Diestostemma bituberculatum, Signoret, 1855

Pinto, Ângelo Parise, Mejdalani, Gabriel & Takiya, Daniela Maeda, 2017, Unraveling the white-clothed Diestostemma Amyot & Serville: a taxonomic revision of the American sharpshooters of the D. bituberculatum complex (Hemiptera: Cicadellidae), Zootaxa 4281 (1), pp. 135-164 : 160-162

Diestostemma bituberculatum complex and Leucopepla Kirkaldy, 1907

Leucopepla was erected to include the single species Tettigonia bituberculata Signoret, 1855 (type species by monotypy) by Kirkaldy (1907, p. 87) in a key to genera of the “tribe Tetigoniini”, which generic composition coincides fair well with the current concept of Cicadellinae . He distinguished Leucopepla from Zyzzogeton Breddin, 1902 by the “Pronotum with 2 crescentiform tubercles”, while the latter has flattened processes. At that time, only the five Signoret (1855) species and the Fabricius (1803) D. albipennis were included in Diestostemma (see Walker 1858) and, as a result, the newly erected Leucopepla was distinguishable based on presence of two large humps on the pronotum.

In his revision of Diestostemma, Schmidt (1910) overlooked Kirkaldy’s (1907) paper and, without examining a specimen, placed D. bituberculatum in “Gruppe II” based on the female terminalia along with eight other species (seven currently valid), all with the posterodorsal surface of the pronotum not significantly elevated. Conversely, Melichar (1924, p. 211) recognized Leucopepla as valid, although noting that it was very similar to Diestostemma (“Von der Gattung Diestostemma Am. et Serv. nur dadurch verschieden, dass sich auf dem Pronotum zwei Höcker befinden.” [From the genus Diestostemma Am. et Serv. only differs by the two humps on the pronotum.]). Based on the dorsally elevated pronotum, Melichar (1924, p. 211) added two new species in Leucopepla , the still enigmatic L. atropunctulata Melichar, 1924 and L. reticulata Melichar, 1924 , both considered by him with “Pronotumhöcker niedrig, mehr abgeflacht” [Pronotum hump low, more flattened]. A few years later, Schmidt (1928) described a fourth species in the genus with large pronotal humps, Leucopepla rubriventris Schmidt, 1928 , based on a single female that could be distinguished from the similar L. bituberculata by the shape of female sternite VII and differences in coloration.

The genus composition remained unaltered including these four species in Metcalf’s (1965) catalog in which Leucopepla was included in his new tribe Ciccianini with the genera Acrobelus Stål, 1869 , Cicciana Metcalf, 1952 , and Yunga Melichar, 1924 , until Young’s (1968) revision, when the genus was synonymized with Diestostemma . The latter author stated that the pronotal character “integrates” with other species in the genus. Indeed, the pronotal hump-shaped tubercles (varying from slightly to strongly projected) are also observed in a few other species of Diestostemma , such as D. reticulatum ( Figs. 11–12 ), D. atropunctulatum (though less projected), and among brownish species with densely sclerotized forewings ( D. nervosum group), including an undescribed species from Peru known to the present authors. However, all these above-cited humped species are clearly distinct from Leucopepla sensu stricto ( D. bituberculatum complex) based on the general coloration, antennal ledge shape, relative size of the pronotal posterolateral angle, shape and number of SVDs, and male and female terminalia. Although we agree with the distinction of Leucopepla s.s., we do not propose further changes in the classification until a robust phylogenetic hypothesis of the whole genus is available. We prefer to treat the strongly homogenous group of large white Diestostemma species from the Amazonian forest as the D. bituberculatum complex, excluding D. atropunctulatum and D. reticulatum .

The arrangement of metafemoral macrosetae varies considerably in the D. bituberculatum complex, both intra- and interspecifically. Often there are additional macrosetae located close to the AD row, with equal size or slightly smaller in a few cases. We are not confident in considering these as regular macrosetae of the PD row. These supernumerary macrosetae vary from just one at second to fourth positions (additional macrosetae to AD2–4), as in the holotype of D. cavichiolii sp. nov., to an extreme of four macrosetae in the third row of the female paratype of D. olivia sp. nov. The frequencies of different macrosetal arrangements on the metathoracic leg are given in Table 1. Further comparative study is needed to determine whether this unusual configuration is observed in other genera of Cicadellinae .

Based on samples from the canopy fogging project in the Ecuadorian Amazon by T. Erwin (USNM), Dietrich & Wallner (2002) observed a very high number of undescribed leafhopper species, thus it is not surprising that three out of the four new species described herein were collected during the same project. Other new sharpshooter species have already been described based on this material (e.g., Ceotto et al. 2004; Takiya & Cavichioli 2005; Cavichioli & Takiya 2012), but there are many more to describe. Considering the high number of undescribed leafhoppers in these samples, Dietrich & Wallner (2002) estimated that the number of leafhopper species in the world could reach 200,000. It is impossible to determine at this point if the species herein described are exclusively canopy dwellers, as the collecting method is not selective and understory species could also be collected.

Considering Diestostemma , a full revision of this genus based on the examination of type specimens is urgently required, taking into account that, as in many other Proconiini genera (see Dietrich 2013), several species are known only from meager material and are poorly characterized. The generic status of Diestostemma appears well supported by diagnostic morphological characters, as well as the genus group nomina Leucopepla and Heterostemma , but phylogenetic analyses should be undertaken to determine whether taxa currently treated as junior synonyms of this genus should be reinstated. The inclusion of D. cavichiolii sp. nov. in the D. bituberculatum complex is somewhat questionable, because this species has somewhat atypical characteristics, such as the less projected humps on the pronotum. Likewise, D. reticulatum , originally described in Leucopepla , probably belongs to this group, although the shape of the female sternite VII is distinct from those of other species in the complex.

Additional material examined. Diestostemma reticulatum ( Melichar, 1924) . PERU. 1 ♂, 1 ♀, [Departamento de Cusco, Provincia de Quispicanchis, Distrito de Camanti], 3 rd km E Quincemil PE 2012-004 [(coord. 13°13’03”S, 70°43’40”W, 633 m a.s.l.), 31.VIII.2012, D.M. Takiya leg.] ( DZRJ) .

Figures

FIGURES 1 – 12. Head and prothorax of species of the Diestostemma bituberculatum complex in anterior view. 1 – 2. Male holotype and female paratype of D. albinoi sp. nov. (Ecuador, Orellana Province, EPNC, USNM); 3 – 4. Male and female of D. bituberculatum (Signoret, 1855) (French Guiana, Cayenne Arrondissement, INHS, DZRJ); 5 – 6. Male holotype and female paratype of D. cavichiolii sp. nov. (Brazil, Mato Grosso State, DZUP); 7 – 8. Male holotype and female paratype of D. gervasioi sp. nov. (Ecuador, Orellana Province, EPNC, USNM); 9 – 10. Male holotype and female paratype of D. olivia sp. nov. (Ecuador, Orellana Province, EPNC, USNM); 11 – 12. Male and female of D. reticulatum (Melichar, 1924) (Peru, Cusco Department, DZRJ). Scale bars = 2 mm.