Dichillus siamicus, Schawaller & Bellersheim, 2022

Schawaller, Wolfgang & Bellersheim, Aron, 2022, Two new species of the genus Dichillus Jacquelin du Val, 1861 (Coleoptera: Tenebrionidae: Stenosini) from Thailand, Zootaxa 5200 (3), pp. 296-300 : 297

Dichillus siamicus sp. n.

( Figs 1, 2, 5 )

Type material. Holotype: ♂, Thailand, Phetchaburi Province, 2 km N Ban Sa Yai Non , 12°56′58″N 99°47′44″E, 40 m, 16–18.I.2006, leg. S. Bečvář & R. Fouquè, NMPC . Paratypes. Same data as for the holotype, 8 ex. NMPC .— Thailand, Phetchaburi Province, 2 km N Ban Sa Yai Non , 12°57′23″N 99°47′57″E, 50 m, 13–16.I.2013, leg. R . Fouquè , 2 ex. NMPC .— Thailand, Phetchaburi Province, 2 km N Ban Sa Yai Non , 12°57′23″N 99°47′57″E, 50 m, 10& 14. V .2016, leg. R. Fouquè , 1 ex. NMPC .— Thailand, Phetchaburi Province, 2 km N Tha Laeng , 12°57′56″N 99°50′29″E, 25 m, 14.I.2013, leg. R . Fouquè , 1 ex. NMPC .— Thailand, Prachuap Khiri Khan Province, 4 km NW Sam Roi Yot , 12°16′01″N 99°56′56″E, 30 m, 19–20.I.2013, leg. R . Fouquè , 20 ex. NMPC .— Thailand, Prachuap Khiri Khan Province, 4 km NW Sam Roi Yot , 12°16′N 99°56′E, 10 m, 11–13. V .2016, leg. R. Fouquè , 4 ex. SMNS .— Thailand, Kanchanaburi Province, 8 km S Kanchanaburi , 13°56′21″N 99°32′46″E, 65 m, 22.I.2013, leg. R . Fouqué , 1 ex. NMPC .

Description. Body length 4.2–4.5 mm (for measurements of head, pronotum and elytra see Fig. 1 ). Body and antennae dull blackish, surface chagreened, legs dark redbrown. Head 1.1x as long as wide, widest across genae. Tempora straight conical before cervix, cervix not separated from tempora. Genae arched from posterior margin of eyes to the widest part, there straight conical to clypeus. Clypeus medially slightly excavated. Suborbital costa indistinct. Head between genae and clypeus with longitudinal impression. Eyes completely divided by genae. Dorsal punctures large, but separated, towards clypeus diminishing, without distinct setae; surface on vertex dull, on clypeus shining. Antennae short and broad, shape of antennomeres as in Fig. 1 , antennomere three 1.2x longer than antennomere two, antennomeres 1–9 with dull surface, antennomeres 10 and 11 with shining surface and with longer yellow setae. Pronotum cylindrical, 1.2–1.3x longer than wide, widest shortly before anterior angles; before anterior angles somewhat excavated, angles not protruding; posterior angles rectangular; lateral margins completely lacking, anterior and posterior margins straight. Pronotal disc medially without impression. Punctures slightly denser and larger than on vertex, but not confluent, without setae. Prosternal apophysis bent down. Elytra convex and elongate oval, widest across middle, 2.0x longer than wide, with indistinct rows of fine, sparse punctures, size of punctures smaller than on pronotum, and more separate, punctures without visible setae. All intervals flat, glabrous. Humeral angles without teeth and completely absent. Upper margin of epipleura flat, nearly invisible, epipleura with irreguar punctation ( Fig. 2 ). Legs indistinctly covered with lighter hairs. Ventrites with fine and separated punctures without setae, punctures denser on posterior ventrites, surface chagreened ( Fig. 2 ). Aedeagus ( Fig. 5 ) with basale as long as apicale, basale broader than apicale, apicale with acute apex.

Diagnosis. D. siamicus sp. n. together with D. cylindricollis Kaszab, 1975 from central India lack the lateral margins of the pronotum (see couplet 1/ 2 in the identification key of the Oriental species by Kaszab 1981). All other known Oriental species have distinct lateral margins. However, in D. cylindricollis the elytra are shorter (1.7x longer than wide), have distinct punctural rows, the head is as long as wide, and the cervix is distinctly separated from the tempora ( Kaszab 1975). For a photograph of the holotype of D. cylindricollis see http://coleocoll.nhmus.hu. The aedeagus of D. cylindricollis is unknown.

Etymology. Named after Siam, the old name of Thailand, where the type series was collected.

Remarks. Some specimens were mounted by the collector on a card together with ants, so very probably this species can be considered as myrmecophilous.

Figures

FIGURES 1–6. New Dichillus from Thailand. 1, 2, 5. D. siamicus sp. n., holotype, dorsal view (1), lateral view (2), aedeagus and spiculum gastrale (3). 3, 4, 6. D. grimmi sp. n., holotype, dorsal view (3), lateral view (4), female genitalia (6). Scale bars: 1 mm (dorsal and lateral view), 0.5 mm (genitalia).