slightly narrower than 6, indistinctly elongate, 8 much broader than 7, slightly transverse, 9 and 10 each strongly transverse and indistinctly broader, but distinctly shorter than 8, 11 indistinctly narrower than 10, slightly transverse.

Pronotum subconical with weakly rounded sides, broadest at base, PL 0.45 mm, PW 0.48 mm; anterior margin nearly straight and much shorter than posterior margin, anterior corners weakly marked, sides of pronotum weakly, evenly rounded and strongly converging anterad; posterior corners distinctly obtuse-angled, well-marked; posterior margin nearly straight. Pronotal base with two lateral pairs of tiny and shallow pits, transverse groove and sublateral carinae lacking. Disc dorsally covered with fine, inconspicuous punctures and moderately dense thin suberect setae, sides with dense thick bristles.

Elytra oval, broadest distinctly in front of middle, EL 0.90 mm, EW 0.73 mm, EI 1.24; basal impressions short and shallow, humeral calli moderately strongly elevated, elongate, each delimited from adscutellar region by shallow elongate impression running posterolaterad, elytral apices separately rounded. Punctures on elytral disc fine, inconspicuous; setae long, moderately dense, suberect. Hind wings lacking.

Legs moderately long and slender, unmodified.

Abdomen unmodified.

Male. Unknown (see Remarks).

Distribution. Japan: Kyushu.

Remarks. This species was ‘redescribed’ by Hoshina (2019b). However, the single known type specimen preserved at NHM is a rather unremarkable female and it remains unknown how a male has been unambiguously assigned to this species. I have seen many similar specimens from Kyushu and Honshu, mostly from mountainous areas, matching the body length and form of the holotype female of E. raucus , but they represented several species whose males differ in genital structures. However, it is possible that these differences will turn out to be a morphocline, as seems to be the case for the smaller-bodied and broadly distributed E. fustiger . The female of E. raucus seems to differ from females of E. fustiger in a slightly stouter head and a shorter antennomere 11 (which is slightly transverse, whereas in most females of E. fustiger it is at least as long as broad). A larger sample of similarly large-bodied specimens from many localities is necessary to clarify the status of E. raucus .

If the Hoshina’s (2019b) identification is correct, then the aedeagus of E. raucus differs from that of E. fustiger in a long median, asymmetrical pointed endophallic sclerite with a subapical projection. However, this illustration of Hoshina also shows a genital organ distorted by improper preparation, with the endophallus partly extruded, which may in future make identifications based on non-distorted preparations difficult, if not impossible. Hoshina later described several extremely similar, large-bodied Euconnus species with similar (and often also distorted) aedeagi. I found it impossible to clarify whether these are distinct species or some are identical with E. raucus , or what actually E. raucus is (i.e., whether it is a distinct species or the holotype female is only an unusually large specimen of the variable E. fustiger ). None of the large-bodied, E. fustiger -like species in my collection match the aedeagal structures illustrated by Hoshina for ‘ E. raucus ’ and his other similar species, suggesting that this species complex is large and taxonomically challenging. The current situation caused by carelessly describing new species based on distorted aedeagi may already pose problems impossible to solve by morphological study.

Euconnus raucus is here placed in Euconnus (s. str.), based on the tetramerous antennal club, the pronotum bellshaped, broadest behind middle, and lack of the median antebasal pronotal pit.

Figures

FIGURES 70–71. Euconnus raucus, female. Dorsal habitus (70) and annotated mounting card with historical labels (71) of holotype.