Agathidium (Macroceble) cornigerum, Švec, 2022

Švec, Zdeněk, 2022, Leiodidae (Coleoptera) of the Hainan Island with new faunistic records from China and with notes on the unique body modifications in the genus Agathidium, Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 62 (1), pp. 155-164 : 158-160

Agathidium (Macroceble) cornigerum sp. nov.

( Figs 5–8 , 14, 16 )

Type locality. China, Hainan Island, Limushan Mts, 19°10.5–10.9′N, 109°44–45′E, 650– 900 m.

Type material. Hඈඅඈඍඒඉൾ: J, “ China: Hainan isl. [MF 19] / Limushan Mts., mountains / above first admin. centre / 19°10.5-10.9 ′ N 109°44- 45′E / 650-900 m, 6.v.2011, Fikáček // sifting small accumula- / tions of moist leaf litter along / and on the trail in secondary / forest partly with Cyathea and / bamboo” ( NMPC). Pൺඋൺඍඒඉൾඌ: 2 JJ 5 ♀♀, same data as holotype ( NMPC, ZSPC).

Description. Length of holotype 1.6 mm, head 0.2 mm (0.5 mm including mandibular horn), pronotum 0.7 mm, elytra 0.7 mm, antenna 0.7 mm, aedeagus 0.78 mm. Maximum width of head 0.9 mm, pronotum 1.1 mm, elytra 1.1 mm. Body very shortly oval. Dorsum, antennomere 1 and legs light chestnut coloured, tarsi lighter; A2–A8

yellowish, A9–A10 brown, A11 yellow-red. Ventral surface yellow-red. Dorsum punctured, without microsculpture. Sutural striae absent; femoral lines absent, metaventrite shortened, supraocular carina low all along its length.

Head very broad, maximum width of head just before posterior margin of eyes. Eyes, feebly flattened, somewhat drop-shaped ( Fig. 16 ). Supraocular carina low with raised anterior edge of right carina forming triangular process. Subocular line not developed. Clypeus feebly roundly emarginate, clypeal line lacking. Antennomere 3 distinctly longer than A2 (A3/A2 = 1.7). Ratio of lengths of A2–A11 (A2 = 1.0): 1.0-1.7-0.9-0.9-0.7-0.9-0.9-1.4-1.1-2.6. Ratio of widths of A2–A11 (A2 = 1.0): 1.0-0.8-0.8-0.8-0.8-1.2- 1.4-2.0-2.2-2.4. Ratio of W/L of A2–A11: 0.7-0.3-0.7- 0.7-0.8-1.0-1.2-1.0-1.4-0.7. Surface of head smooth with very fine and very sparse punctures, separated by more than 10 times their own diameters. Left mandible bears long upwards oriented caudally bent horn ( Figs 14, 16 ).

Pronotum. Lateral outline broadly rounded in lateral view ( Fig. 5 ). Puncturation sparse and fine, rather similar to that on head with punctures separated by about 8–10 or even more times their own diameter.

Elytra widest at lateral angles, then distinctly narrowed posteriorly. Elytral margins straight behind lateral angles in lateral view ( Fig. 5 ). Lateral elytral channel narrow. Puncturation similar to that on head.

Legs. Tarsi slim, all tibiae slim, metafemora without specific characters. Tarsal formula: 5-5- 4 in male.

Mesoventrite. Posterior part subconcave. Anterior part raised without longitudinal carina. Lateral lines not developed.

Metaventrite. Distinctly shortened – MTW/MTLM = 3; MTW/MTLC = 6. Femoral lines missing.

Membranous wings absent.

Genitalia. Basal part of median lobe simple (type A). Apical part of median lobe narrow, elongate in long process rounded at its top in dorsal view. Operculum small, oval. Parameres flattened, triangularly widened at apex with flat oval apendices ( Figs 6, 7 ).

Variation and sexual dimorphism. Length of body 1.6– 1.9 mm in the type series. The ratio A3/A2 varies between 1.2–1.7. One of the male paratypes possesses simple left mandible without any horn, the other male paratype is with large mandibular horn as in the holotype. Tarsal formula 4-4- 4 in female. Spermatheca slim, cylindrical, S-shaped ( Fig. 8 ). Length of spermatheca 0.15 mm.

Differential diagnosis. Agathidium (Macroceble) cornigerum sp. nov. possesses greatly shortened metaventrite; femoral lines on metaventrite missing. Therefore, the new species is attributed to the subgenus Macroceble Angelini, 1993 . It is habitually similar to A. (Macroceble) pokornyi Švec, 2017 , a mountain species from Yunnan, China (Šඏൾർ 2017). Both species are similar in the shape of body, shape of head broadest at posterior part of eyes, feebly roundly emarginate clypeus, in dark antennal club with a little lighter colour of antennomere 11, both species are similar also in the length of A3 that is distinctly longer than A2. Agathidium cornigerum sp. nov. differs from A. pokornyi in lighter colouring of the dorsum, in the drop-shaped eyes that are parabola slice-shaped in A. pokornyi and mainly in the median lobe constricted before rounded tip while the tegmen is linden leaf-shaped in A. pokornyi . Also, the parameres are quite different as paramera is lacking appendix in A. pokornyi . The shape of the parameres bearing appendices is very distinctive and very specific, distinguishing the new species from the known Agathidium species except for A. apiforme sp. nov. that also possesses apical parameral appendices, but beside the shape of genitalia both species differ also in the morphological characters mentioned in the key above. Spermatheca is S-shaped in A. cornigerum sp. nov. while the same has semi-circular basal part with curved cylindrical distal part in A. pokornyi .

Etymology. The name of the new species draws the attention to the well-developed horn on the left mandible of the holotype. The name is derivate from Latin words cornum (= horn) and gere (= bear in English). Adjective.

Figures

Figs 1–8. 1, 2, 6, 7 – aedeagus laterally and tip of aedeagus dorsally. 3, 5 – lateral view of body. 4, 8 – spermatheca. 1–4 – Agathidium (Agathidium) pilulum sp. nov.; 5–8 – Agathidium (Macroceble) cornigerum sp. nov. Scale bars in Figs 1, 2, 4, 6, 7, 8 = 0.1 mm; 3, 5 = 0.5 mm.

Figs 13–16. 13, 15, 16 – head dorsally; 14 – head laterally. 13 – Agathidium (Agathidium) pilulum sp. nov.; 14, 16 – Agathidium (Macroceble) cornigerum sp. nov.; 15 – Agathidium (Macroceble) apiforme sp. nov.