Microrhagus lecontei 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 : 19

Microrhagus lecontei Otto , new species

Adults

( Fig. 57–60 )

Diagnosis. Within the species group, shorter antennomere IV in relation to antennomere V ( Fig. 7 ) will distinguish M. lecontei from M. triangularis . Whereas, M. triangularis is distinguished by antennomere IV being as long as V ( Fig. 8 ).

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, tibiae and tarsi dark brown; head, pronotum and elytra clothed with short, yellow recumbent setae, more apparent on pronotal base and basal third of elytra ( Fig. 57 ).

Head: Closely punctate, subspherical with convex frons; surface shiny; apical margin of frontoclypeal 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; antennomere IV slightly shorter than V; antennomere V slightly shorter than VI; antennomeres VI–X each triangular, subequal and longer than wide; antennomere XI longer than X.

Pronotum: Evenly, shallowly punctate; surface shiny; as long as wide, with moderate hind angles; lateral sides parallel-sided; arcuate anteriorly; disc simple, without median impressions; base sinuous, with elongate, median carina above scutellum, deeply impressed on both sides of the carina; sides ( Fig. 58 ) 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, slightly oblong, triangular, and distally rounded.

Elytra: Indistinctly striate; interstices flattened; surfaces evenly punctate.

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 tarsomere IV truncate and excavated; metathoracic tarsomere V elongate with simple claws.

Venter ( Fig. 59 ): Punctate, with recumbent whitish setae; hypomeron with notosternal antennal grooves; metathoracic episternum caudally widened; metathoracic coxal plates medially 2.5 times as wide as laterally.

Male aedeagus ( Fig. 60 ): Basal piece oblong, narrow, rectangular, nearly as long as remaining aedeagus; remaining aedeagus short, narrow, as wide as basal piece; lateral lobes short, simple, apically narrowed; secondary lateral lobes fused with lateral lobes; median lobe delicate, inconspicuous.

Female allotype: Length 3.5 mm; antennae weakly serrate, reaching two-thirds the length of the body; antennomere IV distinctly shorter than V; femur dark brown, tibiae and tarsi medium brown; pedicel and scape slightly darker; basal impressions on both sides of median carina shallower.

Variation. Twenty-four adult paratypes were examined. Seventeen male paratypes varied in length from 2.5–3.25 mm. Seven female paratypes varied in lengths from 2.5–3.5 mm. Females are slightly larger than males. Female antennae are generally weakly serrate, stouter with antennomeres VI–X slightly longer than wide. Antennomeres IV and V each distinctly shorter than remaining antennal segments in females. Some male paratypes have lighter colored antennae than the holotype. Darker brown colored femora are present in some male paratypes. In those same specimens, tibiae and tarsi are medium brown in color. A few males have a uniformed light medium brown coloration, perhaps owing to their slightly teneral state at time of collection. In both sexes, most specimens have a posterior lateral pronotal ridge consistent with the holotype, extending up to three-fourths the length of the pronotum. Only a few specimens however, have a shorter posterior lateral pronotal ridge, extending up to half the length of the pronotum. The anterior lateral pronotal ridge in some female paratypes is oblique and flatter, lacking that archness as it extends downward, compared with the male paratypes. Some degree of variation is present at the basal pronotal median carina above the scutellum. The median carina ranges from being weaker in some specimens to more pronounced in other specimens. The basal median carina is shorter in some specimens. The pronotal base showed some impression variations at both sides of the median carina. Some specimens have deeper impressions at the base than other specimens in the series.

Figures

Figures 57–60. Microrhagus lecontei Otto. 57) Holotype, dorsal view. 58) Holotype, lateral view. 59) Holotype, ventral view. 60) Aedeagus of paratype. Scale line = 2.0 mm.

Figures 3–8. Nearctic Microrhagus. 3) Microrhagus audax, pronotum, lateral side. 4) Microrhagus carinicollis, pronotum, pronotal hind angles circled. 5) Microrhagus brunneus, pronotum, pronotal hind angles circled. 6) Microrhagus carinicollis, vertex. 7) Microrhagus lecontei, antennomeres 3–6. 8) Microrhagus triangularis, antennomeres 3–6.