Michyrus Skelley and Gasca-Álvarez, 2020

Skelley, Paul E. & Gasca-Álvarez, Héctor Jaime, 2020, Michyrus, a new genus of pleasing fungus beetles with coarsely faceted eyes (Coleoptera: Erotylidae), Insecta Mundi 2020 (836), pp. 1-8 : 2-3

Michyrus Skelley and Gasca-Álvarez , new genus

Type species. Michyrus thomasi Skelley and Gasca-Álvarez , new species, present designation.

Diagnosis. Michyrus is a genus of Neotropical Tritomini characterized by having a robust body, large coarsely faceted eyes, emarginate anterior clypeal margin, mentum with plate pentagonal, undilated tibiae, compact antennal club with a short hemispherical antennomere IX, pronotum with marginal bead posteriorly behind group of large punctures at each side, and elytra lacking a marginal bead at the base.

Description. Length 6.9–8.3 mm. Body shape elongate-elliptical, weakly parallel-sided, convex dorsally; surface microreticulation weak, surface dull or glossy; unicolorous dark brown to black, lighter maculations present on elytral humeral angles and apex, appendages lighter brown.

Head with ocular striae ending at or before anterior angle of eye; frons with an impression near base of antennae; epistome wedge-shaped (i.e. with antennal insertions more lateral, not readily visible anteriorly), with weakly concave apex, lacking marginal bead; epistome punctures denser and larger than punctures on vertex. Eye large, bulging from side; facets coarse. Antenna short, reaching middle of pronotum; antennomere I large, elongate; antennomere II circular, ball-like, length = 0.5× antennomere I; antennomere III elongate, length equal to next 2 antennomeres combined; antennomeres IV to VIII length subequal to width, apically rounded; antennomeres IX–XI form a compact club; antennomeres IX–XI equal length and 3× width of antennomere VIII; antennomere IX–X hemispherical, with weakly concave apex; antennomere XI transversely elongate-oval, symmetrical. Maxilla with terminal palpomere securiform, slightly elongated laterally, width = 1 to 2× length. Labium with terminal palpomere elongate, elliptical, length = 1.5× width. Mentum with carinal lined plate pentagonal, sides equal to basal width; medial ridge extension carinate. Subgenal braces present, lateral edge broadly rounded, forming inner side of groove next to the eye for reception of antennomeres.

Pronotum with disc evenly rounded; sides arched inwardly toward eyes; anterior angles closer together than posterior angles; anterior edge lacking marginal bead between eyes; anterior angles forwardly produced, making anterior edge concave; base sinuate, lobed at middle, marginal bead present behind group of large punctures at each side; disc with evenly scattered puncture. Scutellar shield pentagonal, wider than long. Elytra with sides parabolically rounded to apex; lacking with marginal bead at base; 7 striae evident by rows of punctures, lacking at humerus and extreme apex; intervals flattened, with minute punctures; elytral epipleuron widest at base, narrowing at hind coxae, gradually folding under to apex.

Prosternum weakly keeled, with complete anterior marginal bead and strongly constricted (pinched); sternal plate triangular-trapezoidal; coxal lines anteriorly converging, barely surpassing front of procoxa, lines not continuous around coxae, line anterior to coxa broad, groove-like; posterior edge of prosternal process slightly concave, with weak marginal bead. Mesoventrite coxal lines parallel, straight, short, width between mesocoxae 4 times length of line; plate transversely rectangular; posteriorly truncate. Metaventrite lines extending onto disc from inside of mesocoxa toward posterior angle of metaventrite not continuous around mesocoxae, length a third distance to posterior angle; line behind mesocoxae strongly impressed.

Legs with femora slightly swollen, posterior margin sharp with weak marginal bead; protibia weakly curved; meso- and metatibae almost straight, gradually widening to weakly dilated apex; tarsi pseudotetramerous.

The first visible abdominal ventrite with coxal lines present or absent, continuous around metacoxae or not. Male genitalia unknown, all available specimens are female. Female genitalia with straps appendant to abdominal segment VIII; abdominal segment IX elastic, length variable; flattened plate-like proctigeral lobe; gonocoxite with slender gonostylus ( Fig. 9–10 ). Proportions of these structures vary little throughout the genus. Spermatheca sclerotized, head oval, narrow. Stridulatory files not present on base of female heads. Sexual dimorphism unknown.

Etymology. The genus name, Michyrus , is for Dr. Michael C. Thomas, a friend and mentor. The name is based on the linking of his first name “ Mich- ” and the suffix “- yrus ” from the name Ischyrus (Gender masculine).

Remarks. None of the available specimens is male, making it impossible to describe male genitalia, speculate on sexual dimorphisms, or confidently discuss potential relationships. Michyrus has coarsely faceted eyes, but falls outside of the Ischyrus - Megischyrus complex ( Skelley 2020b) and is one of the “new genera” with pentagonal mentum mentioned in couplet 1 of Skelley (2020b). However, the pentagonal mentum, curved protibiae, and concave anterior clypeal margin, in some ways, are similar to those seen in Pselaphacus Percheron, 1838 . Other characters, like their smaller body size, more robust body shape, compact antennal club, and prosternal development, are like those seen in Lybas Lacordaire, 1842 , or Myceporthus Skelley and Powell, 2018 , which have triangular to weakly pentagonal mentum and finely faceted eyes. Male specimens and a full phylogenetic analysis are needed to help resolve the relationship questions which are outside the scope and necessity of this paper. Only after a majority of these strange genera of Tritomini are described can a meaningful analysis be made.

Figures

Figures 6–10. Miscellaneous structures. 6–8) Michyrus thomasi Skelley and Gasca-Álvarez, holotype female. 6) Head and prothorax, ventral view. 7) Antenna, ventral view. 8) Abdomen, ventral view. 9–10) Female genitalia. 9) Michyrus thomasi Skelley and Gasca-Álvarez, paratype. 10) Michyrus yvineci Skelley and Gasca-Álvarez, holotype. Photographs 6–9 by PES, 10 courtesy Jean-hervé Yvinec.