The bee genus Chlerogas in Bolivia ( Hymenoptera , Halictidae )

A new species of Chlerogas Vachal (Halictinae, Augochlorini) is described and fi gured from Bolivia, correcting a past mis-association of sexes for Chlerogas boliviensis Brooks & Engel. Chlerogas aterrimus sp. n. is described from two males and a single female collected in the Department of Santa Cruz (Provinces of Florida and Caballero) and is distinguished from C. boliviensis, known only from females, and its other congeners. A revised key to the species of Chlerogas is provided along with a new locality record for C. boliviensis.


Introduction
Bees of the genus Chlerogas Vachal occur in the mountains of Colombia and Venezuela, south through Ecuador and Peru, into Bolivia, a distribution in South American perfectly analogous with that of the unrelated, but similarly long-headed, genus Chlerogella Michener (Engel 2000, Engel 2010).Eleven species have been recognized previously but all are known from a scant few specimens (Brooks and Engel 1999;Engel et al. 2006;Engel and Gonzalez 2009), making this one of the rarer genera of Augochlorini.Th e genus can be recognized most easily by the combination of its elongate head in males and females (8)(9)(10), the reduced number of fl agellomeres in males and females, and the pectinate inner metatibial spur in males (Engel 2000).
In February of this year I received for examination three specimens (two females and one male) of Chlerogas collected in Santa Cruz Department, Bolivia.While one proved to be a relatively shiny example of a female C. boliviensis and the single male a black to dark brown individual clearly conspecifi c to the male I described in 2009 as the previously unknown male for this same species (Engel 2009a), the third specimen was of a distinctly black to dark brown female.Upon inspection this second female was obviously associated with the male based on observable features and, while close to the female of C. boliviensis, was apparently not conspecifi c.Accordingly, I believe my previous association (Engel 2009a) of a male to C. boliviensis was in error.Th e new series before me demonstrates that the three black Chlerogas from Santa Cruz (my original male and the male and female newly revealed) represent an undescribed species, while the actual male of C. boliviensis remains elusive and undiscovered.It is ironic that having waited nearly nine years to publish on the specimen I earlier associated with C. boliviensis in the hopes of further material becoming available (Engel 2009a), that such specimens which herein help to refi ne my circumscriptions of these rare species should make their appearance so quickly thereafter.Such a thing highlights the dynamic nature of systematics and that, no matter how patient one may or may not be, at any moment material may become available to revise our understanding and recast our interpretations.I herein provide a description of this species and update the existing key to species in the hope of encouraging those working in the Andean region to seek these rare bees with diligence.
Th e morphological terminology and format for the descriptions follows that used previously in my studies of Chlerogas (Brooks and Engel 1999;Engel et al. 2006;Engel and Gonzalez 2009;Engel 2009a), except following terminological revisions of Engel (2009b).Th e fi gures are essentially those of Engel (2009a) with supplements.Table 1 summarizes the information available for the 12 currently recognized species.Abbreviations for collections cited herein are: AMNH, American Museum of Natural History (New York, New York); SEMC, Snow Entomological Collections, Division of Entomology, University of Kansas Natural History Museum (Lawrence, Kansas); NHML, Natural History Museum (London, UK).Diagnosis.Th is species can be most readily recognized for the black to dark brown coloration and the basal area of the propodeum lacking distinct striae reaching to the apical margin.For those species in which males are known the structure of the exposed (vide infra) and hidden sterna (Figs 4-5), as well as the genitalia (Figs 6-7) are diagnostic.

Genus
Description.Male: Total body length 13 mm; forewing length 8.6 mm.Head 1.56 times longer than wide, narrower than mesosoma (length 3.23 mm, width 2.07 mm).Gena nearly as broad as compound eye in profi le.Base of clypeus below lower tangent of compound eyes; lower interorbital distance 0.77 mm; upper interorbital   branches, not including apical portion of rachis.Metasomal sternum IV apically with paramedial patches of dense golden setae; metasomal sternum V gently concave medially, with distinct, pale gold setae fringing apical borders except in medial concavity; metasomal sternum VI deeply concave medially, with dark gold to fuscous setae except medially along inner and proximal border of concavity; hidden sterna and genitalia as in fi gures 4-7.
Clypeus and supraclypeal area colliculate with coarse, shallow punctures separated by a puncture width or less; malar space colliculate; remainder of face with small, well-defi ned, nearly contiguous punctures, such punctures blending with colliculate integument on vertex; gena and postgena strongly imbricate to colliculate.Pronotum strongly imbricate; mesoscutum imbricate with small, well-defi ned punctures separated by less than a puncture width except punctures weak around midline and anteromedially, in such areas punctures separated by a puncture width or slightly more; mesoscutellum imbricate with punctures separated by a puncture width or slightly less, medially between tubercles punctures faint; metanotum faintly imbricate with small punctures separated by a puncture width or less; pleura strongly imbricate to colliculate with coarse, shallow punctures separated by 0.5-2 times a puncture width; lateral and posterior surfaces of propodeum imbricate with scattered small punctures on lateral surfaces, basal area strongly granular to imbricate, without distinct longitudinal striae reaching apical margin, although with exceedingly short, weak strigae at extreme base laterally and sometimes medially.Metasoma weakly imbricate, with scattered minute punctures.
Coloration of head, including scape and pedicel, and mesosoma black to dark brown (Figs 1-3); labrum, mouthparts, antennal fl agellum, tegula, legs, and metasoma dark brown.Generally lacking metallic highlights except some scattered, faint, dark metallic blue to purple or coppery highlights on mesosoma and head; wings infumate.Pubescence generally white except as noted above.
Pubescence of head and mesosoma intermingled with more erect black setae; setae of scape black; setae of legs black; tergal setae largely fuscous or fuscous golden apically.
Etymology.Th e specifi c epithet is based on the Latin term ater, meaning "black", and is a reference to the dark coloration of this species relative to its Bolivian congener, C. boliviensis.
distance 0.93 mm; torular-ocular distance 0.20 mm; torular-median ocellar distance 0.65 mm; distance between lateral ocelli 0.23 mm; distance between lateral ocellus and median ocellus 0.08 mm; ocellocular distance 0.22 mm.Scape not reaching to lateral ocellus; pedicel as long as wide; FI as long as wide, about as long as pedicel, length 0.18 mm; remaining fl agellomeres (F) longer than wide; FII 0.27 mm in length; FIII-IV each 0.40 mm in length; FV-VII each 0.43 mm in length; FVIII-IX each 0.47 mm in length; FX 0.67 mm in length.Intertegular distance 1.73 mm; mesoscutellum

Table 1 .
Revised summary of currently recognized species of Chlerogas Vachal (Halictinae, Augochlorini).Known sexes are indicated along with ranges of elevation at which each species has been captured (estimated for three species).