New species and records of Chasmogenus Sharp, 1882 from the southwestern margin of the Guiana Shield (Coleoptera: Hydrophilidae: Acidocerinae) Author Glynn, Rachel D. Author Short, Andrew Edward Z. text Zootaxa 2021 2021-10-07 5048 3 435 443 journal article 4051 10.11646/zootaxa.5048.3.8 e80cf6ad-d7b3-48a3-9527-5c3e2c4cd83c 1175-5326 5556559 B1B24583-1DFC-49BA-BDF7-A48F3D74E7E2 Chasmogenus inpa sp. n. Figures 3C , 5A–B , 6 Type Material. Holotype (male): “BRAZIL: Amazonas : Manaus / -2.93079 , -59.97514 , 75 m / Ducke Reserve , trail to Igarape / Acara ; Short & team; muddy/ area with emergent vegetation/ 7–8.vi.2018 ; BR18-0607-01A”, “[barcode]/ SEMC1623365 / KUNHM-ENT” ( INPA ) . Paratypes (7): BRAZIL : Amazonas : Same data as holotype ( 4 exs. , INPA , SEMC ); same locality but Flight Intercept Trap (FIT) ( 2 exs. , SEMC , DNA vouchers SLE1892 and SLE1894); Novo Airão Municipio , -2.68396 , -60.93840 , Densely vegetated margin of blackwater creek, BR17- 0609-04A ( 1 ex. , SEMC , DNA voucher SLE1267) FIGURE 6: Distribution of new Chasmogenus spp. Differential diagnosis. This species is similar to a group that have an aedeagal form with relatively broad, straight parameres and a wide median lobe which is slightly shorter to slightly longer than the apex of the parameres. It is distinctly smaller in overall size than C. amplius Smith & Short, 2020 , C. berbicensis Smith & Short, 2020 , and C. clavijoi Smith & Short, 2020 . The apex of the parameres curve slightly inward like that of C. schmits Smith & Short, 2020 , but are not bluntly squared and the apex of the median lobe distinctly reaches the apex of the parameres or just slightly beyond. It is most similar to the comparably-sized C. guianensis Smith & Short, 2020 , but the median lobe is distinctly longer and even with the apex of the parameres. Description. Size and color. Total body length 3.7–3.9 mm . Body form elongate oval with slightly curved lateral margins. Dorsum of head orange brown to dark brown, clypeus and labrum distinctly paler ( Fig. 3C ). Pronotum and elytra uniformly orange-brown. Venter uniformly orange-brown to dark orange brown. Head. Ground punctation on head fine. Clypeus with anteromedial emargination, which exposes a broadly rounded gap between the clypeus and labrum ( Fig. 3C ). Mentum weakly depressed in anterior third with a triangular to rounded anteromedial notch. Maxillary palps long, longer than width of head immediately posterior to eyes. Thorax. Ground punctation on pronotum fine. Prosternum weakly tectiform. Mesoventrite with moderate elevation forming a thin posteromedial longitudinal carina. Metafemora densely pubescent in basal nine-tenths. Aedeagus. Aedeagus ( Fig. 5A, B ) with median lobe widest at base, and slightly tapering gradually until the apical quarter, then narrowing abruptly to form an acute triangular apex which is even with or extends slightly past the apex of the parameres. Sclerite of the median lobe not expanded. Gonopore situated less than half of one gonopore width below the apex of the median lobe. Parameres symmetrical, with outer margins slightly curved inwardly and apex slightly inwardly curved and bluntly rounded. Basal piece of medium to long length, ca. one half to two-thirds the length of the parameres. Etymology. Named after the Instituto Nacional de Pesquisas da Amazônia, an organization dedicated to advancing our understanding of the Amazon, and who also administers the Adolfo Ducke Forest Reserve from where this species was collected. Distribution. This species is known only from the Ducke Reserve in Amazonas State, northern Brazil . Biology. Collected in muddy vegetated areas along a trail to Igarapé Acará.