Hexacylloepus keitai, 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 : 23-24

Hexacylloepus keitai sp. nov.

( Fig. 8 A–B)

Type locality: Mexico, San Luis Potosi State, La Cova.

Diagnosis: Antennae without setae. Frontoclypeal suture inconspicuous. Pronotum with a short and deep impression on disc. Hypomera with a belt of tomentum reaching the lateral and anterior margins. Epipleura with tomentum. Tibiae each with a row of setae on distal half; meso- and metatibiae each with a row of spines in distal half. Abdomen with the disc of the first ventrite without tomentum, and a deep depression with a pair of carinae extending towards and reaching the metaventrite.

Description: Male. Body elongated, subparallel. Black colour, with the antenna, mouthparts and legs reddishbrown. Total length: 1.61 mm. Greatest width: 0.70 mm.

Head: surface with micropunctures separated from each other by their diameter and with short setae. Antenna inserted on the anterior margin of the eyes, filiform, with 11 antennomeres without setae. Frontoclypeal suture inconspicuous. Clypeus 5x as wide as long; anterior margin strongly concave and posterior sinuous; surface similar to that of head. Labrum twice as wide as long; antero-lateral angles rounded and surface with micropunctures. Maxillary palpus 4-segmented; terminal palpomere truncated apically. Labial palpus 3-segmented. Mentum and submentum rectangular.

Thorax: Pronotum as long as wide, arcuate anteriorly; sides sinuate and serrate, posterior margin smooth with two prescutellar foveae ( Fig. 8A ). Surface with micropunctures and setae. Sublateral carinae complete, sinuous and raised ( Fig. 8A ). Longitudinal impression deep on disc.

Elytra moderately longer than wide; anterior margin arcuate, lateral margin moderately arcuate and serrate; rounded apex ( Fig. 8A ). Humeri slightly prominent. Surface with puncture and setae rows. Elytral suture moderately elevated. Carina short and elevated on interval IV, extending from base to 1/5 of the elytral length; sublateral carinae on intervals VI and VIII, extending from base to 3/4 of the elytral length. Epipleura with tomentum ( Fig. 8B ). Hind wings macropterous. Scutellum oval.

Prosternum narrow, strongly elevated; surface with micropunctures, anterior margin straight with many setae and lateral margin covered with tomentum. Disc moderately raised. Prosternal process long and narrow and beyond the procoxae; lateral margin elevated; rounded apex. Notosternal suture slightly sinuous. Hypomera wider posteriorly than anteriorly, lateral margin serrate; surface with micropunctures and with a thin belt of tomentum reaching the lateral and anterior margins ( Fig. 8B ).

Mesoventrite with a groove to receive the prosternal process. Mesepimeron and mesepisternum covered with tomentum. Metaventrite broad with a longitudinal medial depression; surface with micropunctures, sides covered with tomentum.

Legs (except tarsi) covered with punctures and tomentum ( Fig. 8B ). Coxae rounded; trochanters elongated; femora short and robust, 3x as long as wide, 1/4 of the elytra length; tibiae short and thin, 4x as long as wide, with 1/4 of the elytra length; tibiae each 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 longer than the basal four combined. Claws long and thin.

Abdomen ( Fig. 8B ): five ventrites, as long as wide; strongly raised on middle. 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 with a deep depression and a pair of carinae extending towards and reaching the metaventrite. Fifth ventrite with lateral margins slightly produced posterolaterad; and apex rounded with long setae.

Female: External morphology similar to male, except for the absence of the row of spines on the meso- and metatibiae.

Material examined: 3 specimens.

Distribution: Mexico: San Luis Potosi State.

Male holotype: ♂ | La Cova . SLP / x.70 Mex. / 23km C. Valles / H.E.Hinton | H.E.Hinton / collection. / B.M.1977-566 . | Hexacylloepus n. sp. / det. Spangler | Holo- / type ( NHMUK).

Paratypes: 2 specimens ♀ | La Cova. SLP / x.70 Mex. / 23km C. Valles / H.E.Hinton | H.E.Hinton / collection. / B.M.1977-566. | Hexacylloepus n. sp. / det. Spangler | Para- / type (NHMUK).

Etymology: keitai is a tribute to Keita Matsumoto, Curatorial Assistant of the Coleoptera collection at NHMUK.

Comparative notes: Hexacylloepus keitai sp. nov. resembles H. granulosus ( Sharp, 1882) by the inconspicuous frontoclypeal suture, pronotum with the longitudinal impression short and deep on disc, and short legs. However, the species can be differentiated by the epipleura in H. keitai sp. nov. completely covered with tomentum and hypomera with belt of tomentum reaching the anterior and posterior margin, while in H. granulosus the epipleura lack tomentum and the belt of tomentum on the hypomera only reaches the lateral margin.

Comments: The new species was found in the NHMUK collection and had already been recognised as a new species by P. Spangler (no further information) but never published. Spangler studied and dissected the three specimens (one male and two females), but unfortunately, we were not able to find the aedeagus of the male. However, the species has several external morphological characters that clearly identify it as a new species and allowed it to be described.

Figures

FIGURE 8. Hexacylloepus keitai sp. nov.. Male. Holotype. Habitus. (A) Dorsal view. (B) Ventral view. Scale bars = 0.5mm.