Metabacetus willi, Gueorguiev, Borislav V., 2013

Gueorguiev, Borislav V., 2013, On five species of the tribes Abacetini and Pterostichini (Coleoptera, Carabidae), ZooKeys 352, pp. 35-50 : 37-39

Metabacetus willi sp. n. Figs 1-8, Table 1

Type material.

Holotype ♂, "INDONESIA, Java cave Seplawan 2.VI.1994, leg. P. Beron" [typeset], "HOLOTYPE Metabacetus willi spec. nov. Guéorguiev des. 2012" [typeset, red label] (NMNHS). Paratypes 4♂♂, 3♀♀, labelled as follow: 3♂♂, 1♀, "INDONESIA, Java cave Seplawan 2.VI.1994, leg. P. Beron" [typeset] (EMEC, BMNH, NMNHS); 1♂, 2♀♀, "INDONESIA, Java v. Kimiri, D.I. Yogyakarta Gua (cave) Nging Rong 29.VIII.1995, P. Beron leg." [typeset] (BMNH, MCNM, NMNHS); all paratypes with subsequently added: "PARATYPE Metabacetus willi spec. nov. Guéorguiev des. 2012" [typeset, red label].

Examined type material of other species.

Metabacetus immarginatus Bates, 1892, syntype ♀, "Carin Ghecù 1300-1400 m L. Fea II-III.88." [typeset], “Typus” [red typeset, white label], " Metabacetus immarginatus Bates" [handwritten], " Metabacetus immarginatus Bates" [handwritten], " Metabacetus , n.g. immarginatus (es. typ.) Bates" [handwritten, yellow label, genus name underlined], "Syntypus Metabacetus immarginatus Bates, 1892" [handwritten & typeset, red label], "Museo Civico di Genova"[typeset] (MCSN). Mateuellus troglobioticus Deuve, 1990, 2♂, 1♀, "Indonesia, Sulawesi Selatan, Bantimurung Gua (Cave) Minpiovo 3.IX.1995, P.Beron leg." (NMNHS).

Diagnosis.

A medium-sized, slightly iridescent species of Metabacetus (Fig. 1), with elongate and attenuate maxillary palpi, last three segments of antennae surpassing the base of pronotum, pronotum widest just after the middle, with anterior margin much shorter than posterior one, sides much narrower anteriorly (than posteriorly), convex posteriorly, lateral fields broadened and moderately reflexed from the middle to the base and obtuse hind angles, prosternum shallowly sulcate medially near apex, apex of elytra without spines, and specific structure of the median lobe of aedeagus (Figs 2-4).

For detailed information about some measurements and ratios see Table 1.

Description.

Habitus. Moderately-sized species of Metabacetus Bates, 1892, with sub-oval and convex body. Measurements. BL: 6.1-6.7 mm (mean 6.375 mm); BW = EW, see below; PL: 1.45-1.6 mm (mean 1.53 mm); PW: 1.85-2.1 mm (mean 1.98 mm); EL: 3.45-3.85 mm (mean 3.59 mm); EW: 2.45-2.8 mm (mean 2.61 mm). Ratios. PW/HW: 1.71-1.81 (mean 1.748); PW/PL: 1.27-1.31 (mean 1.296); PW/PbW: 1.24-1.28 (mean 1.263); PbW/PaW: 1.31-1.34 (mean 1.326); EW/PW: 1.27-1.35 (mean 1.314); PL/EW: 0.42-0.43 (mean 0.429); EL/EW: 1.33-1.4 (mean 1.374). Color. Body dark brown to dark reddish dorsally and ventrally, antennae, legs, pronotal margins, and elytral epipleura paler, reddish, palpi yellowish. Microsculpture and lustre. Very fine, with transverse microreticulation, distinct on head, pronotum, elytra, and most of ventral surface, visible under magnification> 50 ×, indistinct on ventral side of head and middle parts of thorax and abdominal sternites; body very shiny throughout, elytra and less ventral surface with slight spectral iridescence. Head. Longer than wide, narrow in relation to pronotum; disc smooth, frontal furrows deeply impressed, oblique, divergent backward, not reach level of anterior supraorbital punctures; eyes projecting laterally, temporae as long as half diameter of eyes; two pairs of supraorbital setae; paraorbital sulci moderately deep, surpassing level of posterior supraorbital pore backward; antennae long, filiform, densely pubescent from second fourth of segment 4, with terminal three articles surpassing base of pronotum and apex of last antennomere surpassing anterior fifth of elytron; mandibles elongate, with apex pointed and slightly hooked; labrum rectangular, with six setigerous punctures on anterior margin; clypeus trapezoid, rectilinear anteriorly, with two setigerous punctures closer to lateral margins than to anterior one; glossal sclerite of ligula with two long setae on anterior margin; mentum shallowly emarginated, with simple, widely round at tip tooth, pair of labial setae, and deep labial pits, epilobes short, sub-triangular distally, slightly exceeding mentum tooth forward, mentum separated by submentum by distinct labial suture; submentum with four setae, two basal setae longer than lateral ones; maxillary palpomeres glabrous, elongate and attenuate, larger in comparison with labial palpomeres, as long as two third of head length, apical three segments nearly equal in length; labial palpi fusiform, palpomere 2 longer than palpomeres 3, with two long medial setae. Pronotum. Disc-shaped, circular, broader than long, widest just after middle; disc smooth, gently convex medially; midline fine, distinct on medial three fourth of pronotum length, obsolescent apically and basally; anterior sub-marginal sulcus distinct laterally, disappeared medially; anterior and posterior margins of pronotum unbordered, anterior margin scarcely concave, distinctly shorter than posterior one, with fore angles not protruding forward; posterior margin slightly convex backward, hind angles obtuse, incompletely round, not prominent; lateral margins rounded, more anteriorly than posteriorly, without sinuation towards hind angles, lateral fields broadened and moderately reflexed upward towards base, marginal beads continuous, only before hind angles obsolescent; anterolateral seta at anterior second quarter, posterolateral seta at hind angle; posterolateral impressions deep, as long as quarter of pronotum length or so. Elytra. Ovoid, wide, rather convex dorsally, slightly narrower basally, with shoulders rounded, widened toward behind as parallel-sided along anterior two thirds, widest along medial third, distinctly sinuate before apex, apices of each elytron rounded at tip; epipleurae with distinct external plicae; striae complete, deeply impressed, internal six striae feebly punctate, striae 7-9 pronouncedly punctate; parascutellar striae present, anastomosing with stria 1; scutellar setigerous pores present, on base of striae 2, slightly removed back from basal margin with distance of diameter of pore or so; basal margin complete; discal setigerous punctures absent; stria 7 with two setigerous punctures near to apex, subapical puncture larger than apical one; intervals moderately convex; umbilicate series of elytra in stria 8, shortly interrupted in middle, consist of 14 setigerous punctures. Hind wings. Well-developed. Ventral surface (thorax and abdomen). Prosternum and proepisterna smooth and glabrous, prosternum only shallowly sulcate medially along apex, prosternal process unbordered; mesosternum smooth, metaepisterna elongate, impunctate, longer than wide, strongly narrowed posteriorly, with wide anterior margins and very short posterior ones; metasternum smooth, only laterally with three-four large punctures from each side, deeply grooved laterally. Abdomen glabrous except one pair paramedial setae on sterna IV–VI, sternum VII with one pair sub-apical setae in males, with two pairs of sub-apical setae in females; sternum II with cluster of deep punctures laterally. Legs. Moderately slender and long; protrochanter with one seta; profemur anterior face with a few very short setae, ventral face glabrous, posterior face with three long setae, two medial and one subapical, dorsal face with three-four short setae; mesocoxa with two setae, one medial and one lateral; mesotrochanter with one distal seta; mesofemur anterior face with four long setae, two basal and two medial ones, dorsal face with 7-9 short setae arranged in one-two rows along length, posterior face with several short setae, ventral face glabrous; metacoxa with two lateral setae, one anterior and one posterior, medial transverse sulcus deep and sinuate, not reaching external coxal margin, distant from anterior margin; metatrochanter slightly shorter than half length of metafemur, with one proximal seta, elongate, apex pointed; metafemur anterior face with one basal and one medial (near ventral edge) setae, dorsal face with one rather short seta at distal third, posterior and ventral faces glabrous; structure of pro-, meta-, and metatibia, as well as of tarsomeres in accordance with that described by Will and Park (2008). Male genitalia (Figs 2-7). Median lobe of aedeagus with short and bent basal part and long apical part, apex pointed and curved down in lateral view, internal sac with field of numerous sclerotized scales, situated medially and subapically lengthwise (Figs 2-3), blade long, with margins regularly narrowed towards pointed apex in dorsal view (Fig. 4); right paramere elongate, with short triangular, basal process extended inwardly (Figs 5-6), left paramere conchoid, with massive vermiform, basal process inwardly (Fig. 7).

Etymology.

A noun in the genitive case. Honours Kippling Will, a notable American carabidologist, for his studies on the Pterostichitae carabids.

Distribution.

So far, this species was only found in two caves in the southern part of Java Island, Indonesia (Fig. 8): cave Seplawan near village Donorejo (Central Java Province, Purworejo Regency, Kaligesing District); cave Ngingrong near village Mulo (Yogiakarta Special Administrative Region, Gunung Kidul Regency).

Affinities.

Due to the present knowledge of the taxonomy of the genus and its related taxa, it is difficult to identify the adelphotaxon of the new taxon or to state the most related taxa to it, moreover some unnamed species (see Will and Park 2008: 189-190, Fig. 1) await adequate examination. Based on selected features, namely moderately large size of body, slightly iridescent tegument, sides of pronotum convex posteriorly, with lateral fields broadened and moderately reflexed towards the base, prosternum shallowly sulcate medially near apex, apex of elytra without evident spines, Metabacetus willi sp. n. seems closer to Metabacetus laotinus Straneo, 1938 (Laos) and Metabacetus immarginatus s.l. (India: West Bengal and North Burma) than to the other congeners. However, the species from South Java well differs from the last two species in the presence of more elongate appendages (especially long maxillary palpi), segments IX-XI of antennae reaching beyond the base of pronotum, pronotum widest after the middle, with anterior margin much shorter than posterior one, sides much narrower anteriorly than posteriorly, and obtuse hind angles.

Ecological remarks.

Metabacetus willi sp. n. is the first member of the genus which can be classified as trogloxene (or troglophile). Although slight, it shows several morphological adaptations to cave-dwelling. Compared with the other congeners, its eyes are less protruding, with ommatidia less numerous, its appendages (namely, the maxillary palpi, antennomeres, and legs) a bit longer, and body less robust in sagittal plan and more flattened along the dorsoventral axis. However, the flight wings of the new species are still well-developed and it seems capable of flight. Most probably, this beetle lives not only in caves, but also on the forest floor of woodlands outside the cave systems.

Another related species, Mateuellus troglobioticus (Fig. 9), which together with Metabacetus belongs to the same clade ( Will 2006, Will and Park 2008: 190), displays predominant trilobite mode of life. For the time being, this form has been found three times in caves only ( Deuve 1990, present paper).