Crucisternum sinuatus, Girón & Short, 2018

Giron, Jennifer C. & Short, Andrew Edward Z., 2018, Three new genera of acidocerine water scavenger beetles from tropical South America (Coleoptera, Hydrophilidae, Acidocerinae), ZooKeys 768, pp. 113-158 : 120

Crucisternum sinuatus sp. n. Figs 3A-D ; 6G, H ; 7

Type material examined.

Holotype (male): BRAZIL: Minas Gerais: Lassance, -17.83384, -44.50515, 568 m, Cachoeira da Palmeira, flotation of root mats and moss from side of waterfall and seepage, 2.iii.2018, leg. Benetti & team; BR18-0302-04A (INPA). Paratypes (10): BRAZIL: Pará: Rio Xingu Camp 52°22'W, 3°39'S, Altamira, ca 60km S., 3.x.1986, leg. P. Spangler & O. Flint, Colln. #6, 1st jungle stream on trail 1 (1, USNM); same, except 14.x.1986, Colln. #23, stream on left branch of trail 1 (3; SEMC, USNM); Minas Gerais: same data as holotype (2 INPA, 4 SEMC).

Differential diagnosis.

Crucisternum sinuatus is very similar to C. escalera and C. xingu in the shallowness of the punctation. In addition, it can be distinguished from C. xingu by the aedeagus with median lobe constricted at midlength, continuing as a narrow and roundly pointed bar (see Fig. 6G, H ; as opposed to gradually narrowing towards the apex, see Fig. 6E, F ), and the outer margins of the parameres, which are strongly constricted at apical third, continuing nearly parallel (as opposed to nearly straight to sinuate).

Description.

Body length 2.0-2.4 mm, width 1.1-1.4 mm. General coloration variable, either orange brown or uniformly dark brown (Fig. 3A-D ). Elytra with punctures shallowly marked. Aedeagus with outer margins of parameres strongly constricted at apical third, continuing nearly parallel towards apex; inner margins of parameres slightly concave only along apical sixth; median lobe constricted at midlength, continuing as a narrow and roundly pointed bar (Fig. 6G, H ).

Etymology.

Named in reference to the abrupt constriction of the outer margins of the parameres at their apical third, with the Latin word sinuatus meaning bent, curved.

Distribution.

Brazil (Minas Gerais, Pará). See Fig. 7 .

Biology.

The series from Lassance was collected by floating root mats and detritus that were on rock at the margin of a river and waterfall. The specimens from Altamira were collected in streams.

Figures

Figure 3. Habitus of Crucisternum spp.: A-D Crucisternum sinuatus: A dorsal view B lateral view C ventral view D head E-H Crucisternum xingu: E dorsal view F lateral view G ventral view H head. Scale bars: 1 mm.

Figure 6. Aedeagus of Crucisternum spp.: A-B Crucisternum ouboteri: A Guyana B Brownsberg C Crucisternum toboganensis D Crucisternum vanessae E-F Crucisternum xingu: E colln 6 F colln 23 G-H Cuscisternum sinuatus: G colln 23 H BR 18 - 0302 - 04 A I Crucisternum escalera J Crucisternum queneyi. Scale bars: 0.25 mm.

Figure 7. Distribution of Crucisternum species.