Arhytinus timorensis, Baehr & Reid, 2017

Baehr, Martin & Reid, Chris A. M., 2017, On a Collection of Carabidae from Timor Leste, with Descriptions of Nine New Species (Insecta: Coleoptera, Carabidae), Records of the Australian Museum 69 (6), pp. 421-450 : 430-432

Arhytinus timorensis sp. nov. Baehr

Figs 4 , 20

Holotype ♀, “ TIMOR LESTE gorge 1k NE Laclubar 8°44'47"S 125°54'54"E E. uro /siamweed above gorge, at mv light 1030m 3.vi.2012 C. Reid TL2012/107/598” K402689 ( AMS).

Etymology. The name refers to the occurrence of this species on the island of Timor.

Diagnosis. Moderately large species (in genus), distinguished from all species recorded from adjacent areas (eastern Java, Bali, Sulawesi, Moluccas, New Guinea) and of similar body size, except A. brendelli Baehr & Schmidt, 2010 from Sulawesi, by decidedly shorter and wider elytra. From the latter species distinguished by slightly larger body size and considerably narrower pronotum with narrower base.

Description. Measurements. Body length: 5.5 mm; width: 2.65 mm. Ratios. Width/length of pronotum: 1.52; width of widest diameter/base of pronotum: 1.24; width base/apex of pronotum: 1.06; width pronotum/head: 1.31; length/width of elytra: 1.32.

Colour ( Fig. 4 ). Black, dorsal surface rather iridescent. Lateral margins of pronotum and elytra indistinctly and very narrowly dark red. Labrum and mandibles dark red, palpi and antenna pale red, though 2nd and 3rd antennomeres slightly darker. Femora bright yellow, tibiae and tarsi slightly darker.

Head ( Fig. 4 ). Comparatively large. Eye large, laterally well projected but not semicircular, orbit short, oblique. Frontal furrows shallow, irregularly circular, developed only immediately behind clypeal suture. Antenna moderately elongate, just slightly surpassing the base of the pronotum, 6th antennomere c. 1.5 × as long as wide. Surface with fine, verY slightlY superficial, isodiametric microreticulation which is weaker towards the neck, rather glossy and iridescent.

Pronotum ( Fig. 4 ). Rather wide, widest slightly in front of middle, dorsal surface rather depressed. Apex fairly deeply excised, apical angles projected but widely rounded. Lateral border evenly convex to close to base, immediately near the basal angle very faintly sinuate. Base rather wide in comparison with diameter, slightly convex. Basal angles obtusely dentate, laterally very faintly projected, c. 120°. Lateral margin anteriorly narrow, in basal fourth widened and deplanate. Apex finelY margined, base in middle not margined. Median line shallow but distinct, not attaining apex and base. Both transverse impressions very shallow. Basal grooves wide, shallow. Anterior lateral seta inserted at apical third, slightly in front of widest diameter, and slightly removed from margin. Posterior lateral seta inserted slightly in front of the basal angle. Posterior third of lateral margin and base behind the posterior transverse sulcus with coarse, moderately dense, irregularly spaced punctures. Surface with extremelY fine and rather superficial, verY transverse microreticulation which is composed of dense transverse meshes and lines, surface glossy and distinctly iridescent.

Elytra. Of average shape, comparatively short and wide, slightly oviform, dorsal surface moderately convex and slightly depressed on disk. Humeral area comparatively wide, lateral margins in basal half but very slightly convex, then evenly convex. Striae deeply impressed, barely crenulate, intervals distinctly raised, convex throughout. 3rd interval impunctate. OnlY extremelY fine and extremelY superficial traces of microreticulation recognizable at very high magnification, composed of finest transverse lines. Surface very glossy, with distinct iridescent lustre.

Lower surface. Prosternal process apparently without seta at apex . Proepisternum with verY fine, rather superficial though distinct microreticulation that consists of very transverse meshes, rest of lower surface without perceptible microreticulation. Middle of terminal sternum with very short, erect pilosity. Metepisternum fairly elongate, c. 1.5 × as long as wide at anterior margin. Terminal sternum in female quadrisetose.

Male genitalia. Unknown.

Female gonocoxites ( Fig. 20 ). Gonocoxite 1 short and stout, with 5–6 stout, at apex acute ensiform setae at the apical rim of the ventral surface; gonocoxite 2 curved, with rather acute apex, with one short dorso-median ensiform seta at middle, three elongate, stout ventro-lateral ensiform setae, and a single short preapical nematiform seta originating from a pit. Lateral plate with several small setae at the apical margin.

Variation. Unknown.

Distribution. Western part of Timor Leste. Recorded only from the type locality.

Collecting circumstances. Sampled at light in tall Eucalyptus woodland with siamweed, near a gorge, at median altitude.

Relationships. Without knowledge of the male genitalia, relationships in the genus Arhytinus are difficult to determine, because of the high grade of similarity in body shape and surface structure in most species. However, in view of body size, overall shape, and length of elytra, the most similar species recorded from surrounding areas seems to be A. brendelli Baehr & Schmidt, 2010 from Sulawesi.

Remarks. The new species represents the first record of the genus Arhytinus from Timor. However, as explained in the introduction, specimens of Arhytinus are so rarely and sporadically sampled that it would be premature to speculate about presence, or absence, of the genus in areas, or on islands, from where it was not yet recorded. Hence, certainlY the new species fills a gap in the genus’ range, but this is not too surprising.

Although the holotype of the new species is a female, comparisons of body size and shape with all species that occur in surrounding areas clearly demonstrates, that it is different from all described species. Nevertheless, males would be useful to corroborate the taxonomic decision.

It is uncertain whether the apparently very restricted ranges of most species of the genus Arhytinus are due to the extremelY sparse material and the apparent difficulties in sampling these species, or whether they match the actual distribution patterns. Very few species, particularly those from islands in the Indonesian and Philippine insular belts, have been recorded from more than one locality, or one island. Because most Arhytinus species , as far as it has been recorded, have been sampled in more or less dense forest, the ranges indeed may be restricted, because such forest types favor the development of restricted ranges, or, vice versa, impede the vagility of those forest species.

Since the holotype is a female, the relationships of the new species so far are uncertain, because the complexly structured and verY different male genitalia offer the best tool for species differentiation and probablY also for the determination of relationships.

Although several species of Arhytinus occur in New Guinea and one on each of New Britain and New Ireland, the genus is an Oriental faunal element which is not only demonstrated by its apparent absence from Australia, but, more importantly, because the presumably most basal species, in terms of their phylogenetical status, occur in mainland Asia and in the northern part of the Indonesian Archipelago (Baehr, 2010).

Identification

When using the key to species of Arhytinus in Baehr (2012), couplet 27 is easilY reached, but must be modified as follows:

27 Elytra shorter, ratio length/width 1.32; base of pronotum narrower as compared with apex, ratio base/ apex 1.06; also pronotum narrower, ratio width/length 1.52. Timor ............................ A. timorensis sp. nov.

—— Elytra longer, ratio length/width>1.40; base of pronotum wider as compared with apex, ratio base/ apex>1.10; also pronotum usually wider, ratio width/length>1.52, usually much more. Southern India, Sikkim, Burma, Thailand, Vietnam, China, Philippines, Sumatra, Java ........................... couplet 27 of Baehr’s (2012) key.

Although A. timorensis keys out with A. bembidioides Bates, 1889 , A. indicus Baehr, 2010 , A. gerdi Baehr & Schmidt, 2010 , and A. darlingtoni Baehr, 2012 , it is most similar in body shape, particularly in the very short elytra, to A. brendelli Baehr & Schmidt, 2010 , from Sulawesi. However, this latter species is smaller and has a decidedly wider pronotum.

Colpodes truncatellus Fairmaire, 1881 .— 25 ex. “Kablaki Hotel, Same 8°59'60"S 125°38'53"E at mv light opposite field

490m 26.v.2012 D.Britton TL2012/082/548” K402572–574, K402588–596 (AMS); “Mt Laritame 8.69178S 126.38719E water tank, edge moss forest, 1150m TL2012/011/030 b/ light bucket trap 31.v.2012 ” K402575, K402577–579, K402586, K402598 (AMS), 1 K402581 (CBM); “Hatoudo 8°58'55"S 125°37'27"E, riverine rainforest, 735m 26.v.2012 C. Reid TL2012/088/546 mv light sheet” K402576 (AMS); “Bobanaro 9°01'47.6'S 125°29'29.1'E at light, hotel balcony 835m 26.xi.2011 V. Kessner, Z. Afranio TL169/11” K402583 (AMS); “c 1k N Maubisse c8:50'00"S 125:35'46"E at light, cafe verandah c. 1400m. 30.xi.2011 V. Kessner, Z. Afranio” K402584 (AMS); “Mt Laritame, Water Tank 5; - 8.69178S; 126.38719E; 31 May 2012; 1150m; edge of moss forest; D.J.Bickel, A.Mitchell, J.R.Weiner, V.Kessner, A.V.Ribeiro;TL2012/011/016 [black light bucket trap]” K402587 (AMS). Colpodes (s. l.) Macleay, 1825 is a genus of convenience, that urgently needs a revision, not only at the specific, but also at generic level. In the Oriental Region there is a multitude of undescribed species. Colpodes truncatellus (usually under the name C. habilis Sloane, 1907 ) is a common species in New Guinea and surroundings.

Colpodes obscuritarsis Chaudoir, 1879 .— 3 ex. “Bobonaro 9:01'47.6"S 125:19'29.1"E at light, hotel balcony 835m 28.xi.2011 V. Kessner Z. Afranio TL 169/11” K402676 ( AMS); “2.7k N Aileu 8°42'28"S 125°33'46"E coffee/ Paraserianthes 950m 1.vi.2012 C. Reid TL2012/101/587 sweeping” K402675 ( AMS); “1k SSW Maubisse, R. Sara, Same Rd 8°50'25"S 125°35'36"E coffee/casuarina 1360m 1.vi.2012 C. Reid swept LT2012/099/585” K402674 ( AMS). A widespread species in the Indonesian Archipelago .

Colpodes nr. saphyrinus Chaudoir, 1879 .— 1 ex. ”Mt Laritame 8.69178S 126.38719E water tank, edge moss forest, 1150m TL2012/011/030 b/ light bucket trap 31.v.2012 ” K402600 ( AMS). The single specimen is fairly similar to C. saphyrinus , a species widely distributed in the Oriental Region. Several similar, apparently undescribed, species are known from the Oriental Region, therefore the determination is doubtful .

Colpodes sp. 1 — 1 ex. “ Mt Laritame 8.69178S 126.38719E water tank, edge moss forest, 1150m TL2012/011/030 yellow pans 30.v.2012 ” K402599 ( AMS). An additional, presently indeterminate, probably undescribed species of the genus Colpodes s.l .

Colpodes sp. 2 — 1 ex. “Bobonaro 9°01'47.6"S 125°19'29.1"E at light, hotel balcony, 835m 26.xi.2011 V. Kessner, Z.Afranio TL169/11” K402585 ( AMS).Another indeterminate, probably undescribed species of the genus Colpodes s.l .

Dicranoncus queenslandicus (Sloane, 1903) .— 3 ex. “Mt Laritame 8.69178°S 126.38719°E water tank, edge moss forest, 1150m TL2012/011/016 b/ light bucket trap 31.v.2012 ” K402681–682 ( AMS); “Mt Laritame 8.69178°S 126.38719°E water tank, edge moss forest, 1150m TL2012/011/016 mv bucket trap 31.v.2012 ” K402680 ( AMS). This species is newly recorded from Timor and was previously only known from northern Australia .

Euplynes cyanipennis Schmidt-Goebel, 1846 .— 1 ex. “Hatoudo 8°58'55"S 125°37'27"E, riverine rainforest, 735m 27.v.2012 C. Reid TL2012/088/562” mv lamp, K402677 ( AMS). A widespread species in the southern Oriental Region .

Figures

Figure 4. Arhytinus timorensis sp. nov., head and prothorax.

Figures 18–22. Female gonocoxites 1 and 2. (18) Mecyclothorax timorensis sp. nov. (scale 0.1 mm). (19) Rhytisternus externus sp. nov. (scale 0.5 mm). (20) Arhytinus timorensis sp. nov. (scale 0.25 mm). (21) Notagonum reidi sp. nov. (scale 0.25 mm). (22) Aristolebia timorensis sp. nov. (scale 0.5 mm).