Revision of the rare Mesoamerican bee genus Mexalictus (Hymenoptera: Halictidae) with the description of 21 new species.

The Mesoamerican bee genus Mexalictus (Hymenoptera: Halictidae: Halictinae) is a group of rare bees which are found at high elevations from southern Arizona (USA) to Panama. The genus is revised using traditional taxonomic approaches. The following twenty one new species are described: M. albofasciatus Dumesh, n. sp., M. anatolii Dumesh, n. sp., M. astriatus Dumesh, n. sp., M. ayalai Dumesh, n. sp., M. benyamini Dumesh, n. sp., M. diversus Dumesh, n. sp., M. jovelus Dumesh, n. sp., M. genalis Dumesh, n. sp., M. gibbsi Dumesh n. sp., M. guatemalensis Dumesh, n. sp., M. hansoni Dumesh, n. sp., M. hondurensis Dumesh, n. sp., M. laurencei Dumesh, n. sp., M. mandibularis Dumesh, n. sp., M. nicaraguensis Dumesh, n. sp., M. punctatus Dumesh, n. sp., M. raavo Dumesh, n. sp., M. sheffieldi Dumesh, n. sp., M. vera-cruzense Dumesh, n. sp., M. verdazulus Dumesh, n. sp., M. vitriolus Dumesh, n. sp. These and five previously known species are diagnosed, described, illustrated, and keyed. Phylogenetic analysis, based on 43 unordered morphological characters, resulted in 4 equally most parsimonious trees (L=176; Ci=36.4; Ri=56.6). Based upon these results, the sub-generic classification of Mexalictus into Georgealictus and Mexalictus s.str., is resurrected.

Three new species of Neofidelia (Hymenoptera: Apoidea: Megachilidae) from Northern Chile.

Neofidelia apacheta Dumesh and Packer, sp. nov., N. camanchaca Dumesh and Packer, sp. nov., and N. submersa Dumesh and Packer, sp. nov. are described from northern Chile. Neofidelia apacheta is known from large numbers of specimens and localities at moderately high elevation (1600-3200m). Neofidelia camanchaca is only known from the ho-lotype male. Neofidelia submersa is known from the holotype male and a pair of paratypes in poor condition, all from a coastal fog oasis. Comparisons are made with the two previously described species of the genus. The collection of N. apa-cheta from so far north in Chile suggests that Neofidelia is likely to be found in southern Peru. A key for the five species of the genus is provided.

Revision and reclassification of Lasioglossum (Evylaeus), L. (Hemihalictus) and L. (Sphecodogastra) in eastern North America (Hymenoptera: Apoidea: Halictidae).

The black species of weak-veined Lasioglossum (or Hemihalictus series) in eastern North America are revised to clarify their taxonomy and nomenclature and to facilitate identification. A subgeneric classification based upon available phylogenetic data is applied. Lasioglossum (Sphecodogastra) is applied more broadly than any previous usage to include many species typically classified as L. (Evylaeus). The subgenus L. (Evylaeus) is retained but applied narrowly in agreement with phylogenetic results. Lasioglossum (Hemihalictus) has historically been considered monotypic but is here applied to many species of L. (Dialictus) sensu lato (equivalent to the carinaless L. (Evylaeus) of some authors). Usage of L. (Dialictus) is restricted primarily to species with metallic integument. Additional subgeneric synonymies for extralimital taxa are formalized and discussed. Descriptions are provided for each species with a synonymic list, diagnosis, and notes on taxonomy and biology. The recently revised Onagraceae-specialist species of L. (Sphecodogastra) are given abbreviated treatments. Notes on available DNA barcode data are given, with diagnostic characters supplied for closely related spe-cies. One new species is described: L. (Sphecodogastra) seillean Gibbs and Packer and the males of L. fedorense (Crawford) and L. pectinatum (Robertson) are described for the first time. The following three new synonymies are proposed: Lasioglossum (Hemihalictus) sopinci (Crawford), senior subjective synonym of Evylaeus bradleyi Mitchell; Lasioglosum (Hemihalictus) macoupinense (Robertson), senior subjective synonym of Halictus divergens Lovell; and Lasioglossum (Hemihalictus) inconditum (Cockerell), senior subjective synonym of Halictus tracyi Cockerell. Lasioglossum inconditum is here considered to be distinct from the Palaearctic species L. rufitarse (Zetterstedt). A lectotype is designat-ed for Halictus quebecensis Crawford. We present the first record of L. lustrans (Cockerell) and L. swenki (Crawford) in Canada and the first record of L. lusorium (Cresson) east of the Mississippi River. Updated keys to species are provided for the fauna of eastern North America.

Fifteen new species of Chilicola (Oroediscelis) (Hymenoptera: Colletidae: Xeromelissinae) with illustrated keys to the males and females of the subgenus.

Fifteen new species of Chilicola subgenus Oroediscelis are described and illustrated. The following 11 species are from Argentina recording a remarkable diversity and the first records of the subgenus in the country: Chilicola capillitas Packer and Dumesh, new species, C. abrebotellas, Packer and Dumesh, new species; C. goloboffi Packer and Dumesh, new species; C. fritzi, Packer and Dumesh, new species; C. rozeni Packer and Dumesh, new species; C. roigi Packer and Dumesh, new species; C. carpenteri Packer Dumesh, new species; C. calchaqui Packer and Dumesh, new species; C. jaguense Packer and Dumesh, new species; C. cuyense Dumesh Packer, new species; and C. huarpe Packer and Dumesh, new species. Chilicola pustulata Packer and Dumesh, new species, and Chilicola luna Dumesh, and Packer new species, are described from Peru; C. boharti Packer and Dumesh, new species, and C. ashei Dumesh and Packer, new species, are described from Bolivia, where C. carpenteri also occurs. An unusual feature of the male antennae is described: long setae on F2 and F3 (less commonly F4) that are appressed to, and occasionally longer than, the succeeding flagellomere. Additional records for previously described species are listed and a revised key to males is provided as well as a provisional complete key for all females.

Two new species of Geodiscelis Michener & Rozen (Hymenoptera: Apoidea: Colletidae) with a phylogenetic analysis and subgeneric classification of the genus.

Two new species of the genus Geodiscelis are described: Geodiscelis nazcalinea Packer & Dumesh, sp. nov. from Peru (the first record of the genus from that country) and G. phisquiri Packer & Dumesh, sp. nov. from northern Chile. The new species are most closely related to G. longiceps, but differ primarily in having somewhat less elongate heads and in details of the male terminalia. A key to the five known species of the genus is provided as are the results of a phylogenetic analysis based upon 68 characters, and the genus is formally divided into three subgenera: Geodiscelis s. str. Michener and Rozen, Geodiscelis (Nazcoediscelis) Packer and Dumesh, subgenus nov. and Geodiscelis (Thaumoediscelis) Packer and Dumesh, subgenus nov. The two new species described herein belong to subgenus Geodiscelis (Nazcoediscelis). Figures of the most important characters are provided. Tiquilia sp. (Boraginaceae) is the probable floral host of both new species and it is suggested that all species are ground-nesters. Sexual dimorphism in an unusual character is recorded for G. thaumaskelos Packer.