Euconnus (Euconnus) fustiger
Creators: name: Jałoszyński, Paweł
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Euconnus
Euconnus fustiger

description: Euconnus (Euconnus) fustiger (Sharp)
Scydmaenus fustiger Sharp, 1874: 128. Redescribed by Hoshina, 2019b: 97.
Euconnus (Euconophron) fustiger (Sharp); Franz, 1975: 55.
Euconnus (Eupentarius) fustiger (Sharp); Jałoszyński, 2021a: 156, implied, by placing Euconophron as junior synonym of Eupentarius.
Euconnus Lewisii Sharp, 1886: 47. Placed as junior synonym of E. fustiger by Hoshina, 2019b: 97.
Euconnus (Euconnus) Lewisii Sharp; Csiki, 1919: 50.
Euconnus (Napochus) lewisii (Sharp); Hoshina, 2004a: 21; back to Euconnus s. str. in Jałoszyński, 2021b: 268 (implied, by placing Napochus as junior synonym of Euconnus s. str.).
Euconnus (Euconophron) miyawakianus Franz, 1976: 56. Synonymized with E. lewisii by Hoshina, 2004a: 21.
Euconnus (Euconophron) miyawakainus, misspelling in Hoshina, 2019b: 97.
Euconnus Schönfeldti Reitter, 1891: 19; syn. n.
(Figs 9–49)
Type material studied. Holotype of Scydmaenus fustiger Sharp: sex unknown (probably ♀) (Fig. 9), three labels (Fig. 10): “ Japan. / G. Lewis. / 1910-320.” [white with horizontal orange line, printed], “ Scydmaenus / fustiger / Type. D.S.” [white with black frame, handwritten and printed], “Type / H.T.” [circular label with red margin, printed] (NHM). Lectotype of Euconnus lewisii Sharp (here designated): ♂ (Fig. 13), mounted on thick cardboard (Fg. 14) with annotation: “ Euconnus / lewisius / D.S. / Nagasaki / 8.4.91 {below crossed out 9.... illegible} / Lewis”, and two labels (Fig. 14) “Sharp Coll. / 1905-313.” [darkened white, printed], circular label “Syn- / type” [white with blue margins, printed] (NHM). Paralectotypes of Euconnus lewisii Sharp (3 exx): ♀ (Fig. 11), mounted in the same way as lectotype, on thick cardboard (Fig. 12) with annotation: “ Euconnus / lewisius Type / D.S. / Nagasaki / 8.4.91. Lewis ”, and three labels (Fig. 12) “Sharp Coll. / 1905-313.” [darkened white, printed], circular label “Type / H.T.” [white with red margin, printed], and circular label “Syn- / type” [white with blue margins, printed] (NHM); ♀, mounted on a thick cardboard narrower than that for lectotype male, annotated: “ Euconnus / lewisius / var. / Nagasaki / 9.4.91 {“9” in “91” upside down, appearing as “6”}, and two labels “Sharp Coll. / 1905-313.” [darkened white, printed], circular label “Syn- / type” [white with blue margins, printed] (NHM); 1 ex. of unknown sex (abdomen destroyed, but no genital preparation attached), mounted on modern card, with four labels: “ Euconnus / lewisius” [white, handwritten], circular label “Syn- / type” [white with blue margins, printed], “ Nagasaki / 13.II.- 21.IV.81” [white, printed], and “ Japan. / G. Lewis. / 1910-320.” [white with horizontal orange line, printed] (NHM). Holotype of Euconnus miyawakianus Franz: ♂ (Fig. 19), four labels (Fig. 20), “ Japan 1974 / lg.H.FRANZ” [whte, printed], “ Mt.Kasuga b. / Nara, Honshu ” [white, printed], “ Euconnus / (Euconophron) / miyawakianus” / ♂ det. H.Franz m.” [white, handwritten and printed], “ Typus ” [red, handwritten] (NHMW). Paratype of Euconnus miyawakianus Franz: ♀, same data as for holotype, except for red label “ Allotypus ” (NHMW). Lectotype of Euconnus schoenfeldti Reitter (here designated): ♂ (Fig. 25), three labels (Fig. 26), “ Euconnus / Schönfeldti m. / Japonia 1890” [darkened white, handwritten], “Typus 1891. / E. Schönfeldti / Reitt. / Coll. Reitter ” [white with red frame, printed and handwritten], and “ Japán ” [white, printed] (HNHM).
Additional material studied (123 exx): HONSHU: Aichi Pref.: 4 exx, Misawa-chô, Seto City, 10.07.1999, T. Mizusawa leg. (cPJ); Chiba Pref.: 2 exx., Okuno, Ichihara City, 16– 18.04.2001, T. Shimada & S. Hatsushiba leg. (cPJ); Fukushima Pref.: 1 ex., Hibara, Kitashiobara V., 26.10.2003, T. Watanabe leg. (cPJ); 1 ex., Koishigahama, Aizuwakamatsu City, 30.05– 01.06.1999, T. Shimada leg. (cPJ); Gunma Pref.: 3 exx, Hôshi Spa, Niiharu-mura, 600 m, 20.10.2001, P. Jałoszyński leg. (cPJ); 1 ex., Akaya-goe, Minakami-machi, 550 m, 20.10.2001, P. Jałoszyński leg. (cPJ); 1 ex., Mt. Asamakakure-yama, 1450 m, Kurabuchi vill., 11.10.2002, S. Arai leg. (cPJ); Hiroshima Pref.: 9 exx., near Mitaka Dam, Nishinômi-jima, 25.08.2002, S. Arai leg. (cPJ); 2 exx., Mt. Hôdai-yama, 400 m, Nishinômijima, 25.08.2002, S. Arai leg. (cPJ); 1 ex., Miyama-no-taki, 240 m, Kure City, 22– 23.08.2002, S. Arai leg. (cPJ); Hyôgo Pref.: 5 exx, Miki City, Shizimi-machi, 19.03.2002, S. Nagashima leg. (cPJ); Ibaraki Pref.: 4 exx., Mt. Tsukuba, 500–700 m, 02.12.2001, P. Jałoszyński leg. (cPJ); 1 ex., same data but 08.06.2002 (cPJ); 1 ex., same data but 14.10.2002 (cPJ); 1 ex., same data but 19.07.2003 (cPJ); 2 exx., same data but 20.07.2003 (cPJ); 1 ex. same data but 03.06.2006 (cPJ); 2 exx, Mt. Tsukuba, foot of the mountain, 03.04.2004, P. Jałoszyński leg. (cPJ); 1 ex., Mt. Tsukuba, 50–100 m, SE slope, along stream in bamboo- Cryptomeria forest with Alnus trees, 06.04.2001, leg. P. Jałoszyński (cPJ); 1 ex, same data but 23.04.2002 (cPJ); 1 ex., Mt. Tsukuba, 50–100 m, 07.04.2001, P. Jałoszyński leg. (cPJ); 1 ex. same data but 05.04.2002 (cPJ); 5 exx, same data but 02.11.2002 (cPJ); 1 ex., hill near Mt. Tsukuba, bamboo forest at low alt., 29.09.2001, leg. P. Jałoszyński (cPJ); 2 exx, same data but 06.10.2001 (cPJ); 1 ex., same data but 11.10.2001 (cPJ); 1 ex., same data but 11.2001 (cPJ); 1 ex., same data but 13.11.2001 (cPJ); 3 exx, same data but 13.01.2002 (cPJ); 1 ex., same data but 19.01.2002 (cPJ); 3 exx, same data but 06.07.2002 (cPJ); 1 ex., Tsukuba City env., 04.2007, leg. P. Jałoszyński (cPJ); 3 exx., suburbs of Tsukuba City, bamboo- Cryptomeria forest, 10.11.2001, leg. P. Jałoszyński (cPJ); 1 ex., Shishitsuka ad Tsuchiura, lowland degenerated forest, 14.09.2002, leg. P. Jałoszyński (cPJ); Kanagawa Pref.: 3 exx., Mt. Takamatsu-yama, Atsugi City, 11.04.2001, H. Mizushima leg. (cPJ); 1 ex., Sagamiko env., 25.05.2002, leg. P. Jałoszyński (cPJ); 1 ex., same data but 14.07.2002 (cPJ); 1 ex., same data but 05.10.2002 (cPJ); 1 ex., same data but 01.11.2003 (cPJ); 4 exx. same data but 19.04.2003 (cPJ); 1 ex., Manazuru Penins., 04.11.2006, leg. P. Jałoszyński (cPJ); 6 exx. Yokosuka-shi, Oppama-chô, 11.08.1998, T. Mizusawa leg. (cPJ); 9 exx., same data but 12.01.1999 (cPJ); 2 exx, Kamakura, hills around city, 09.03.2002, leg. P. Jałoszyński (cPJ); 1 ex., Zigoku-sawa, Mt. Koma-yama, Ohiso town, 06.-5.2002, S. Arai leg. (cPJ); Nara Pref.: 1 ex., Mt. Obako-dake, 1300 m, near Nosegawa-mura, 26.03.2006, P. Jałoszyński leg. (cPJ); Saitama Pref.: 3 exx, Mt. Ryogami-san, Kiyotaki-goya, 1300 m, date unknown, T. Shimada leg. (cPJ); 1 ex., Shiga, Ranzan, 18.11.2002, K. Toyoda leg. (cPJ); 1ex., Mt. Shioyama, Ranzan, 17.06.2000, K. Toyoda leg. (cPJ); 1 ex., Marugami-no-taki, Ryougami-mura, 01.08.1999, S. Arai leg. (cPJ); 1 ex., Kasuga-jinja, Tamagawa vil., 02.10.1999, K. Toyoda leg. (cPJ); 1 ex., Mt. Arima-yama, Naguri vill., 1200 m, 08.05.2004, S. Arai leg. (cPJ); Tochigi Pref.: 2 exx. Nikko City env., 23.09.2006, leg. P. Jałoszyński (cPJ); Tokyo Pref.: 2 exx., Nippara Valley near Okutama, 03.08.2003, leg. P. Jałoszyński (cPJ); Yamagata Pref.: 1 ex., Mt. Haguro, broad-leaved primary forest, 19.09.2010, T. Lackner leg. (cPH); KYUSHU: Kagoshima Pref.: 1 ex., Ohsumi Lake, Kanoya City, Ohsumi Pen., 24.08.2001, S. Arai leg. (cPJ); 1 ex., Kirishima-jingu, 450 m, Makizono town, 27.08.2001, S. Arai leg. (cPJ); SHIKOKU: Ehime Pref.: 1 ex., Saragamine, Toon-shi, 100-years old dec. mountain forest, 16.05.2018, leg. P. Jałoszyński (cPJ); Kagawa Pref.: 2 exx., Nagara-dam, Ayakami-chô, 05.05.2003, S. Nagashima leg. (cPJ). Additionally, specimens from Saga Pref. (Kyushu) were also seen (NSMT).
Emended diagnosis. Body middle-sized (BL ~ 1.3–1.6 mm), thick bristles distributed on tempora and sides of pronotum; antennal club tetramerous, sharply delimited from compactly assembled proximal portion of funicle; vertex bulging posterodorsad, with rounded posterior margin; tempora in dorsal view much longer than eyes; pronotum subconical, broadest shortly in front of base, with weakly rounded sides strongly converging anterad; anterior pronotal margin much shorter than posterior margin; pronotum with two pairs of variously distinct small antebasal pits, lacking transverse groove, with sublateral carinae barely discernible or lacking; elytra densely setose; male legs and abdomen unmodified; aedeagus in lateral view with apical projections directed dorsad or distodorsad, thin-walled and stout median lobe, and endophallic structures situated in distal half of median lobe, darkly sclerotized, symmetrical, with lateral pair of strongly elongate structures forming a broad letter “V” in ventral view.
Redescription. Body of male (Figs 13, 19, 25, 31) moderately slender, strongly convex, BL 1.33–1.53 mm; cuticle glossy, pigmentation variable, from light to very dark brown, vestiture of setae lighter than cuticle.
Head rhomboidal, distinctly elongate and broadest at eyes, HL 0.30–0.35 mm, HW 0.25–0.30 mm; tempora in dorsal view about three 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 and posterior margin of vertex 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 0.50–0.58 mm; antennomeres 1 and 2 each elongate, 3–6 each about as long as broad or indistinctly elongate, 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, about as long as broad.
Pronotum subconical with weakly rounded sides, broadest just in front of base, PL 0.33–0.38 mm, PW 0.33–0.38 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 showing some variability among studied specimens, with a tendency toward reduction (all pits can be barely discernible or distinct, and inner or outer pair may be barely discernible), transverse groove lacking, sublateral carinae indistinct or lacking. Disc dorsally covered with fine, inconspicuous punctures and moderately dense thin suberect setae, sides with dense thick bristles that obscure the shape of pronotum.
Elytra oval, broadest slightly in front of middle, EL 0.70–0.80 mm, EW 0.53–0.63 mm, EI 1.21–1.37; 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 long, functional.
Legs moderately long and slender, unmodified.
Abdomen unmodified.
Aedeagus (Figs 15–18, 21–24, 27–30, 32–48) stout, AeL 0.15–0.25 mm; median lobe thin-walled and extremely prone to distortions during preparation, in ventral view broadest in sub-basal region, ventral apical plate lacking distal projection; distolateral regions of median lobe in ventral view variable, from rounded and inconspicuous to forming a pair of variously shaped, elongate lobes projecting distad and bearing tiny setae (in many studied specimens setae were broken off during preparation and only setal sockets could be recognized), in lateral view distal region of median lobe forming variously shaped, often fin-like distodorsal projection; endophallic structures symmetrical in intact aedeagi, but preparation may cause various displacements and endophallus may appear slightly asymmetrical; constant structures are a pair of long lateral sclerites forming a letter “V”, these are in fact composed of two elongate structures each, and one pair may be displaced toward middle of median lobe (as in Fig. 36), also median subapical subconical structure is constant, but it can rotate and in ventral view appears as a highly variable elongate or circular object, and in some cases is indiscernible; entire endophallus can be everted (also artificially, during preparation) so that median lobe becomes easily distorted and its distal region flips ventrad (as in Fig. 22). Parameres slender and short, not reaching apex of median lobe, in lateral view strongly bent and each with one apical seta. See also remarks on genital variability below.
Female. Externally slightly stouter than male, but otherwise indistinguishable. All females dissected during the present study are wingless. BL 1.31–1.58 mm; HL 0.31–0.35 mm, HW 0.25–0.30 mm, AnL 0.48–0.60 mm; PL 0.33–0.38 mm, PW 0.33–0.38 mm; EL 0.68–0.83 mm, EW 0.53–0.68 mm, EI 1.16–1.33.
Distribution. Japan: Honshu, Kyushu, Shikoku.
Remarks. Hoshina (2019b) redescribed this species and in the “Specimens examined” section listed: “ Holotype of Scydmaenus fustiger, ♂, Nagasaki (preserved in Natural History Museum, London (...) Syntypes of Euconnus lewisii, 2♂♂, Nagasaki”. The holotype of Scydmaenus fustiger preserved at NHM is a specimen of unknown sex, which has been dissected in the past (by Hoshina?), and the abdomen has been damaged. The specimen is not accompanied by any genital preparation. Its stout elytra suggest that it may in fact be a female, as it is similar to females included in the type series of E. lewisii (compare Fig. 9 and 11), but this is not possible to prove by any existing evidence. As for the syntypes of E. lewisii, at NHM there are four specimens: 2 females; one specimen that has been remounted and at least an attempt at dissection has been made, judging from a condition of the abdomen, but this specimen is not accompanied by a genital preparation; and one male (designated here as lectotype; Figs 13‒ 18) with a genital preparation attached. The aedeagus of the latter is illustrated in the present paper (Figs 15‒18), and it differs in some details from the one illustrated by Hoshina (2019b: figs 3‒5) for E. fustiger. However, I do agree with Hoshina (2019b) that E. fustiger is a senior synonym of E. lewisii, as there are no external differences that could be used to distinguish the holotype of E. fustiger and the syntypes of E. lewisii. I also agree with Hoshina (2004a) that E. miyawakianus Franz is identical with E. lewisii and E. fustiger, as I have not found any external characters to justify a separate position of E. miyawakianus. Interestingly, Franz (1976: fig. 5) illustrated the aedeagus of E. miyawakianus as strikingly different from what is illustrated here (Figs 21‒24), based on the same male holotype (the only paratype is a female). It seems that Franz’s illustration was based on the aedeagus oriented in euparal not ventrally or dorsally up, but rotated in such a way that the apical region was directed more towards observer. Remounting from euparal into Canada balsam might have also distorted the aedeagus. However, shapes of ventral and dorsal apical regions and endophallic structures in E. fustiger are highly variable and those in the type specimens of E. lewisii and E. miyawakianus fall within this variability.
Euconnus schoenfeldti Reitter, whose lectotype male is here illustrated (Figs 25‒30) for the first time, does not differ from E. fustiger in any features, including the aedeagus, and this name is placed as one more junior synonym of E. fustiger.
All studied type specimens of E. fustiger, E. lewisii, E. miyawakianus, and E. schoenfeldti have similar body lengths, ranging from 1.40 to 1.50 mm. Over 120 additional specimens from all over Japanese mainland (collected in 17 prefectures) were examined during the present study and results confirm that E. fustiger is a broadly distributed species, with a relatively narrow range of body length (extremely small specimens measure 1.31 mm, and the largest ones 1.58 mm). The studied specimens show some variability in pigmentation (from light to dark brown), and in proportions of body parts. For instance, the elytral index among males can be as low as 1.21 or as high as 1.37, and among females 1.16‒1.33. Moreover, the two pairs of antebasal pronotal pits are highly variable. In most specimens, all four pits are discernible, although they can be equally distinct, equally indistinct, or the outer or inner pair nearly obliterated. In a few specimens all antebasal pits are so minute that barely discernible under 100× magnification of stereomicroscope and in such cases the pronotum is virtually devoid of any antebasal sculpture. The most unusual, however, is variability found in the structures of the aedeagus (examples are shown in Figs 32‒49). The aedeagus in this species group is extremely thin-walled, and therefore prone to distortion during preparation. The distal sclerotized region in erected or semi-erected aedeagus is flipped distoventrad (see Fig. 22), and when the aedeagus is fully erected the endophallus is everted through the ostium, and then usually also the median lobe is distorted (narrowed or swollen). This condition causes the endophallic sclerites to displace in such a way that it is not possible to make sure that an erected aedeagus is identical with one preserved in a resting position. Maceration in KOH or NaOH strongly promotes artificial erection and may lead to obtaining preparations of variously erected aedeagi, which look so different that several distinct species can be erroneously identified in a sample collected in the same spot. Among specimens examined during the present study, I found variability (true variability, and not caused by inappropriate preparation method) in: (1) the shape of the lateral distal region of the median lobe, which can form distinct, projecting lobes, differing in shape and size in various specimens; (2) shape of the dorsal apical region in lateral view; (3) shape and arrangement of endophallic structures; and (4) shape of dorsal apical plate. The lateral elongate, darkly sclerotized endophallic structures (visible e.g., in Fig. 32) are in fact composed of two pairs of elongate sclerites, which in resting position overlap and appear as one pair. However, the narrower and usually more basally and mesally situated pair of sclerites can move mesad and become clearly discernible (as in Fig. 36). This may appear as a species-specific difference, which it is not. Moreover, the thick median subconical structure with truncate apex (well-visible in Fig. 36 in subapical region, presumably functioning as a distal flagellar armature with the true gonopore) is integrated with the movable endophallus and any rotation inside the median lobe changes remarkably the shape of this element in ventral view, from elongate and distinct (Fig. 36) to entirely indiscernible (e.g., Fig 38), and intermediary states can also be found (e.g., in Fig. 32 this median element is displaced close to middle of aedeagus and appears as a short, round sclerotization). Shapes of all structures strongly change with even slight rotations of the aedeagus in solid medium, which additionally complicates comparisons. I was not able to find any correlation of the observed variability with geographic factors, and often specimens collected from the same spot and externally indistinguishable show differences in genital structures. I conclude that E. fustiger is either a single species showing a great variability in male genital structures, or a complex of many local populations that still maintain a limited gene flow, and such populations have a potential to evolve into separate species if they become physically separated. This phenomenon requires comprehensive genetic studies.
Previously, this species was placed in the subgenera Euconophron Reitter, 1909 (currently a junior synonym of Eupentarius Reitter, 1907) (by Franz (1975, 1976)) or Napochus Thomson, 1859 (currently a junior synonym of Euconnus s. str.) (by Csiki (1919)). After redefining Euconophron /Eupentarius (Jałoszyński 2017b; d, 2021a; Vít 2005) and Euconnus s. str. (Jałoszyński 2021b), the placement of E. fustiger in Euconnus s. str. can be confirmed.
This is the commonest of mainland Japanese Euconnus (s. str.) species; it inhabits leaf litter in lowland and mountainous deciduous and mixed forests.
Efforts should be made to obtain non-distorted preparations (by avoiding maceration in alkali!), and descriptions of new species belonging to this complex should be supported by a profound understanding of geographical variation and character variability. I have seen many Japanese specimens of Euconnus which markedly differ in body length from E. fustiger (being either much smaller or much larger), showing the same form of aedeagus. Unfortunately, many such species have already been described (see comments in further parts of this paper), based on single or few specimens with strongly distorted aedeagi, which makes it impossible to unambiguously identify some (or all) of them. The taxonomy of the Japanese ‘ Euconnus fustiger group’ seems to have reached the level of chaos that makes future studies extremely difficult, if not impossible.
description: Published as part of 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), pp. 1-37 in Zootaxa 5093 (1) on pages 6-12, DOI: 10.11646/zootaxa.5093.1.1, http://zenodo.org/record/5901006