Dentirotacorimus zigzag Yoshida & Hirowatari

Yoshida, Takahiro, Hirowatari, Toshiya & Hashim, Rosli, 2017, A new genus of Silvaninae (Coleoptera: Silvanidae) with two new species from the Malay Peninsula, Zootaxa 4258 (4), pp. 365-374 : 371-373

Dentirotacorimus zigzag Yoshida & Hirowatari , sp. nov.

( Figs 1 C,D, 4)

Diagnosis. This species can be distinguished from D. reticulatus by the diagnostic characters given in that species diagnosis.

Body ( Figs 1 C,D). Body length from anterior margin of clypeus to apex of elytra measured along the median line: 2.53 mm (n=1). Surface reddish brown; head and pronotum somewhat darkened; sides of elytra lighter.

Head ( Figs 1 C,D, 4A). Rounded, maximum width across eyes 0.53 mm (n=1); clypeal margin slightly reflexed; gena prominent, covering part of eye, not exceeding eye width. Eye small, protruding, directed anterolaterally, longer than combined lengths of antennomeres 3 and 4. Dorsal surface covered with short, thick and curved setae; ventrally with finer setae. Setiferous tubercles on dorsal surface relatively dense; ventral surface with punctation simple and sparser than dorsum. Antenna ( Fig. 4 A) 0.66 mm (n=1), moderately thin; antennomere 10 about 2.5× as long as 9; covered with fine setae; approximate ratios of antennomere lengths of holotype as follows: 2.0: 1.5: 1.3: 1.1: 1.0: 1.0: 1.0: 1.1: 1.1: 2.7: 1.0.

Thorax and abdomen ( Figs 1 C,D, 4B–D). Pronotum trapezoidal, widest at base, wider than long, length along median line 0.60 mm (n=1), maximum width including lateral teeth 0.62 mm (n=1); six lateral teeth, rounded at apices; anterior angle (1st tooth) gradually widened distally, directed anterolaterally; 2nd to 6th tooth triangular, 6th tooth relatively small; interstices of teeth narrow; setiferous tubercles as dense as on vertex; setae very short and thick. Thoracic ventrites with no obvious punctation apart from base of prosternum and intercoxal process of mesoventrite; mostly covered with coarse transverse microsculpture; setae short and thin; intercoxal process of procoxae gradually widened posteriorly; mesocoxal process gradually narrowed posteriorly, widened distally. Scutellar shield small, transverse, about twice as wide as long, width about 0.9× as wide as eye length, with a thin transverse furrow near base. Legs ( Fig. 4 B) covered with setae longer than those of other parts; pro- and mesocoxae rounded; metacoxa wide, with transverse ridge a little enlarged at middle, with some setae on medial areas; trochanters with extended inner distal angles, rounded at apices; femora inflated; tibiae gradually widening distally; tarsomere 5 long, more than 3× as long as 4 ( Fig. 4 C); claws simple. Abdomen 4/5 as wide as long; intercoxal process triangular; with an unbroken femoral line running along anterior margin of 1st abdominal ventrite ( Fig. 4 D); setae short and fine.

Elytra ( Fig. 1 C). Subparallel, gradually narrowed from anterior 3/7, length measured along median line 1.52 mm (n=1), maximum combined width 1.12 mm (n=1), with indistinct humeral carinae; apices rounded. Rows of punctures shallow, with small setiferous tubercles bearing short, thick and curved seta, longer than those on head and pronotum, on anterior margin of the puncture. Lateral margins very widely flattened; flattened areas gradually narrowed posteriorly, widened apically; many minute denticles with short thin setae on anterior half of margins.

Male genitalia ( Figs 4 E–H). Tergite VIII square, a little wider than long, posterior margin rounded, bearing many short setae along posterior margin; sternite VIII with a seta of medium length near each posterior angle, and with some short setae and punctures near lateral margins and posterior angles; spiculum gastrale Y-shaped, thin and somewhat long ( Fig. 4 E). Median lobe ( Fig. 4 G) connected to long and thin median strut by a membrane, median strut 4.5× as long as median lobe, with several punctures around lateral margins of anterior 2/5, half of it covered by setae of short to medium length (ostium was difficult to see in this cleared specimen). Parameres ( Fig. 4 H) fused with phallobase (sutures were difficult to see in this cleared specimen), with a long seta and a few short setae on each apex, with a puncture around each apex. Phallobase ( Fig. 4 H) pentagonal; tegminal strut narrowed anteriorly from middle. Internal sac ( Fig. 4 F) long, containing paired sclerotized plates with rods around base, and thin fiberlike structure around apex.

Type series. Holotype: male, Ulu Gombak , Setapak Subdistrict, Gombak District, Selangor State, Malaysia, 6‒16. V. 2016, FIT with light, T. Yoshida leg. ( ELKU).

Distribution. Malaysia.

Etymology. The specific name refers to the shape of the lateral pronotal teeth.

Remarks. The shape of the lateral pronotal teeth resembles those of Acorimus and Afrocorimus , but D. zigzag can be distinguished by the combination of absence of ventral antennal grooves and 2-segmented antennal club.

Figures

FIGURE 1. Habitus of Dentirotacorimus gen. nov. spp. in dorsal (A, C) and ventral (B, D) aspect. A, B, Dentirotacorimus reticulatus sp. nov., holotype; C, D, Dentirotacorimus zigzag sp. nov., holotype. Scales: 1.0 mm; a for A and B, b for C and D.

FIGURE 4. Dentirotacorimus zigzag sp. nov., male. A, Right antenna; B, right hind leg, ventral view; C, metatarsus, ventral view; D, abdominal ventrites; E, eighth and ninth abdominal segments, ventral view; F, internal sac, ventral view; G, median lobe, ventral view; H, tegmen, ventral view. Scale: 0.2 mm for A – C, E – H and 0.4 mm for D.