Microsternus tricolor Lewis 1887

Microsternus tricolor is a species of pleasing fungus beetle in the family Erotylidae. It is endemic to China, Taiwan, Russia and Japan.

The species' name comes from Greek and Latin, "tricolor" meaning "three colors".

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.

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