Holotrochus hamatus, Irmler, 2013

Irmler, Ulrich, 2013, New species of the genus Mimogonia and Holotrochus from South America (Coleoptera: Staphylindae: Osoriinae), Acta Entomologica Musei Nationalis Pragae 53 (1), pp. 155-176 : 166-167

Holotrochus hamatus sp. nov.

( Figs 11 , 18C )

Type locality. Paraguay, Puerto Presidente Stroessner .

Type material. HOLOTYPE:, ‘ Paraguay, Puerto Presidente Stroessner (54°36’ W, 25°31’ S), Hungarian Soil-Zool. Exp., 06.01.1966, leg. L.S. Mahunka’ ( HNHM).

Diagnosis. This species certainly belongs to the H. simplex group due to the size, existence of a margined front edge of pronotum, and the absence of abdominal pubescence. Holotrochus hamatus is characterised by its short antennae with the fourth antennomere wider than long and the pronotum widest in the middle. Similarly short antennae are found in H. blackwelderi Irmler, 1981 , but total size of the body is distinctly smaller. Among the most other similarly sized species of the group, the pronotum is widest in the apical third. In this respect H. hamatus resembles H. vianai Bernhauer, 1939 within the species found from the same region, but the structure of the endophallus differs significantly. In contrast to H. hamatus , the endophallus of H. vianai , is simply spiralled with a row of short apical teeth.

Description. Length: 4.2 mm. Colouration black, elytra slightly lighter, brown; fine posterior margin of pronotum reddish; legs and antennae red.

Head 0.65 mm long, 0.81 mm wide; eyes not prominent; temples nearly twice as long as eyes; with fine supraocular margin continuing to base of antennae; 4 setiferous punctures within the margin; front edge with several setiferous punctures; on a line between posterior edge of eyes with row of four setiferous punctures; interstices between inner punctures twice as wide as interstices between inner punctures and outer punctures; irregular punctation on vertex distinct; on average, distance between punctures distinctly wider than diameter of punctures; without microsculpture on vertex, but with sparse and fine micro-punctation; surface polished and shiny.

Antennae short, only slightly longer than head; second antennomere globular and only half as long as conical third; fourth antennomere again wider than long; following antennomeres slightly increasing in width; tenth antennomere twice as wide as long.

Pronotum 0.38 mm long, 0.84 mm wide; widest in the middle; in posterior half only slightly narrowed, nearly parallel; in anterior half more distinctly narrowed; sides margined; margin continuing to anterior edge; in dorsal aspect, lateral margin partly hidden in anterior half; punctation similar as on head, but punctures posteriad increasing in size; irregular punctation on anterior half as dense as on head, on posterior half slightly denser; on average, interstices between punctures slightly shorter than diameter of punctures; with impunctate midline in posterior half; with very weak remains of microsculpture, but with sparse micro-punctation; surface shiny.

Elytra 1.07 mm long, 1.14 mm wide; shoulders distinct, nearly rectangular and with very short teeth; punctation coarse and moderately dense; in size and density, punctation similar to punctation of posterior pronotum; ground-sculpture coarse and coriaceous; surface less shiny than on head and pronotum.

Abdomen with very fine punctation; punctures almost half as large as punctures on head or pronotum; surface with distinct net-like microsculpture; surface less shiny than head and pronotum; last sternite widely rounded at apex, with numerous net-like striae and pair of groups of fine punctures.

Aedeagus with shortly curved apical part and obtuse apex; parameres shorter than apical part of central lobe; endophallus bilobed; dorsal lobe with row of four teeth.

Etymology. The specific name hamatus (Latin, adjective) means “hook-like”.

Distribution. Known only from the type locality

Figures

Figs 8–11. 8– Holotrochus yasuniensis sp. nov.; 9 – H. mrazi sp. nov.; 10 – H. paraguensis sp. nov.; 11 – H. hamatus sp. nov. Body parts:A – aedeagus; B – antenna, C – tergite XII, D – last sternite. Scale bar: 0.1 mm.

Fig. 18. Head, pronotum, and elytra of Holotrochus Erichson,1839 showing shape, punctation, and microsculpture.A – H. paraguensis sp. nov.; B – H.tortilis sp. nov.; C – H.hamatus sp. nov.; D – H.yanuniensis sp. nov.; E – H. mrazi sp. nov.; F – H. lobatus sp. nov. Scale bars: 0.5 mm.