Desmopachria striola, Sharp, 1887

Miller, Kelly B. & Wolfe, G. William, 2019, Three New Species in the Desmopachria striola Species-Group of Desmopachria Babington, 1841 (Coleoptera: Adephaga: Dytiscidae: Hydroporinae: Hyphydrini), The Coleopterists Bulletin 73 (3), pp. 621-628 : 622-623

The Desmopachria striola species-group

Diagnosis. The Desmopachria striola speciesgroup is defined as those Desmopachria species with a distinct sutural stria on the elytron ( Young 1980, 1990; Miller 2001). The group is heterogeneous, and the male genitalia are dissimilar across the entire group as currently defined. Several species, however, including Desmopachria grouvellei Régimbart , Desmopachria ruginosa Young , Desmopachria striola Sharp , and those species described herein seem to have similar genitalia with the median lobe in ventral aspect “shouldered” medially (laterally expanded) to varying degrees and the lateral lobe apically with a more-or-less abruptly obliquely bent flat lobe (e.g., Figs. 3, 4 ). Even so, this group requires additional investigation to determine if it is natural and what is its diagnostic combination.

Comments. Guignot (1950) described the subgenus Pachriostrix (type species D. grouvellei ) to include Desmopachria species with a distinct sutural stria. Young (1980) retained the definition of the group but noted that the group may well be artificial given the diversity of forms of the male genitalia and other features. He later noted the same thing when revising the genus ( Young 1990), at which time he also described a new species and removed some from the subgenus. Miller (2001) discarded the Desmopachria subgenera, including Pachriostrix , and instead recognized this group of species as the D. striola species-group. The group remains problematic. Several species, including the new species described herein and D. striola , have seemingly similar male genitalia with features as described under the diagnosis above, whereas others (specifically Desmopachria amyae Miller , Desmopachria chei Miller , and Desmopachria fossulata Zimmermann ) have rather different male genitalia but remain included because of the sutural stria on the elytron ( Fig. 1 ). Desmopachria amyae has genitalia similar to those of species in the D. portmanni species-group, especially Desmopachria duodentata Braga and Ferreira Jr. Desmopachria chei has male genitalia more similar to that of Desmopachria rex Gustafson and Miller and Desmopachria varians Wehncke than to other species in the D. striola species-group. It certainly seems possible that the sutural stria is an unreliable character as an indicator of monophyly, though such a dispositive evaluation will require a larger phylogenetic analysis of the group.

Young (1980) included D. fossulata in Pachriostrix and later included an image of the genitalia of the species based apparently on a drawing from J. Balfour-Browne ( Young 1990); inexplicably he did not key it or address the species further in that revision. The genitalia ( Fig. 18 ) are rather different from those of other D. striola species-group members, and it is not clear that it comports well with the definition of the group.

Figures

Figs. 1–24. Desmopachria species. 1) D. atropos, habitus; arrow indicates sutural stria; scale bar = 1.0 mm. Male genitalia: D. atropos: 2–3) Median lobe, right lateral and ventral aspects, respectively; 4–5) Right lateral lobe, right lateral and ventral aspects, respectively. D. clotho: 6) Median lobe, right lateral aspect; 7) Median and right lateral lobes, ventral aspect; 8) Right lateral lobe, right lateral aspect. D. lachesis: 9–10) Median lobe, right lateral and ventral aspects, respectively; 11–12) Right lateral lobe, right lateral and ventral aspects, respectively. D. amyae, redrawn from Miller (2001): 13) Median and left lateral lobes, dorsal aspect; 14) Median lobe, right lateral aspect; 15) Right lateral lobe, right lateral aspect. D. chei, redrawn from Miller (1999): 16) Median and lateral lobes, dorsal aspect; 17) Right lateral lobe, right lateral aspect. D. fossulata, redrawn from Young (1990): 18) Median and lateral lobes, ventral aspect. D. grouvellei, redrawn from Young (1990): 19) Median and lateral lobes, ventral aspect. D. ruginosa, redrawn from Young (1990): 20–21) Median and lateral lobes, ventral and right lateral aspects, respectively. D. striola: 22) Median lobe, right lateral aspect; 23) Median and right lateral lobes, ventral aspect; 24) Right lateral lobe, right lateral aspect.