Scolytus unicornis Cao, Petrov&Wang, 2023

Cao, Yufeng, Yu, Guangyu, Petrov, Alexander V., Li, You, Li, Ting, Tarno, Hagus, Cao, Guanghong, Xu, Ye & Wang, Jianguo, 2023, A new species of Scolytus Geoffroy (Coleoptera, Curculionidae, Scolytinae) from Yunnan, China, Zootaxa 5284 (1), pp. 185-191 : 186-189

Scolytus unicornis Cao, Petrov&Wang sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:925E89A6-E720-4A40-A381-6E803615FED4

Type material. Holotype, male, China. Yunnan Province, Jinghong City, Menghai County, Naban River Nature Reserve , Guomen Mountain , alt. 1000 m, N 22.25°, E 100.61°, from Ulmus sp. , 28 June 2022; Y. F. Cao. Holotype deposited in the National Zoological Museum of China, Institute of Zoology , Beijing, China .

Allotype: female, the same data as the holotype. Deposited in the National Zoological Museum of China, Institute of Zoology , Chinese Academy of Sciences , Beijing, China.

Paratypes (2 ♁, 3♀): the same collection data as the holotype. Paratypes were deposited in the Laboratory of Biologic Invasive of Jiangxi Agricultural University , Nanchang (1♁, 2♀); Kunming Institute of Zoology , Chinese Academy of Sciences, Kunming, China (1♁, 1♀) .

Diagnosis. ( Fig. 1 A–F ). The new species is closely related to S. squamosus Yin & Huang , but can be distinguished by its larger body size and the frontal tubercle of female. In previous records, the females of only two Palearctic species, S. major Stebbing and S. gretschkini Sokanovskiy , had a median frontal tubercle above the epistoma ( Mandelshtam & Petrov 2010; Petrov 2019). However, the ventrite 2 of S. unicornis has a large spine that can be clearly distinguished from the first two ( Petrov & Mandelshtam 2010).

Description. ( Fig. 1 A–F ). Male, total length 3.8–4.2 mm long (mean = 4.0; n = 3), 2.12 times as long as wide (paratypes 2.13). Head and pronotum black; antennae reddish brown; legs, elytra, and abdomen reddish brown to dark brown.

Head. Frons flat, surface shiny. Vertex fine, moderately dense punctures with a narrow, shallow, longitudinal gutter in the middle. Frons surface with smooth middle part having shallow punctures; space between punctures equal to four times that of the puncture diameter; lateral areas under the eyes with long bristle-like setae, apices of bristles incurved and directed towards middle of frons. Epistoma with deep longitudinally aciculate lines covered by sparse short yellow hairs; epistomal margin above mandibles strongly incurved towards central portion of the frons, with a pair of erect pointed brushes of dense setae. Antennal scape flattened, elongate, club irregularly ovoid, setose with partial septum, two sharply arcuate sutures visible.

Pronotum. Pronotum 0.95 times as long as wide, strongly constricted toward apex, widest at base, forming weak transverse impression near apical margin, base weakly bisinuate. Surface smooth, shining, punctures on central portion of disc fine, shallow, moderately dense, space between punctures equal to four times that of point diameters, punctures larger and dense laterally and on apical constriction. Apical and anterolateral margins bearing sparse, erect, yellow, hairlike setae.

Elytra. 1.13 times as long as wide (paratypes 1.11), 1.30 times as long as pronotum (paratypes 1.32). Sides subparallel on apical half, evenly rounded on apex. Disc punctured by straight rows of deep punctures, distance between punctures equal to double that of point diameters. Interstriae greater than twice width of striae, weakly impressed, with straight rows of small points, distance between punctures equal to four times that of points diameters. Declivity bearing sparse, short, erect yellow scaly setae, elytra apex slit along both sides with few, long, erect yellow setae.

Metepimeron greater than half-length of the metepisternum.

Abdomen. Suture on the posterior margin of ventrite 1 slightly thickened. Ventrite 2 nearly perpendicular to ventrite 1, surface shining with slightly large punctures; setae moderately dense, scaly, short, erect. Large median spine is situated in the middle of ventrite 2 base, its length is almost the same length as ventrite 1, apex of the spine is pointed and bent up; suture on the posterior margin of ventrite 2 not thickened, but only weakly elevated relative to the base of the next ventrite. Sutures on the posterior margin of ventrites 3 and 4 weakly elevated relative to the base of the next ventrite. Ventrite 5 is black colored and is a half-elliptical shape; length of ventrite 5 greater than the combined lengths of ventrites 3 and 4.

Genitalia. ( Figs. 2 A–C ). Aedeagus 0.85 mm long, moderately stout, weakly sclerotized. Penis apodemes are a little longer than penis body. Small grains concentrated in the middle of penis apodemes. The apical part of penis is narrow and elongate. Gastric spiculum about 0.67 mm long, curving with two forks. Tegmen is short Y-shape.

Female. ( Figs. 1 G–L ). 4.3–4.4 mm long (mean = 4.37; n = 4); 2.2–2.4 times as long as wide. Similar to male except that the frons is convex, the slightly raised blunt tubercle above epistoma, central portion of frons punctured by deep points, long bristle-like setae under the eye lateral areas sparser than male ( Figs. 3 ); pronotum as long as wide; apex of spine on ventrite 2 is situated at the same horizontal level as its base.

Etymology. The species name makes reference to the tubercle of the allotype female frons.

Sequence Data. The DNA was extracted from a paratype specimen collected from the same elm tree (GenBank: COI, Accession No. LC 739369; 28S, Accession No. LC 739367; CAD, Accession No. LC 739368) .

Biology. S. unicornis is a typical bark beetle, this species is monogamous. On June 28, 2022, the adults were found on the tree trunks of Ulmus sp. that were between 5 and 9 cm in diameter. A small series, consisting of a few adults, was collected by bark dissection. The galleries ( Fig. 2 ) consisted of a single longitudinal egg gallery (about 4.0 cm long) with a large nuptial chamber. The egg gallery strongly scored the sapwood; the larval mine (about 5 cm long) lightly scored the sapwood and extended radially to both sides. It is noteworthy that the type of S. squamosus was also found in the sampled individual elm tree.

Figures

FIGURE 1 Scolytus unicornis. A) dorsal male habitus; B) lateral male habitus; C) male frons; D) male frons oblique; E) male venter; F: male venter oblique; G) dorsal female habitus; H) lateral female habitus; I) female frons; J) female frons oblique; K) female venter; L) female venter oblique.

FIGURE 2 Scolytus unicornis, male genitalia. A) gastric spiculum; B) tegmen from ventral view; C) dorsal view.

FIGURE 3 Scolytus unicornis female frons.