Adelphydraena amazonica, Perkins & Ribera, 2020

Perkins, Philip D. & Ribera, Ignacio, 2020, Three new species and DNA sequence data of the rare South American water beetle genus Adelphydraena Perkins, 1989 (Coleoptera: Hydraenidae), Zootaxa 4858 (1), pp. 35-52 : 36-37

Adelphydraena amazonica , new species

Figs 1 , 2 , 13 (habitus), 14 (map)

Type Material. Holotype (female): “ Brasil, Ducke , Igarapé afluente Acará Laje, água corrente, S 02º 57’07.4” W 059º 57’27.6”, U.G. Neiss col.” (date unknown) ( INPA). Specimen used for DNA extraction and sequencing (specimen voucher IBE-AN591).

Differential diagnosis. Differentiated from other Adelphydraena by the combination of the very broad body form (ca. 1.50 x 0.83 mm; elytra almost as wide as long), the markedly chordate pronotum with large tumidities, the elytra with serrate margins anteriorly, and the comparatively narrow metaventral plaques ( Figs 2 , 13 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.50/0.83; head width 0.44; pronotum 0.43/0.68, PA 0.51, PB 0.48; elytra 0.89/0.83. Habitus as illustrated ( Fig. 2 ). Color: Dorsum dark brown, legs and maxillary palpi testaceous. Head: Frons finely sparsely punctate, punctures smaller than eye facets; shiny in middle, microreticulate and dull laterally; posterior line not extended forward at juncture of shiny and microreticulate areas. Clypeus finely punctate, punctures denser than frons, interstices effacedly microreticulate. Labrum slightly longer than clypeus; median emargination setose, length nearly 0.75x labrum length; apicolateral angles without spinose projection. Eyes small in dorsal aspect, width ca. 1/6 interocular distance. Mentum elongate, narrowed anteriorly, lobe on each side of apicomedian emargination curved ventrally and toward midline; apical width ca. 0.5x basal width. Genae without posterior ridge. Pronotum: Pronotum subcordiform. Posterior half of disc with raised, rounded relief on each side of midline, posteriorly in midline confluent with one another, reliefs separated anteriorly by four large punctures; reliefs very shiny, very finely, sparsely punctate, punctures similar to those of frons. Punctures posterior to reliefs very coarse and dense, forming two transverse rows, punctures of anterior row larger and deeper than posterior row, punctures of anterior row separated from one another by narrow walls, posterior row punctures separated by ca. 1x puncture diameter. Punctures along anterior margin of discal reliefs coarse, but smaller than posterior punctures, punctures in area anterior to coarse marginal punctures becoming progressively smaller until very fine near anterior margin of pronotum, punctures shallow, bottoms apparently flat with central seta, interstices shiny, ca. 1–2x puncture diameter. All interstices anterior to discal reliefs with extremely sparse, very fine micropunctures similar in size to those of discal reliefs. Lateral depressions with punctures near anterior and posterior angles, intervening area nearly impunctate, very shiny. Lateral margin denticulate anterior to middle. Anterior margin weakly trisinuate. Posterior margin very weakly bisinuate, nearly straight. Elytra: Each elytron with 9 complete rows of punctures, tenth row represented by few punctures anteriorly; punctures on disc ca. as large as medium sized punctures on pronotal disc. Intervals raised slightly, shiny, 3–4x puncture diameter; interstices ca. 1x puncture diameter. Raised humeri connected with slightly produced anterior angles. Lateral margin strongly arcuate, anterior 0.5 serrate, explanate margin well developed, at midlength ca. 2x distal width of metatibia. Anterior margin with extremely small, posteriorly produced acute process at base of second interval. Prosternum: Prosternal intercoxal process slightly wider than mesoventral intercoxal process; prosternal midline length 2x prosternal intercoxal process width. Prosternal postcoxal process flat between submedian carinae. Mesoventrite: Mesosternal intercoxal process length 1x width, apex slightly arcuate. Metaventrite: Plaques small ( Fig. 13 ). Abdomen: Distance separating coxal cavities ca. 1.2x mesosternal intercoxal process width. Legs: All legs without apparent modifications. Flight wings: Fully developed.

Etymology. The name is an adjective referring to the geographical distribution.

Remarks. Unfortunately, the terminal abdominal segments and the spermatheca were lost during the DNA extraction process.

Figures

FIGURE 1. Dorsal habitus of Adelphydraena species.

FIGURE 2. Adelphydraena amazonica n. sp., habitus of holotype.

FIGURE 13. Ventral habitus of Adelphydraena species.