Dichillus grimmi, 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 : 297-299

Dichillus grimmi sp. n.

( Figs 3, 4, 6 )

Type material. Holotype: ♀, 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, NMPC.

Description. Body length 3.2 mm (for measurements of head, pronotum and elytra see Fig. 3 ). Body and appendages dull redbrown, surface chagreened, elytra blackish. Head as long as wide, widest across genae. Tempora nearly parallel before cervix. Genae arched from posterior margin of eyes to the widest part, there arched and directly narrowed to clypeus. Clypeus medially excavated. Suborbital costa lacking. Head between genae and clypeus with longitudinal impression. Eyes completely divided by genae. Dorsal punctures large, on vertex slightly confluent, towards clypeus diminishing, with fine and short forward-oriented yellow setae; surface on vertex dull, on clypeus shining. Antennae short and extremely broad, shape of antennomeres as in Fig. 3 , antennomere three 1.5x longer than antennomere two, antennomeres 1–9 with dull surface, antennomeres 10 and 11 with shining surface and with longer yellow setae. Pronotum cordiform, 1.35x longer than wide, widest shortly before anterior angles, lateral margins parallel in basal third; anterior angles rounded, not protruding; posterior angles rectangular; anterior and posterior margins straight, lateral margins without distinct dentation, not beaded. Pronotal disc medially with weak longitudinal impression. Punctures dense and large as on vertex, but not confluent, with adpressed yellow setae as on head. Prosternal apophysis bent down. Elytra convex and round-oval, widest across middle, 1.3x longer than wide, with 10 rows of punctures, size of punctures similar to those on pronotum, but more separate, punctures with adjected microsetae. Alternate intervals 3, 5, 7 and 9 with weak tuberculated costae; costae with short but erect yellow setae pointing backwards. Humeral angles without teeth and completely absent. Upper margin of epipleura sharp, epipleura in posterior part with one row of punctures ( Fig. 4 ). Legs covered with fine light adherent hairs. Abdominal ventrites with small punctures with fine setae, punctures of last ventrite slightly denser and smaller, surface of last ventrite lighter than of basal ventrites ( Fig. 4 ). Aedeagus unknown, only female available. Female genitalia see Fig. 6 .

Diagnosis. D. grimmi sp. n. can be recognised among all Oriental species by the extremely broad antennae, by the convex and round elytra without humeral teeth (except in D. siamicus sp. n.), by the alternate elytral intervals with weak tuberculated costae with erect setation, and by the sharp upper margin of epipleura. In the key to the Oriental species by Kaszab (1981), D. grimmi sp. n. runs to the last couplet 27/28 ( D. chujoi Kaszab, 1966 and D. longicollis Kaszab, 1981 ). However, both species are smaller (2–2.6 mm), have longer and narrow antennae, long elongate and flat elytra without distinct setation and without costae in the intervals 3, 5 (aedeagi unknown). For a photograph of a paratype of D. chujoi see http://coleocoll.nhmus.hu. According to Kaszab (1981), all Oriental species (4) with extremely thick antennae as in D. grimmi sp. n. possess distinct humeral teeth, and are distributed more western in Pakistan, Baluchistan, Kashmir and northern India.

Etymology. Named in honour of the late Roland Grimm (1948–2021), who contibuted much to the knowledge of the tenebrionid fauna of Thailand, and in memory of our joint trip to northern Thailand in 2004.

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).