Mochtherus luctuosus Putzeys

Hunting, Wesley & Yang, Man-Miao, 2019, A taxonomic review of the pericaline ground-beetles in Taiwan, with descriptions of new species (Coleoptera, Carabidae, Lebiini), ZooKeys 816, pp. 1-164 : 126-131

Mochtherus luctuosus Putzeys Figs 95, 96 A–D, 102A, 103

Mochtherus luctuosus Putzeys, 1875: pl. Lll; Bates 1883: 281; Csiki 1932: 1382; Jedlička 1963: 353; Lorenz 2005: 460.

Sinurus nitidus Bates: Habu, 1953: 50.

Sinurus luctuosus Putzeys: Habu and Baba, 1957: 17; Habu 1959: 9.

Dolichoctis (Mochtherus) uenoi Habu, 1967: 108. syn. n.

Types and other material examined.

39 specimens of M. luctuosus : 25 males and 14 females. For further details see EH Strickland Virtual Entomology Museum Database.

Type locality.

Japan. "S. Nipon".

Taxonomic notes.

When Habu (1967) described Mochtherus uenoi from Taiwan, he acknowledged that it very closely resembled M. luctuosus . He based his description primarily on differences in two characters, pronotum form, and endophallus apex form. Upon examination of several specimens of this species, it became apparent that there was variation in both of these characters, as well as significant variation in overall body length.

Phallus apex form hardly differs from specimen to specimen; however, some individuals do have a slightly more pointed apex than others. Habu’s illustration of this is well within the range of variation observed. Variability in pronotum characteristics in this species is somewhat dramatic and if Habu had access to more material, he likely would have noticed that pronotum variation exists, even within local populations. Pronotum disc convexity is variable. Some individuals have a disc that is more convex and broadly rounded, while others are flatter in appearance. Pronotum margins are also variable. Some individuals have margins that are wider and more up-turned at the margins. This character can change the appearance on the sinuate baso-lateral margin that is typical of Mochtherus , making the sinuation appear less pronounced. Despite these differences, this species is easily distinguished in Taiwan as it is the only entirely black Mochtherus species present.

During the course of this work, a few specimens of the genus Sinurus looked very similar to specimens regarded as M. luctuosus from Taiwan. Non-type material from the type series of both Sinurus nitidus Bates and Sinurus graciliceps Bates were dissected and the genitalic characters were very similar to all Mochtherus species examined.

Considering the variability observed within specimens of the species M. luctuosus from Taiwan, both of these Sinurus species belong in the genus Mochtherus and are likely conspecific with M. luctuosus . One female specimen of S. opacus Chaudoir, which was the first species described in Sinurus , was also dissected. It differs from the other two species in that the elytral microsculpture is granulated and the elytral margins are faintly serrate. The specimen was not in excellent condition but it was apparent that the general form of the gonocoxite, spermatheca, and associated gland were all very similar to that of Mochtherus species. It is possible that further work will show that this genus is congeneric with Mochtherus .

Diagnosis.

Specimens of this species are easily distinguished from other species of Mochtherus by the entirely black dorsal coloration,

Description.

OBL 7.50 - 11.00 mm. Length (n = ten males, ten females): head 0.72 - 0.90, pronotum 1.40 - 1.84, elytra 4.50 - 6.08, metepisternum 1.04 - 1.40 mm; width: head 1.44 - 1.92, pronotum 1.40 - 1.84, elytra 3.33 - 4.33, metepisternum 0.60 - 0.84 mm.

Body proportions. HW/HL 1.91 - 2.14; PWM/PL 1.36 - 1.53; EL/EW 1.24 - 1.45; ML/MW 1.42 - 1.89 mm.

Color. Fig. 95. Dorsum of head piceous, with small, diffuse patch just before clypeal suture, brunneous to brunneo-piceous, clypeus and labrum brunneous, some specimens with labrum darker centrally; palpi and antennae brunneous; pronotum disc brunneo-piceous to piceous, margins brunneous to piceous; elytral disc brunneous, dark, to piceous, suture and margins slightly lighter; ventral surface of head, metepisternum and lateral margins darker than other ventral surfaces, brunneous to piceous, all other surfaces brunneous, lighter to darker; legs brunneous to rufo-brunneous, most specimens with ventral surface of tibia darker, brunneo-piceous to piceous.

Microsculpture. Dorsum of head with mesh pattern somewhat granulate, isodiametric, somewhat transverse towards neck, clypeus with sculpticells stretched longitudinally, labrum with sculpticells shallow, almost isodiametric; pronotum with microsculpture transverse; elytra with sculpticells transverse; ventral surfaces with microsculpture transverse.

Macrosculpture and pilosity. Dorsum of head with scattered setigerous punctures, setae short and punctures fine, not distinctively visible, labrum with a few short setae in apical half; mandible with a few short setae just beyond apex of scrobe; pronotum with scattered setigerous punctures, punctures fine, setae short but uniform in length and longer than the setae of both head and elytra; elytral intervals with scattered setigerous punctures, setae short and punctures fine, not distinctively visible; striae with +/- evenly spaced setigerous punctures along length, both punctures and setae so fine that they are hardly visible at 50 ×; ventral surface with randomly scattered setigerous punctures, setae relatively dense and easily visible in lateral view.

Fixed setae. Elytra with two setae in interval 2, one seta posterior to apical 1/3, one seta posterior to apical 1/6.

Luster. Dorsal surface moderately glossy; ventral thoracic sterna and abdominal sterna moderately glossy.

Head. Labrum faintly emarginate, longer than wide; mentum with broad tooth; eyes convex.

Pronotum. Lateral margins wide, distinctively spatulate and turned up at edges, sinuate from lateral seta to base but edges rounded, not as dramatic as other Mochtherus species, basal angles obtuse, rounded; apical margin distinctly emarginate, large apico-lateral lobes; anterior transverse impression shallow, posterior transverse impression moderately shallow; median longitudinal impression moderately deep.

Legs. Tarsal claws pectinate, 3-4 denticles per claw.

Male genitalia. Fig. 96 A–D. Length 1.04 - 1.32 mm. Phallus slightly expanding towards apex in ventral view, terminating bluntly at apical area, apex, short and broad, distinctively spatulate and positioned on the right side of phallus in ventral view; endophallus expanding and angled from mid-length, one basal lobe, one basal microtrichial field (mtf), microtrichia moderately long.

Female genitalia. Fig. 102A. Width 1.00 - 1.08 mm. Two lateral ensiform setae (les). One spermatheca (sp1), cylindrical and elongate tapering towards apex, length undetermined due to breakage; ring sclerite (srs) separating spermatheca duct from spermatheca, thin; one spermathecal accessory gland (sg), spermathecal gland duct (sgd) relatively long, attachment site medially on dorsal surface of ring sclerite when viewed from ventral aspect.

Habitat, habits, and seasonal occurrence.

The known elevational range of M. luctuosus is from 230 to 2000 meters. Adults are found in mixed primary and secondary forest of montane areas, as well as disturbed areas, and are crepuscular or nocturnal with most activity observed on tree trunks and deadwood at night. Several specimens were collected from the trunks of fallen trees. All other specimens were hand collected.

Geographical distribution.

Mochtherus luctuosus is known from Japan and Taiwan. For Taiwan collecting localities see Figure 103.