Microrhagus carinicollis Otto, 2015

Otto, Robert L., 2015, Eucnemid larvae of the Nearctic region. Part V: Fifth instar larval descriptions for eight species of Microrhagus Dejean, 1833 (Coleoptera: Eucnemidae: Melasinae: Dirhagini), with descriptions of four new species and notes on their biology, Insecta Mundi 2015 (421), pp. 1-46 : 15-16

Microrhagus carinicollis Otto , new species

Adults

( Fig. 48–51 )

Description. Male holotype: Length, 3.0 mm. Width, 1.0 mm. Body subcylindrical, moderately elongate and tapering towards the elytral apex; uniformly black; antennae dark brown, except pedicel and scape reddish; femur dark brown; tibiae and tarsi reddish-brown; head, pronotum and elytra clothed with short, yellow recumbent setae ( Fig. 48 ).

Head: Very closely punctate, subspherical with convex frons; vertex with slightly elevated short median carina; surface somewhat shiny; apical margin of frontolclypeal region feebly trilobed, about 2.5 times wider than base; mandibles stout, bidentate, densely punctate.

Antennae: Moderately serrate from antennomeres IV–X, reaching about three-fourths the length of the body, setose. Antennomere III longer than IV; antennomeres IV–X each triangular, subequal and longer than wide; antennomere XI longer than X.

Pronotum: Closely, shallowly punctate to almost rugose; surface shiny; slightly longer than wide, with moderate hind angles; lateral sides sub-parallel-sided, apically widened; arcuate anteriorly; disc simple, without median impressions; base sinuous, with short, median carina above scutellum, slightly impressed on both sides of the median carina; sides ( Fig. 49 ) with two lateral ridges; anterior lateral hypomeral ridge short, obliquely bent, less than one-fourth the length of pronotum; posterior lateral hypomeral ridge extending up to three-fourths the length of pronotum.

Scutellum: Punctate to rugose, slightly oblong, triangular, and distally rounded.

Elytra: Very weakly striate; interstices slightly elevated; surfaces closely punctate to rugose.

Legs: First tarsomere longer than the combined lengths of the remaining four on mesothoracic and metathoracic tarsi; tibiae rounded in cross section; lateral surfaces of mesothoracic and metathoracic tibiae with single spines; metathoracic tarsomeres I–III simple; metathoracic tarsomeres IV truncate and excavated; metathoracic tarsomere V elongate with simple claws.

Venter ( Fig. 50 ): Punctate, with recumbent yellowish setae; hypomeron with notosternal antennal grooves; metathoracic episternum caudally widened; metathoracic coxal plates medially 2.5 times as wide as laterally.

Male aedeagus ( Fig. 51 ): Basal piece oblong, somewhat elliptical; remaining aedeagus a little more than twice as long as basal piece, basally narrowed, apical three-fourths widened; lateral lobes short, simple, apically narrowed; secondary lateral lobes fused with lateral lobes; median lobe widened, elongate, apically bilobed.

Female allotype: 3.5 mm long; antennae dark brown, weakly serrate, reaching almost two-thirds the length of the body; legs and antennae slightly darker.

Variation. One hundred thirty-five adult paratypes were examined. One hundred male paratypes varied in lengths from 2.75–3.75 mm. Thirty-five female paratypes varied in lengths from 3.0– 3.5 mm. Females are on average slightly larger than males. Female antennae are weakly serrate and stouter, with antennomeres VI–X slightly longer than wide. Female antennae reach almost two-thirds the length of its body. Some paratypes have lighter colored antennae compared with the holotype, perhaps attributed to their slightly teneral state at the time of collection. Some paratypes have a more consistent reddish-brown coloration of the femur, tibiae and tarsi. Posterior lateral pronotal ridge in both sexes are consistent with the holotype, extending up to three-fourth the length of the pronotum. Pronotal basal median carina above the scutellum shows some degree of structural variation and overall lengths. Some specimens have weaker carina, while others have a more pronounced basal carina. Basal median carina is shorter in some specimens. Base of the pronotum showed some variations in the depth of impressions at both sides of the median carina. Some specimens have deeper basal impressions than others. Carina at the vertex exhibits some variability. Some specimens have a shallower, finer carina; while others are almost absent. Many specimens exhibit a well-defined, short carina. Overall lengths also varied greatly among these specimens. Many specimens have a shorter carina, consistent with the holotype. Other specimens have a rather elongate carina, extending farther down the frons, just above the base of the frontoclypeal region.

Figures

Figures 48–51. Microrhagus carinicollis Otto. 48) Holotype, dorsal view. 49) Holotype, lateral view. 50) Holotype, ventral view. 51) Aedeagus of paratype. Scale line = 0.5 mm.