Amphimenes Bates, 1873

Fedorenko, Dmitry N., 2010, New or little-known species of the genus Amphimenes Bates, 1873 (Coleoptera, Carabidae, Lebiinae) from Vietnam, ZooKeys 65, pp. 17-50 : 18-21

Amphimenes Bates, 1873

Amphimenes piceolus Bates, 1873: 322 (Nagasaki, Japan; by monotypy) [Type-species].

Redescription.

Small- to medium-sized pericaline lebiines, either unicoloured or with a pale pattern composed of two, posthumeral and subapical, rounded, yellow spots on each elytron, latter spots adjoining suture; reflexed side margins of both pronotum and elytra, antennae, mouthparts, legs, labrum and clypeus usually paler, often contrastingly so. Body glabrous, except for underside microscopically ciliate and pronotum almost indistinctly so in some species. Forebody dorsum dull due to an almost granulate isodiametric microsculpture occupying head, pronotum and scutellum, sometimes somewhat shining because of a weaker microsculpture which, in addition, forms slightly transverse meshes behind pronotal front margin and base. Elytral microsculpture composed of very fine and dense transverse lines or very narrow transverse meshes, anyway contributing to dorsum’s iridescence, rarely coarse and isodiametric. All but one congener show a highly characteristic cross-striated sculpture occupying entire disc or, rarely, only elytral base; this cross-striation, combined with microsculpticells or lines, becoming increasingly oblique outwards, resulting in both being conspicuously oblique posterolaterad on intervals 5 to 8.

Eyes varying from large and hemispherical to small and flat. Labrum trapezoidal (Fig. 1), a little narrowing forwards, with front angles rounded; anterior margin slightly sinuate, with six setae of gradually decreasing length inwards. Last maxillary palpomere narrowing apicad, longer than penultimate one. Submentum with a pair of strong setae; another pair situated at base of a large median tooth of mentum, latter rounded apically, about half as long as wide lateral lobes (Fig. 2). Ligula well-developed, sclerotized apically and not so strongly basally, fairly narrow, with two pairs of apical setae, inner much longer than outer; paraglossae membranous, wide, a little longer than ligula, each with four setae over outer margin. Penultimate labial palpomere with two preapical setae drawn together; proximal and distal setae of anterodorsal and anteroventral position, respectively; last labial palpomere subcylindrical, slightly narrowing apicad. Antennae long to short, pubescent from apical half of antennomere 4 onward, some species ( Amphimenes medius , Amphimenes minutus , Amphimenes rufipes ) showing apical half of antennomere 3 spa s ly ciliate along outer margin; 3rd antennomere 1.2-2.05 times as long as 2nd; 7th to 9th 1.22-3.34 times as long as wide.

Pronotum rather flat, strongly transverse to about as long as wide, weakly cordate, deeply emarginate anteriorly, with protruding and fairly narrow front angles, rather strongly rounded on sides, somewhat narrowing basad, broadest before middle, i.e. level to anterolateral setigerous pore at which side margin often slightly angulate; latter moderately strongly sinuate to straight before posterior angles, these varying from obtuse to almost indistinct due to pronotal base increasingly oblique forward towards posterolateral setigerous pore. Front margin with a very narrow but distinct polished bead; side margin rather strongly explanate-reflexed, narrow anteriorly and gradually broadening basad; basal transverse depression conspicuous to weak, when well-developed, ca 0.15 times as long as pronotum along mid-line, latter varying from deep to superficial; lateral basal foveae weak to indistinct, each usually extended to the middle or anterior third as a very shallow depression running parallel to side margin; disc at middle with a pair of small and shallow paramedian foveae. Base slightly trilobed, with medial part mostly a little surpassing lateral lobes.

Metathorax longer in winged than in wingless species; accordingly, metepisternum much longer than wide (MESL/W=1.35-1.73) in the former versus about as long as wide (MESL/W=0.78-1.02) in the latter.

Elytra subrectangular to oval, subparallel to rather strongly rounded on sides, with base wide to very narrow and shoulders slightly to completely rounded; apical truncature oblique and slightly sinuate between outer angle of each elytron and its apex, those rounded in all but one species. Striae impunctate, deep throughout, intervals mostly convex. Discal setigerous pores three or two (either D1+D3 or D2+D3), adjoining stria 3 (D1) or 2 (D2, D3). Prescutellary pore present. Preapical setigerous pores (those of 7th interval) two, outer (anterior) large, inner (posterior) small. Umbilicate series uninterrupted or divided into two, posthumeral and subapical, groups.

Profemur rather strong. Claws serrate in basal two-thirds. Pretarsus with two or only one, distal, pair of setae beneath.

Aedeagus. Penis mostly rather stout, weakly arcuate, strongly bent to the right just behind basal ca s le and often twisted to the right behind the middle, with apical orifice rounded and shifted to the left; apical lamella rather small, of characteristic shape and structure in different species. Microsculpture usually conspicuous, composed of is odiametric to slightly longitudinal meshes predominantly developed over left side; right ventral side mostly longitudinally striate in basal half. Parameres moderately strongly reduced, left paramere subrectangular, right one small, rounded apically, with base long, narrow and hooked apically.

Female gonapophyse as in Fig. 3.

Sexual dimorphism: male protarsomeres 1-3 dilated, each with an adhesive pubescence beneath, sternite 6 sometimes slightly desclerotized or weakly emarginate posteriorly, with one, lateral, pair of setae, versus not sinuate and with two pairs of setae in female. Males of two species show basal third of profemur underside furnished with a small tubercle instead of a pointed mesotrochanteral tubercle observed in males of most other congeners.

Geographic distribution.

The range of the genus extends from Japan (Kyushu and Shikoku) in the north and east to at least southern Vietnam in the south, and Myanmar in the west. Winged congeners are certain to be much more widespread than wingless ones, implying still undescribed species of very local ranges to be discovered in unexplored montane regions of Indochina , Vietnam in particular.

Habits and habitats.

All congeners inhabit forested areas, both montane and lowland. Original adult habits seem to be strictly subcortical. In southern Vietnam, species with such habits occur under bark ( Amphimenes bidoupensis ) or also in chapped bark of standing dead trees ( Amphimenes rugulipennis , Amphimenes maculatus ), never of fallen deadwood or logs. All of them are winged, some flying to light at night. Such soil-dwellers as Amphimenes medius , Amphimenes minutus , Amphimenes rufipes and Amphimenes giganteus are certain to be derived, being adapted to living in leaf litter or cavities in logs or fallen larger branches. This has resulted in a few morphological adaptations, among them, the hindwings missing, the elytra wide, fused along the suture, with strongly rounded shoulders, while the eyes tending to be reduced to small and flat. The latter contributes much to the head being narrower across the eyes while broader across the neck, all relative to body width. Only Amphimenes giganteus among the members of the latter ecological group sometimes occurs under bark, while the others have never been observed there. Four species from northern Vietnam show similar morphological adaptaptions, suggesting herpetobiotic habits as well.

In the Bi Doup - Nui Ba Nature Reserve, three to five species live sympatrically, with up to four soil-dwellers among them occurring syntopically. This seems to also be true for elsewhere in Vietnam north of the Dalat Plateau because more than one species have been recorded from such localities as Tam Dao ( Amphimenes reflexicollis , Amphimenes kabakovi ), Quỳ Châu ( Amphimenes gracilis , Amphimenes planicollis ) or Thai Nguen ( Amphimenes gracilis , Amphimenes nitidus ).

Generic composition.

The genus currently includes 16 species arranged into five species groups. Of them, two, the rugulipennis-group ( Amphimenes rugulipennis , Amphimenes maculatus ) and the piceolus-group ( Amphimenes piceolus , Amphimenes riukyuensis , Amphimenes montanus , Amphimenes bidoupensis , Amphimenes gracilis , perhaps also Amphimenes asahinai ) comprise congeners of subcortical habits. The medius-group ( Amphimenes giganteus , Amphimenes medius and Amphimenes minutus ) and the planicollis-group ( Amphimenes planicollis , Amphimenes reflexicollis , Amphimenes nitidus and Amphimenes kabakovi ) are established here for soil-dwelling species distinguishable chifly in a particular formula of the elytral discal chaetome. This is also true of Amphimenes rufipes which seems to constitute a group of itself.

Key to species of

Amphimenes