Hydrochus purpureus Knisch

Perkins, Philip D., 2019, Type designations for Neotropical water beetles in the genus Hydrochus Leach 1817 (Coleoptera: Hydrochidae), Zootaxa 4701 (2), pp. 149-167 : 159-160

Hydrochus purpureus Knisch

Figs. 8 , 13C

Hydrochous purpureus Knisch 1920: 57 .

The RBINS kindly provided seven syntypes of Hydrochus purpureus Knisch , which are part of the Orchymont/ Knisch types collection. The syntypes consist of three males, three females, and one specimen of unknown gender (a prior worker dissected the specimen, but there are no apical genital segments or male genitalia with the specimen). One of the syntype females bears a lectotype label, by J. L. Hellman, but this designation was never published. This label has been reversed and “unpub.” written on the reverse side. There are at least three species represented by the syntypes. The males represent two species which markedly differ externally, and the male genitalia also distinctively differ. I have selected one of the two males from Brazil, “Matto Grosso,” to serve as lectotype, have labeled it such, and have imaged the habitus, male genitalia and labels of this specimen ( Figs. 8 , 13C ). The other male from “Matto Grosso” is conspecific with the lectotype. The third male, clearly a different species, is from Argentina, and bears a label “ Hydrous corruscans Bruch A. d’Orchym. Rev. ” Lectotype labels ( Fig. 13C ): “Bras.Corumba [Matto Grosso] // Coll. A. Knisch COTYPUS // det. Kniž purpureus // coll. A.d’Orchymont // HABITUS/GENIT. DIGITAL IM- AGES captured 2019 P.D. Perkins // [red] LECTOTYPE Hydrochus purpureus Knisch desig. P. D. Perkins. ” The six non-lectotype syntypes have been labeled paralectotypes.

Remarks. The lectotype, plus the second male from Mato Grosso, one of the females from Mato Grosso, and the syntype of unknown gender distinctively differ from the other syntypes in having a deep cervical sulcus, a groove behind the eyes into which fits the arcuate anterior margin of the pronotum (for descriptions of other species with this character see Perkins, in press). This rather obvious character has not been mentioned by previous authors, including Makhan (1992). Oliva (1992), in the “Material examined” section listed six syntypes, but did not designate a lectotype. The description in Oliva (1992) cannot be conclusively evaluated because it is unknown which syntype was used for the description, or if the description is a composite based on two or more specimens.

Figures

FIGURE 8. Hydrochus purpureus Knisch, habitus and male genitalia of lectotype.

FIGURES 13A–E. Labels of lectotypes and neotype. (A) Hydrochus metallipes Knisch; (B) Hydrochus pumilio Knisch; (C) Hydrochus purpureus Knisch; (D) Hydrochus tarsalis Chevrolat; (E) Hydrochus secretus Knisch.