Hexagonia nigrocyanea Anichtchenko, 2022

Anichtchenko, Alexander, Sciaky, Riccardo & Medina, Milton Norman, 2022, Taxonomic notes on the genus Hexagonia Kirby, 1825 with description of three new species from the Philippines (Coleoptera: Carabidae: Hexagoniini), Baltic Journal of Coleopterology 22 (1), pp. 55-66 : 63-66

Hexagonia nigrocyanea Anichtchenko &

Sciaky sp. n.

( Figs. 6 , 11 )

Type material: Holotype, male – “ Philippines, Mindanao | Dominorog | II.2019 ” (cRS) . Paratypes: 1 female – “ Philippines, Mindanao | Bukidnon | Dominorog V.2019 ” (cRS) ; 1 male – “ Philippines, Mindanao | Sarangani | Maitum X.2017 ” (cRS) ; 1 female – “ Philippines, Mindanao | Lanao del Sur | Wao XI.2019 ” (cRS) ; 1 male – “ Philippines, Mindanao, Lanao del Sur, Wao , XI.2021 ” (cRS) ; 1 female – idem but “ X.2021 ” (cRS) ; 1 female – idem but “ IX.2021 ” (cRS) .

Diagnosis. Easily distinguishable from all known species in the Oriental region for its combination of dark bluish elytra and rather trapezoid head but without a groove connecting the fovea behind the eye with the postorbital pore, as in H. panumanod .

Description. Body length: 12,1–14,2 mm. Width/ length of head: 0.96; width/length of pronotum: 1.07; length/ width of elytra: 1.63­ 1.65. Body uniformly black, pronotum and elytra with slight bluish luster.

Head strongly trapezoid and depressed, slightly narrower than the pronotum. Eyes moderately large and markedly protruded, 0.5 times as long as temples; temples protruding; posterior border almost perpendicula. The shape of the head is slightly different in the male specimens compared to the female ones: the temples are more protruding in the males than in the females, indicating a probable sexual dimorphism in this character. Constriction of neck weak and shallow, neck

Anichtchenko A., Sciaky R., Medina M.N.

narrow. Mandibles elongate, almost straight in basal two thirds, incurved towards apex. Palpi elongate, narrowed towards apex, smooth. Mentum with wide triangular tooth, bisetose.Antenna short, attaining the lateral pore of pronotum; three basal antennomeres and basal half of antennomere 4 glabrous. Clypeal suture shallow, laterally indistinct; clypeus slightly emarginate at apex. Labrum with deep wide triangular incision, asymmetric, right lobe longer. Frons with two irregularly shaped, shallow impressions. Supraorbital pore connected by a shallow groove with the postorbital pore. Surface with extremely fine transverse microreticulation, iridescent.

of 12–13 pores. Intervals impunctate and with weak microreticulation, consisting of polygonal meshes, very glossy.

Legs of average size, tarsomere 3 of all tarsi two times shorter than basal one; tarsomere 4 wide and very deeply excised, with dense brush­like pilosity on ventral surface. Tarsal claws edentate. Pronotum wider than the head, obovate, widest at apical quarter; dorsal surface depressed. Anterior margin slightly convex, anterior angles completely rounded. Lateral margins evenly curved, immediately in front of base slightly excised; base straight, basal angles obtuse and slightly produced. Median line deep, impunctate, almost attaining anterior margin and base; both transverse sulci obsolete. Basal grooves starts right from the posterior angles in form of short, smooth, diagonal impressions. Anterior margin and base not margined, lateral borders narrowly margined, marginal gutter slightly wider near lateral pore. Anterior lateral seta situated at widest point, posterior lateral seta absent. Dorsal surface smooth, with some very shallow irregular transverse sulci, with extremely fine transverse microreticulation, slightly iridescent.

Elytra elongate, markedly depressed, parallel sided. Base oblique, humeri rounded; lateral margins straight. Basal margin straight and forming an angle at the junction with lateral margin, at position between striae 4 and 5. Scutellar stria long and connected with stria 1. All striae deeply impressed and moderately punctate. Intervals flat and smooth. Scutellar seta situated at origin of stria 1. Interval 3 with three setiferous pores: anterior one situated in the stria 3 at the level of the end of scutellar stria; median one situated in apical third of elytra near stria 2; posterior one situated close to apex, near stria 2. Interval 5 of elytra with one pore located opposite the middle between discal and apical pores. Marginal series consisting Three basal tarsomeres of all legs triangular, very wide and dorsally smooth.

Aedeagus (Fig. ??) elongate and very thin in lateral view. Apex of median lobe moderately long and slightly bent to the lower side. Endophallus with large semicircular sclerite.

Distribution. Only known from the island of Mindanao, in three different localities in the provinces of Bukidnon, Sarangani and Lanao del Sur, therefore occupying almost all the island of Mindanao. We can expect to find it in different areas of the same island.

Anichtchenko A., Sciaky R., Medina M.N.

Etymology. This specific epithet alludes to the peculiar color of this species: the Latin term nigrocyanea means, in fact, black and bluish.

Affinities. This species is the largest of the genus in the Philippines and one of the largest in the whole world. It seems related to the sympatric H. panumanod , although well distinct. As far as we know these are the only two metallic species of Hexagonia known until now.

General remarks. The genus Hexagonia in the Philippine islands seems mainly distributed in the island of Mindanao and its vicinity, in fact, four out of the five species until now known from this country have been found here, while only H. sauteri is known from the island of Luzon, beyond Taiwan, from where it had been initially described.

Darlington (1968: 203) wrote when describing Hexagonia papua : “One or more similar but apparently undescribed species occur in the Philippines.”. This sentence seems to prove that he had seen some specimens from this area belonging to the group of reddish brown species with a black spot at the elytral apex. These species are very numerous in South­East Asia, and only seeing abundant material could allow to decide whether they are new species or species known from other areas.

In any case, we think that the knowledge on this genus in the Philippines are still incomplete and that certainly some new species and new data on the species already known will be discovered as the faunistic exploration of this archipelago continues.

Figures

Fig. 6. Habitus of Hexagonia nigrocyanea sp. n. Holotype, male. Scale bar 5 mm.

Figs. 7–11. Aedeagus of Hexagonia, A – dorsal view, B – lateral view. 7 – H. andrewesi JedliËka, 1935, Holotype; 8 – H. castanea JedliËka, 1936 syn. n. Cotype; 9 – H. sauteri Dupuis, 1912, Holotype. Scale bar 1 mm. 10 – H. amicitia sp. n., Holotype; 11 – H. nigrocyanea sp. n. Holotype. Scale bar 1 mm.