Ctenisomorphus yinggelingensis, Li & Wang & Yin, 2021

Li, Qi-Qi, Wang, Yan & Yin, Zi-Wei, 2021, First species of Ctenisomorphus Raffray, 1890 from China, with comments on Largeyeus J. - K. Li, 1993 (Coleoptera, Staphylinidae, Pselaphinae), Zootaxa 5016 (4), pp. 588-596 : 589-593

Ctenisomorphus yinggelingensis sp. nov.

( Figs 1 , 2 )

Type material (6 exx.). HOLOTYPE: CHINA: ♂ , ‘ China: Hainan, Baisha Co., Budao Vill., Yinggeling , 19°03'00"N, 109°23'21"E, 285~ 365 m, 19.iv.2018, mixed leaf litter, sifted, Jiang Ri-Xin leg. (布łh,NJ哥岭)’ ( SNUC) . PARATYPES: CHINA: 1 ♂, 4 ♀♀, same label data as holotype ( SNUC) .

Diagnosis. Male. Body length approximately 2.0 mm. Maxillary palpomeres 3 and 4 with lateral extensions shorter than their respective mesal parts. Antennomers 3 slightly elongate, 4 as long as broad, antennomeres 8 2.2– 2.3 times as long as antennomeres 9. Elytra with discal striae extending from outer basal foveae to approximately apical 4/5 of elytral length. Aedeagus with median lobe almost symmetric dorso-ventrally; endophallus composed of elongate cluster of small spines; parameres short and roundly triangular, each with two apical setae. Female. Body length approximately 2.1–2.2 mm, antennomeres 2–7 each more or less elongate, 8 as long as broad, 9–11 elongate, gradually becoming longer and broader.

Description. [a female specimen was disarticulated to check the foveal pattern] Male. Body ( Fig. 1A ) length 1.97–2.03 mm; color reddish-brown, tarsi and mouthparts lighter. Postantennal areas, basolateral areas of head, base of pronotum, posterior margin of elytra and tergite 1 (IV), and bases of tergite 1 and sternites 2 (IV) and 3 (V) covered with broad squamous setae, other parts of the body usually with spatulate setae.

Head ( Fig. 2A ) rounded at base, slightly broader than long, length from anterior margin of frontal rostrum to head base 0.36 mm, width across eyes 0.41 mm; apical portion of frons sharply sloping, almost vertical to plane of vertex, anterior margins of frons and clypeus each distinctly carinate and elevated. Eyes greatly prominent, each composed of approximately 40 moderately large facets. With C-shaped setose sulcus anterior to each eye. Venter with small gular foveae (posterior tentorial pits) in oval opening, lacking median carina. Maxillary palpus ( Fig. 2B ) with palpomeres 2–4 greatly extended laterally, each with coalesced setae at apex of extension; palpomere 1 minute, palpomere 2 pedunculate for basal half, apical half broadened, palpomere 3 broad, subtriangular, jointed with palpomere 4 at mesal margin of latter segment, palpomere 4 elongate, broadest bat basal 1/3. Antennae 1.45–1.46 mm long (antennomeres 3–11 sexually dimorphic), male antennomeres as follow: 1 thick, subcylindrical, 2 much shorter and slightly narrower than 1, 3 ( Fig. 2C ) slightly elongate, 4–7 of similar width, successively shorter, 4 approximately as long as broad, 5–7 each transverse, club formed by apical 4 antennomeres ( Fig. 2D ), 8 greatly elongate, slightly curved, approximately 2.2–2.3 times as long as 9, 9 approximately as broad as 8, 10 obliquely narrowed at base, much longer than 9, 11 longer than 10, with truncate base and round, narrowed apex.

Pronotum ( Fig. 2A ) slightly longer than wide, length along midline 0.39–0.41 mm, maximum width 0.37 mm, widest at basal 1/3, sides rounded; disc slightly convex, glabrous, with small median antebasal fovea covered by squamous setae, lacking lateral antebasal foveae. Prosternum with anterior part slightly longer than coxal part, with small lateral procoxal foveae; margins of coxal cavities weakly carinate.

Elytra much broader than long, length along suture 0.59–0.60 mm, maximum width 0.74 mm; each elytron ( Fig. 2E ) with two large, setose basal foveae, lacking subbasal fovea; humeri slightly prominent but not denticulate; sutural stria broad and deep, thin discal stria extending from outer basal foveae to approximately apical 4/5 of elytral length; with broad posterolateral cleft.

Mesoventrite short, confluent with metaventrite, with broad and setose subbasal sulcus separated by thick ridge at middle, with single setose median mesoventral fovea at posterior end of ridge, lacking lateral mesoventral foveae. Metaventrite broadly impressed along middle, with large, setose median metaventral and lateral mesocoxal foveae; posterior margin with deep split at middle.

Legs elongate, lacking modifications.

Abdomen slightly narrower than elytra, widest at lateral margins of tergite 1 (IV), length of abdomen along midline 0.54–0.59 mm, maximum width 0.71 mm, with long segments IV and V and short VI–VIII. Tergite 1 (IV) slightly shorter than tergite 2 (V) along middle, tergites 1 and 2 each with broad, setose basal sulcus, tergite 3–5 (VI–VIII) successively shorter, tergites 1–4 (IV–VII) each with accompanying paratergites, 1–5 (IV–VIII) each with one pair of basolateral foveae. Sternite 2 (IV) and 3 (V) with broad, setose basal sulcus, sternite 2 (IV) with large basolateral sockets, sternites 3–5 (V–VII) each with one pair of basolateral foveae.

Aedeagus ( Fig. 2F–H ) 0.17 mm long, median lobe dorsoventrally almost symmetric, apical portion greatly bent ventrally, gradually narrowing apically to form round apex; endophallus composed of numerous small spine-like structures; parameres short, roundly triangular, each with two long setae at apex.

Female. Similar to male in external morphology; antennae shorter; each eye composed of approximately 33 facets. Measurements (as for male): body length 2.1–2.2 mm; length/width of head 0.35–0.36/ 0.41–0.42 mm, pronotum 0.40–0.41/ 0.37–0.38 mm, elytra 0.76–0.80/ 0.60–0.62 mm; abdomen 0.65–0.71/ 0.75–0.80 mm; antennae ( Fig. 1B ) lacking modifications, length 1.31–1.36 mm, antennomere 7 longer than 6 and 8, 8 shortest, 9–11 enlarged, forming clubs.

Comparative notes. Separation of members of Ctenisomorphus usually relies on the relative lengths (proportions) of the male antennomeres (especially antennomeres 8–11), the form of the maxillary palpi, as well as the configuration of the aedeagus. At present seven species of the genus have been known. The male of the new species is most close to that of C. coomani (Jeannel) distributed in Thailand, Vietnam and Myanmar by sharing a similar general appearance, and can be separated from the latter only by subtle differences: in the new species antennomeres 3 are slightly elongate, antennomeres 4 are approximately as broad as long, and antennomeres 8 are relatively shorter in relation to antennomeres 9, while both antennomeres 3 and 4 in C. coomani are transverse, and antennomeres 8 are relatively longer in relation to antennomeres 9. In addition the shape of the apical portion of the aedeagus, and the position and form of the endophallus of the new species are different from the illustration given in Jeannel (1957), when rotating to a same angle for comparison. Ctenisomorphus yinggelingensis sp. nov. can be separated from the other congeners except for C. heterocerus (Reitter) by the following characters:

― from C. fortipalpis Besuchet & Cuccodoro distributed in Iran, United Arab Emirates by the relatively much shorter maxillary palpomeres 3 and 4, and different structure of the endophallus;

― from C. garamanticus Peyerimhoff distributed in Algeria, and the Afrotropical region by the relatively much shorter antennae and legs, shorter antennomeres 9 in relation to antennomeres 8 (antennomeres 9 longer than half length of antennomeres 8 in C. garamanticus ), and transverse antennomeres 7 (elongate in C. garamanticus );

― from C. indicus (Jeannel) distributed in Uttar Pradesh, northern India by the transverse antennomeres 4–7 (about as long as wide in C. indicus );

― from C. lindbergi (Jeannel) distributed in Central Asia by the slightly elongate antennomeres 3 (transverse in C. lindbergi ), and antennomeres 10 being much shorter than 8 (about as long as 8 in C. lindbergi );

― from C. major (Raffray) distributed in the Middle East and Africa by the four-segmented antennal clubs and transverse antennomeres 5–7 ( C. major has two-segmented antennal clubs, and slightly elongate antennomeres 5–7).

Judging from the original description ( Reitter 1900), C. heterocerus of Uzbekistan is deemed to be a member of Ctenisomorphus , but its separation from the other members of the genus is based solely on its geographic isolation.

Distribution. China: Hainan.

Etymology. The species is named after Yinggeling Nature Reserve, type locality of the new species.

Figures

FIGURE 1. Habitus of Ctenisomorphus yinggelingensis sp. nov. A. Male. B. Female. Scale bars: 0.5 mm.

FIGURE 2. Diagnostic characters of Ctenisomorphus yinggelingensis sp. nov., male. A. Head, pronotum, and elytral base. B. Left maxillary palpus, in ventral view. C. Antennomeres 1–4. D. Antennomeres 7–11. E. Right elytron. F–H. Aedeagus, in dorsal (F), lateral (G), and ventral (H) view. Scale bars: 0.3 mm in A, D, E; 0.2 mm in C; 0.1 mm in B, F–H.