A taxonomic review of the genus Horniolus Weise from China, with description of a new species (Coleoptera, Coccinellidae)

Abstract Five species of the genus Horniolus Weise, 1901 from China are revised, including the description of a new species, Horniolus hainanensis Chen & Ren, sp. n. Horniolus sonduongensis Hoàng, 1979 is reported from China for the first time. A key to the species from China is provided. Nomenclatural history, diagnoses, detailed descriptions, illustrations, and distribution for each species have been provided. A checklist of all known species of this genus is also presented.


Introduction
The genus Horniolus was proposed by Weise (1901), with type species Horniolus dispar Weise described from Sri Lanka by monotypy. Bielawski (1961) pointed out that the species described as Scymnus (Pullus) sp. from Sri Lanka by him (Bielawski 1957) was H. dispar. Miyatake (1963) provided a detailed description of Horniolus, transferred Scymnus fortunatus Lewis, 1896 to this genus, and described three additional species from Japan. Subsequently, six more species from China (Hong Kong and Taiwan), India, Malaysia (North Borneo), Thailand and Vietnam were added by him to this genus (Miyatake 1976(Miyatake , 1979. Hoàng (1979) described H. sonduongensis from Vietnam. Booth and Pope (1989) transferred Scymnus guimeti Mulsant, 1850 to Horniolus based on the examination of the type material deposited in the Hope Entomological Collections. Sathe and Bhosale (2001) described H. mirajensis from India, but it was synonymized with Propylea dissecta (Mulsant, 1850) by Poorani (2004). Recently, Poorani (2015) described H. sororius from India. Prior to the present study, only 14 species have been recognized in this genus, occurring from East to South and Southeast Asia, and most species are poorly represented in collections.
Horniolus has been placed in the tribe Scymnini, which was included in the subfamily Scymninae by earlier workers such as Sasaji (1971), Pang and Gordon (1986), Fürsch (1996) and Poorani (2002). However, Korschefsky (1931) assigned this genus to the tribe Ortaliini within the subfamily Coccinellinae in his catalogue. Recent phylogenetic study on classification of Coccinellidae using both molecular and morphological data has showed that Horniolus Weise and Rodolia Mulsant form a clade placed within the tribe Coccidulini in the broadly defined subfamily Coccinellinae (Seago et al. 2011).
In the present paper, five species of the genus Horniolus from China are revised, with the addition of a new species. All the species are illustrated and described in detail.
A key to and distribution map for the species from China are given. A checklist of the species of Horniolus around the world is also provided.

Material and methods
Specimens examined were collected from China and Vietnam, and deposited in the Department of Entomology, South China Agricultural University, Guangzhou, China (SCAU). In addition, the holotypes of H. novempunctatus and H. hisamatsui were obtained from the collection of the Entomological Laboratory, Ehime University, Matsuyama, Japan (ELEU).
The morphological terms follow Ślipiński (2007) and Ślipiński and Tomaszewska (2010). Measurements were made using a micrometer attached to a SteREO Discovery V20 dissecting stereoscope and are defined as follows: TW total width, across both elytra at widest part; TH total height, at highest part of elytra in lateral view; TL total length, from apical margin of clypeus to apex of elytra; PL pronotal length, from the middle of anterior margin to the base of pronotum; PW pronotal width at widest part; EW elytral width, equal to TW; EL elytral length, along suture from base to apex including scutellum; HW head width, at widest part including eyes.
Male and female genitalia were dissected, cleared in a 10% solution of NaOH by boiling for several minutes, and placed on slides for further study. Photographs of the whole beetles and their genitalia were taken according to Chen et al. (2015).
Description. Body rounded or elongate oval, moderately convex, with dense pubescence, widest around middle of elytra.

Key to the species of the genus Horniolus from China
Head with fine frontal punctures, as large as eye facets, 0.5-1.0 diameter apart. Eyes finely faceted, interocular distance 0.56 times head width. Pronotal punctures Diagnosis. This species is similar to Horniolus amamensis Miyatake and Horniolus kyushuensis Miyatake in general appearance, but can be separated from the latter by having incomplete abdominal postcoxal lines (Fig. 3d) and broader body outline (Fig. 3a). The stout penis guide ( Fig. 3g-  Body rounded, moderately convex, dorsum covered with white pubescence (Fig.  3a-c). Head black (Fig. 3b). Antennae and mouthparts dark brown. Pronotum and scutellum black. Elytra black with four yellowish spots, first pair transverse, almost straight, parallel to elytral base, situated at anterior ⅓ length of elytra; second pair comma-shaped, located in apical ⅓ length, not reaching suture and lateral margins (Figs 3a, 3c). Prothoracic hypomeron and prosternum black. Mesoventrite and metaventrite black. Elytral epipleuron dark brown with inner and outer margins black. Legs black except tarsi brown.
Head with coarse frontal punctures, distinctly larger than eye facets, 0.5 diameter apart. Eyes finely faceted, interocular distance 0.53 times head width. Pronotal punctures smaller than those on frons, 1.0-2.0 diameters apart. Surface of elytra with punctures larger than those on pronotum, separated by 1.0-2.0 diameters. Prosternal carinae Y-shaped with stem ⅓ as long as arm, arms broadly separated. Abdominal postcoxal lines strongly recurved and distinctly incomplete laterally (Fig. 3d), reaching 4/5 length of abdominal ventrite 1, area enclosed by lines coarsely punctate, narrowly smooth along line. Abdominal ventrite five weakly emarginated apically in male.
Male genitalia. Penis stout, evenly curved (Fig. 3e); penis capsule with long inner arm and short outer arm; apex of penis slightly expanded (Fig. 3f). Tegmen stout (Figs 3g-h) with penis guide parallel-sided from base to ¾ length, then tapering gradually to blunt apex in ventral view (Fig. 3g). Parameres tapering toward apex, shorter than penis guide, densely covered with long setae at apices (Fig. 3h). Diagnosis. This species closely resembles Horniolus dispar Weise in elytral pattern and male genitalia, but can be distinguished from it by having dark brown pronotum with black marking (Fig. 4a) and the penis guide distinctly shorter than paremeres (Sasaji 1971 Body elongate oval, slightly convex, dorsum covered with white pubescence (Fig.  4a-c). Head, antennae and mouthparts dark brown. Pronotum dark brown with black marking at middle. Scutellum black. Elytra black with four reddish brown, transverse spots, first pair distinctly sinuated, located before middle in anterior half; second pair smaller, constricted medially, located apical ¼ length of elytra. Prothoracic hypomeron dark brown. Prosternum dark brown to black. Mesoventrite, metaventrite and elytral epipleura black. Legs dark brown.
Head with fine frontal punctures, slightly larger than eye facets, 1.0-2.0 diameters apart. Eyes finely faceted, interocular distance 0.54 times head width. Pronotal punctures as large as those on frons, 1.0-2.0 diameters apart. Surface of elytra with punctures larger than those on pronotum, separated by 2.0-3.0 diameters. Prosternal carinae Y-shaped with stem 1/7 as long as arm, arms narrowly separated. Abdominal postcoxal lines strongly recurved and complete laterally (Fig. 4d), reaching 5/6 length of abdominal ventrite 1, area enclosed by lines coarsely and sparsely punctate, broadly smooth along line.
Male genitalia not studied in the present paper. According to the descriptions and illustrations given by Sasaji (1971: 118), the penis is stout and distinctly convergent apically; penis capsule with long inner arm and short outer arm; apex of penis simple without membranous appendage; tegmen stout with penis guide boat-shaped, widest at base, then tapering gradually to pointed apex in ventral view; parameres strongly curved at base, longer than penis guide, sparsely covered with long setae at apices.
Remarks. This species has variable pronotal colouration (Miyatake 1963). Lewis (1896) described this species in the genus Scymnus Kugelann based on only one specimen from Japan. In his original description, Lewis found a Ceylonese species which closely resembled this species. Ohta (1929) listed this species under Scymnus (s. str.) without examining any specimens, and this treatment was followed by Mader (1955). Kamiya (1961) assigned this species to the subgenus Scymnus (Pullus) Mulsant due to the complete abdominal postcoxal line. He also indicated the peculiar character of prosternal carinae and described the male genitalia. Miyatake, 1976 Figs 5, 7 Horniolus hisamatsui Miyatake, 1976: 29;Pang and Gordon 1986: 187;Yu and Lau 2001: 152;Canepari 2003: 262;Pang et al. 2004: 89;Kovář 2007: 579;Ren et al. 2009: 58. Diagnosis. This species is similar to Horniolus vietnamicus Miyatake in general appearance and male genitalia, but can be distinguished from it by the first pair of elytral spots with hind margin deeply emarginated at middle (Fig. 5a, d) and penis guide shorter than parameres (Fig. 5l). In H. vietnamicus, the first pair of elytral spots has straight hind margins and penis guide is as long as parameres. Body elongate oval, slightly convex, dorsum covered with white pubescence (Fig.  5a-f). Head, antennae and mouthparts reddish brown. Pronotum reddish brown. Scutellum dark brown. Elytra black with 4 yellowish brown, transverse spots, first pair of spots with anterior margins sinuated, hind margins deeply emarginated at middle, located behind middle in anterior half; second pair smaller, comma-shaped, located at apical ¼ length of elytra. Prothoracic hypomeron and prosternum reddish brown. Mesoventrite, metaventrite and elytral epipleura reddish brown. Legs brown.

Horniolus hisamatsui
Head with fine frontal punctures, as large as eye facets, 1.0-2.0 diameter apart. Eyes finely faceted, interocular distance 0.48 times head width. Pronotal punctures larger than those on frons, 1.0-2.0 diameters apart. Surface of elytra with punctures slightly larger than those on pronotum, separated by 2.0-3.0 diameters. Prosternal carinae Y-shaped with stem approximately ⅓ as long as arm, arms broadly separated. Abdominal postcoxal lines strongly recurved and complete laterally (Fig. 5h), reaching ¾ length of abdominal ventrite 1, area enclosed by lines coarsely punctate, broadly smooth along line. Abdominal ventrite 5 in male with apex truncate.
Male genitalia. Penis stout, evenly curved (Fig. 5i); penis capsule with long inner arm and indistinct outer arm; apex of penis slightly expanded with membranous appendage (Fig. 5j). Tegmen stout (Fig. 5k-l) with penis guide parallel-sided at basal half, widest at middle in ventral view (Fig. 5k); in lateral view, penis guide robust at basal ⅔ length, then abruptly narrowed in apical ¼ th and produced into a sickle-shaped, acutely pointed apex (Fig. 5l). Parameres narrowed toward apex, longer than penis guide, densely covered with long setae at apices and inner side (Fig. 5l).  Fig. 5g).

Horniolus sonduongensis
Head with coarse frontal punctures, slightly larger than eye facets, 0.2-0.5 diameter apart. Eyes densely faceted, interocular distance 0.54 times head width. Pronotal punctures smaller than those on frons, 2.0-3.0 diameters apart. Surface of elytra with punctures much larger than those on pronotum, separated by 1.0-2.0 diameters. Prosternal carinae Y-shaped with stem approximately ⅓ as long as arm, the arms broadly separated. Abdominal postcoxal lines strongly recurved and complete laterally (Fig.  6j), reaching ¾ length of abdominal ventrite 1, area enclosed by lines coarsely punctate, narrowly smooth along line. Abdominal ventrite 5 in male with apex weakly emarginated medially.
Male genitalia. Penis slender and long (Fig. 6k); penis capsule with long inner arm and short outer arm; apex of penis swollen and curved outwardly (Fig. 6l). Tegmen stout (Fig. 6m-n) with parallel-sided at basal half, then tapering gradually to a blunt apex in ventral view (Fig. 6m). Parameres narrow and curved apically, slightly shorter than penis guide, densely covered with long setae at apices (Fig. 6n).