Hexacylloepus thoracica, Polizei & Barclay & Bispo, 2020

Polizei, Thiago T. S., Barclay, Maxwell V. L. & Bispo, Pitágoras C., 2020, Hexacylloepus Hinton, 1940 rises again; 18 new species of a neglected genus (Coleoptera: Byrrhoidea: Elmidae), Zootaxa 4819 (1), pp. 6-48 : 38-40

Hexacylloepus thoracica sp. nov.

( Fig. 15 A–C)

Type locality: Ecuador, Orellana Province .

Diagnosis: Antennae without setae. Frontoclypeal suture inconspicuous. Pronotum with a long and deep longitudinal impression on disc, reaching the anterior and posterior margins. Hypomera with a narrow belt of tomentum reaching the anterior and lateral margins. Epipleura without tomentum. Metaventrite with a longitudinal medial depression, very strongly raised towards the mesoventrite, forming a tubercle. Tibiae each with a row of setae on distal half; meso- and metatibiae each with a row of spines on distal half. Abdomen with the disc of the first ventrite broad and without tomentum. Male genitalia elongated; phallobase twice as long as wide, length similar to the penis; parameres reaching 2/3 of the penis length, 2x wider than the penis; penis elongated with anterior half sinuous and posterior half straight, apex strongly acute.

Description: Male. Body elongated, subparallel. Brown colour, with the antenna, mouthparts and legs reddishbrown. Total length: 1.81 mm. Greatest width: 0.78 mm.

Head: surface with micropunctures separated from each other by their diameter. Antenna inserted on the anterior margin of the eyes, filiform, with 11 antennomeres each one with long thin setae at apex. Frontoclypeal suture inconspicuous. Clypeus 4x as wide as long; anterior margin concave and posterior sinuous; surface similar to that of head. Labrum twice as wide as long; antero-lateral angles rounded and alutaceous; surface without setae. Maxillary palpus 4-segmented; terminal palpomere truncated apically. Labial palpus 3-segmented. Mentum and submentum rectangular. Gula rectangular. Genae covered with tomentum.

Thorax: Pronotum as long as wide, arcuate anteriorly; sides sinuate and serrate, posterior margin smooth with two prescutellar foveae ( Fig. 15A ). Surface with micropunctures and setae. Sublateral carinae complete, sinuous and raised ( Fig. 15A ). Longitudinal impression long and deep on disc, reaching the anterior and posterior margin ( Fig. 15A ).

Elytra 3x as long as wide; anterior margin arcuate, lateral margin moderately arcuate and serrate; raised apex ( Fig. 15A ). Humeri moderately prominent. Surface with puncture rows separated from each other by their diameter. Elytral suture moderately elevated. Carina composed by two rows of punctures. Carina short and elevated on interval IV, extending from base to 1/4 of the elytral length; sublateral carinae on intervals VI and VIII, extending from base to 3/4 of the elytral length. Epipleura without tomentum ( Fig. 15B ). Hind wings macropterous. Scutellum shield-like.

Prosternum narrow, strongly elevated, surface with micropunctures; anterior margin straight and sides covered with tomentum. Prosternal process long, narrow, and beyond the procoxae; lateral margin, concave and elevated arrow-like apex. Notosternal suture sinuous. Hypomera narrow, wider posteriorly than anteriorly; surface with micropunctures and with a narrow belt of tomentum reaching the anterior and lateral margins ( Fig. 15B ).

Mesoventrite with a deep groove to receive the prosternal process. Mesepimeron and mesepisternum covered with tomentum. Metaventrite broad with a longitudinal medial depression, very strongly raised towards the mesoventrite and forming a tubercle; surface with micropunctures, sides covered with tomentum.

Legs (except tarsi) covered with punctures and tomentum ( Fig. 15B ). Coxae rounded; trochanter elongated; femora elongated and thin, 8x longer than wide, 1/3 of the length of the elytra; tibiae long and thin, 10x as long as wide; with the half of the elytra length, with a row of setae on distal half. Meso- and metatibiae each with a row of spines on distal half. Tarsi elongate, with setae; apical tarsomere with the length of the basal four combined. Claws very long and thin.

Abdomen ( Fig. 15B ): five ventrites; as long as wide. Anterior and posterior margins straight on the first and second ventrites and arcuate on the subsequent ventrites, lateral margins rounded. Surface densely covered with tomentum (excepted for disc of first ventrite), micropunctures and short setae. Disc of the first ventrite broad with a deep depression, and with a pair of carinae extending towards and reaching the metaventrite. Fifth ventrite with lateral margins slightly produced posterolaterad; apex tapered and with short setae.

Male genitalia ( Fig. 15C ): (Total length: 0.59 mm. Greatest width: 0.16 mm), symmetrical and elongated. Phallobase twice as long as wide, length similar to the penis. Parameres articulated with the phallobase, reaching 2/3 of the penis length; 2x wider than the penis and twice as long as wide, apex slightly sharp. Penis elongated, anterior half arcuate and posterior half straight, apex strongly sharp; fibula elongated approximately the same length as the penis.

Female: Unknown.

Material examined: 2 males.

Distribution: Ecuador: Sucumbíos and Orellana Provinces.

Male holotype: ♂ | ECUADOR (Orellana) / Payamino Research Station / 0º 29’36.01”S 77º 17’ 29.15”W / 300m Tropical Rainforest / at. M.V. light / 30.vii.2007 | (NHMUK) .

Paratype: ♂ | ECUADOR, Napo [nowadays Sucumbíos] / Lago Agrio / (18KmE) / 28 Aug. 1975 at / Rio Aguarico | Collected on / gravel bar / at blacklight / Langley, Cohen, Cantor & Yingling | HEXACYLLOEPUS / det. P.J.Spangler (USNM) .

Etymology: thoracica is a reference to a tubercle on the metaventrite.

Comparative notes: Hexacylloepus thoracica sp. nov. resembles H. bassindalei Hinton, 1969 with a similar belt of tomentum on hypomera, long legs, and epipleura without tomentum. Nevertheless, the species can be differentiated by H. thoracica sp. nov. having a long, deep longitudinal impression on the disc of the pronotum, reaching the anterior and posterior margins; antennae with all antennomeres with setae; and metacoxae without a spur. Hexacylloepus bassindalei has a short longitudinal impression on the disc of the pronotum, not reaching the anterior and posterior margins; antennae with only the six apical antennomeres with setae; and a long and robust spur on the metacoxae. The male genitalia are also different: in H. thoracica sp. nov. the parameres extend 2/3 of the penis length, and the penis is elongated, with anterior half arcuate and posterior half straight; in H. bassindalei the parameres reach 3/4 of the penis length, and the penis is pointed towards the apex.

Figures

FIGURE 15. Hexacylloepus thoracica sp. nov.. Male. Holotype. (A–B) Habitus. (A) Dorsal view. (B) Ventral view. (C) Ventral view of male genitalia. Scale bars: (A–B) = 0.5mm. (C) = 0.1mm.