Madrasostes deharvengi Gao, 2009

Ballerio, Alberto & Maruyama, Munetoshi, 2025, Review of Madrasostes Paulian, 1975 (Coleoptera: Hybosoridae: Ceratocanthinae) from Vietnam, with remarks on its generic limits, Zootaxa 5661 (3), pp. 420-430 : 421-424

Madrasostes deharvengi Gao, 2009

( Figs. 2 ; 4C )

Madrasostes deharvengi Gao, 2009: 155 (description and iconography).

Type locality. Yachang National Nature Reserve , Leye County, northwest of Guangxi Autonomous Region, China .

Material examined. Vietnam: 5 ♂♂, 2 ♀♀ and 1 specimen of sex unstated (NSMT, KUM, ABCB): Ban Ba Pha, 250m Phin Ho, Sin Ho , Lai Chau prov. / [N. Vietnam] 26.V.1998 S. Nomura leg.

Redescription. Size: HL = 0.92 mm; HW = 1.34 mm; PL = 1.53 mm; PW = 2.25 mm; EL = 2.30 mm; EW = 2.12 mm. Small-sized Madrasostes . Flightless. Body strongly convex. Black with reddish-brown tinge (especially on pronotum), dorsum setose (50×), underside, tarsi and antennae dark reddish-brown, setation yellowish-brown.

Head: W/L ratio = 1.48; subpentagonal, clypeal apex obtuse, apical projection very weak, rounded and sexually dimorphic, sides irregularly rectilinear; genal canthus present, short and not reaching occipital area, dorsal ocular area short and narrow ( Fig. 2F ), ventral ocular area small and transverse, genae acute, protruding outwards, genal suture short and hardly visible; head dorsal surface covered by large dense impressed horseshoe-shaped punctures encasing another smaller horseshoe-shaped puncture bearing in the middle a fine erect seta slightly longer than maximum punctural diameter, all punctures centripetally oriented, vertex with dense large simple punctures. Antennae with ten antennomeres. Pronotum: subrectangular (dorsal view) (W/L ratio = 1.50), convex and without tubercles or carinae, fore angles broadly subtruncate ( Fig. 2F ); pronotal base regular without basal carinae, pronotal punctation uniformly covering pronotal surface, consisting of large dense ocellate punctures, each ocellum encasing another smaller one bearing a fine erect seta in the middle, setae slightly longer than maximum ocellate puncture diameter, interpunctural distance inferior than ocellum diameter (ocellate punctures almost touching each other). Scutellum : base narrow and almost smooth, remaining surface covered by dense short transverse strongly impressed irregular comma-shaped punctures each one encasing a smaller ocellate puncture bearing a fine seta in the middle. Elytra : longer than wide (W/L ratio = 0.92), subogival with subacute distal third (dorsal view), strongly convex; humeral callus indistinct; elytral surface uniformly covered by large horseshoe-shaped punctures, shallower than pronotal punctation, short on basal third and longer on median third encasing another smaller horseshoe-shaped puncture bearing in the middle a fine erect seta slightly longer than pronotal ones, apical third with dense elongate ocellate punctures, each one encasing a smaller one; inferior sutural stria indistinct, striated articular area hardly visible in lateral view, relatively narrow and short; marginal area medium-sized and explanate; elytral articular process developed, smooth and shiny, with a deep line bordering scutellar sides. Wings: flightless. Legs: protibiae with outer margin irregularly serrate, ending with two apical teeth, apical spur strongly developed and sexually dimorphic. Mesotibiae ending with a single apical spur. Metatibiae ending with two apical spurs. Sexual dimorphism : males have the inner apex of mesotibiae hooked (bent inwards at a right angle and pointed). Apical spur of protibiae bent inwards in both sexes but males have it much larger and clavate ( Fig. 2F ), whereas in females the apex is sharp, finally the clypeal apex has a weak rounded projection in males while in female the projection is slightly more developed. Male genitalia: aedeagus (L = 1.3 mm) with parameres acute and relatively long as in Fig. 2H , internal sac with a large elongate sclerite (the “dumbbell like” sclerite of Gao’s original description), spiculum gastrale (L = 1.2 mm) with short apodeme and long rounded branches as in Fig. 4C .

Distribution and habitat. This is the first record for Vietnam, the species was previously known from Guangxi ( China) only. To our knowledge only the type series was known till now, made of two male specimens collected from a soil sample using Berlese funnel in the Yachang National Nature Reserve. The area of the Vietnamese record falls within the Northern Indochina Subtropical Forests ecoregion ( Wikramanayake et al. 2002).

Remarks. The identification of M. deharvengi was made possible thanks to several photographs of the holotypus sent to the first author by Lei Gao prior to its formal description. The generic placement of M. deharvengi within Madrasostes remains somewhat problematic. In the context of a comprehensive revision of the genus—which is still far from complete due to a lack of available material, limited knowledge of species-level diversity, and numerous undescribed taxa known to the first author—this species may ultimately warrant placement in a separate genus.

The male genitalia of M. deharvengi are strikingly similar to those of Pterorthochaetes Gestro, 1898 , particularly in the shape of the spiculum gastrale, which possesses a short apodeme and long rounded branches, and the parameres, which are dorsally flattened and sharply pointed. Furthermore, the mesotibiae bear a single apical spur, a character observed in both Pterorthochaetes and Oxymorostes Ballerio, 2009 , but not in other members of Madrasostes . However, M. deharvengi differs from Pterorthochaetes in having ten antennomeres (nine in Pterorthochaetes ) and female genitalia lack bursal sclerites (observation made based on a single dissected female). Additionally, the mandibles of the single dissected specimen lack the basal mandibular pore that characterizes the Perignamptus generic group (see Ballerio 2009), thus also distinguishing this species from Oxymorostes . The species further deviates from typical Madrasostes in having a subogival elytral shape in dorsal view. These combined features suggest that the species occupies an unusual position within the heterogeneous genus Madrasostes and may deserve generic re-evaluation in the future.

Figures

FIGURE 2. Madrasostes deharvengi Gao, 2009. A. Distended adult in dorsal view. B. Rolled-up adult in ventral view. C. Rolled up adult in dorsal view. D. Rolled-up adult in lateral view. E. Rolled-up adult in posterior view. F. Detail of male fore tibia, showing clavate apical spur (ap), genal canthus (gc) and subtruncate fore angles of pronotum. G. Head of male in dorsal view. H. Aedeagus in dorsal, ventral and lateral views.

FIGURE 4. Spicula gastrales of A. Madrasostes nomurai Ballerio & Maruyama sp. nov., B. Madrasostes bartolozzii Ballerio, 2013 and C. Madrasostes deharvengi Gao, 2009.