The Genus <I>Desmopachria</I> Babington, Subgenus <I>Portmannia</I> Young (Coleoptera: Dytiscidae)


  • Frank N. Young


The subgenus Portmannia Young (1980) of the Neotropical genus Desmopachria is characterized by its ovate, sometimes almost globose body form, smooth shining integument between relatively fine punctures, and sexually dimorphic prostemal process. In the females the prosternal process comes to a point as in other members of Desmopachria, but in males the process is bifid or forked. The species are found from Texas and Arizona to Brasil in South America. They are particularly abundant in Mexico. A key is given for twelve species which are described and figured. The following species are described as new: decorosus (Mexico), goias (Brasil),pittieri (Costa Rica), sobrina (Mexico) and zethus (Mexico). The color is variable. Some species are relatively darkly colored without distinct darker markings, and usually with some coarser punctation on part of the dorsum. These seem to be characteristic of the tropical forests (D. laevis Sharp and D. specula Sharp. D. goias is also dark with vague spots on the elytra). Most of the Mexican and Central American species are characterized by at least parts of the elytra being lighter in color than the head and pronotum, sometimes strikingly contrasting. The latter group may or may not have a distinct dark color patterns of the elytra or on head and pronotum. In both groups some species are intensely dark brown or black beneath, but this character may be influenced by degree of hardening of the cuticle. Nearly all the species have darker markings along the suture of the elytra and base of the pronotum. Some species are distinctly patterned on the elytra which probably represents disruptive coloration helping to conceal them in the clear, sand-bottomed habitats in which most occur.