Microsternus tricolor Lewis, 1887

Dai, Cong-Chao & Zhao, Mei-Jun, 2013, Genus Microsternus Lewis (1887) from China, with description of a new genus Neosternus from Asia (Coleoptera, Erotylidae, Dacnini), ZooKeys 340, pp. 79-106 : 89-92

Microsternus tricolor Lewis, 1887 Figs 22-23, 24-29, 30-33, 41, 46, 51, 61-62, 73, 77

Microsternus tricolor taiwanicus Nakane, 1966, syn. n.

Material examined.

CHINA: Hainan Prov.: 1♂♂, 1♀, Shangsi County, Mt. Wuzhishan, 18°54'N, 109°41'E, alt. 800-1000 m, 22.IV.2011, Bi Wenxuan leg. (CBWX); 1♂, Jianfenglin N R. Mingfenggu Valley, 18°44'N, 108°50'E, alt. 1000 m, 22. V.2011, Bi Wenxuan leg. (CBWX)

Description.

Body (Figs 22-23, 73, 77) elongate, length: 3.0-5.0 mm; width: 1.4-2.4 mm. Body red to reddish-brown. Each elytron orange and black spots or bands.

Head width between eyes = 8 times eye diameter in dorsal view; punctation coarse, close, separated by half to two puncture diameters; epistome truncate, lacking marginal line on anterior margin; stridulatory files not evident. Eyes coarsely facetted. Antennomere III about 1.7 times as long as IV; antennomere VIII slightly wider than VII, about 1.2 times as wide as long; antennomere IX trapezoidal; antennomere X transverse; antennomere XI almost elliptic. Gular area with pit posterior to the postmandibular lobes (Fig. 41). Maxillary and labial terminal palpomeres acuminate, sensory area restricted to apex. Mentum broad with anterior projection, almost triangular, slightly more than 4.0 times wider than long.

Pronotum (Fig. 46) arched, widest at base (pl/pw = 0.58); narrowed from base to apex, with formed thinned lines in lateral view (Fig. 51); disk coarsely and close punctured, except the impunctate medio-basal area, which is limited by an arched transverse row of coarse punctures.

Prosternum with median area including its process elevated in an elongate triangular plane, which is distinctly bordered by a ridge on both sides and shortly rounded-subtruncate in front, bearing a few fine punctures; sides rugose, coarsely and densely punctured. Mesosternum almost conceled by prosternal process, impunctate as the mesepisterna, which is somewhat concave. Metasternum rather sparsely and strongly punctured on lateral areas, some finer punctures on median area, with a pair of mesocoxal lines strongly divergent posteriorly. Abdomen rather strongly and closely punctured, but median areas of four basal visible sternites and medio-basal area of last visible sternite with few punctures respectively; without metacoxal lines on basal visible sternite. Legs rather robust.

Scutellum pentagonal, with each corner rounded, flattish and almost impunctate on surface.

Elytra convex, with eight striae of distinct punctures on each elytron and each interstice with a row of extremely fine punctures.

Male genitalia (Figs 24-25) with flagellum bearing a straight mass on apical quarter; flagellar (Figs 61-62) apex acute with a well-separated ventral process; dorsal lobe of internal sac with spade -like structure in dorsal view (Figs 26-27).

Female genitalia (Fig. 28) and spermatheca (Fig. 29) simple.

Distribution.

China, Japan, Russia (Far East), Oriental region.

Diagnosis.

Microsternus tricolor is characterized by its close punctured pronotum, orange and black interphased bands of elytra (Figs 30-33) and dorsal lobe’s unique structure of internal sac.

Comment.

Nakane described ‘taiwanicus’ for a single female specimen, according his description, Microsternus tricolor taiwanicus can be distinguished from Microsternus tricolor by a difference in the elytral bands: Microsternus tricolor taiwanicus has the median black patch on each side is nearly quadrate, not triangular and more extended inwards, with the inner margin more longitudinal and the front angle nearly rectangular; the posterior yellow fascia is much broader and nearly as wide as the black band before the apex. On studying the specimens of Microsternus tricolor , we find the bands of elytra are variable in different specimens (Figs 30-33), after compare the photos about Microsternus tricolor from Taiwan and Japan, we think the differences Nakane mentioned in his paper are not unique to Taiwan.

Based on the information outlined above, we considered Microsternus tricolor taiwanicus is a new synonym of Microsternus tricolor .