Abstract
Sweat bees in the subgenus Lasioglossum (Dialictus) are one of the most diverse and abundant bee taxa, and a critically important component of bee biodiversity. Yet, the most basic taxonomic knowledge of these bees is lacking in many regions. As a step towards a better understanding of the L. (Dialictus) of the western Nearctic region, a revision of the ‘red-tailed’ L. (Dialictus) species was completed. Thirty-six species were revised, 20 of which are described as new, and two names are treated as junior subjective synonyms. Descriptions, figures, distribution maps, floral hosts, and keys to species for females and males are provided. The following 20 species are described as new: Lasioglossum (Dialictus) arenisaltans sp. nov., L. (D.) argammon sp. nov., L. (D.) austerum sp. nov., L. (D.) cactorum sp. nov., L. (D.) cembrilacus sp. nov., L. (D.) clastipedion sp. nov., L. (D.) clavicorne sp. nov., L. (D.) decorum sp. nov., L. (D.) festinum sp. nov., L. (D.) imbriumbrae sp. nov., L. (D.) julipile sp. nov., L. (D.) lilianae sp. nov., L. (D.) meteorum sp. nov., L. (D.) miltolepoides sp. nov., L. (D.) minckleyi sp. nov., L. (D.) perditum sp. nov., L. (D.) rufornatum sp. nov., L. (D. ) spivakae sp. nov., L. (D.) tessellatosum sp. nov., and L. (D.) torrens sp. nov. Previously unknown males of L. (D.) clematisellum (Cockerell, 1904), L. (D.) droegei Gibbs, 2009, L. (D.) kunzei (Cockerell, 1898), and L. (D.) pallidellum (Ellis, 1914) are described and figured for the first time. Lasioglossum (Dialictus) clarissimum (Ellis, 1914) (= Halictus clarissimus Ellis, 1914) and L. (D.) perexiguum (Sandhouse, 1924) (= Halictus (Chloralictus) perexiguus Sandhouse, 1924) are new subjective junior synonyms of L. mesillense (Cockerell, 1898) (= Halictus nymphalis var. mesillensis Cockerell, 1898). A lectotype specimen is newly designated for L. mesillense, for which the location of the type material has not previously been known. The following five new records for Mexico are reported: L. clematisellum, L. droegei, L. eophilus (Ellis, 1914), L. kunzei, and L. pallidellum.
Highlights
Sweat bees (Hymenoptera: Halictidae) are one of the most abundant and species-rich components of native bee communities
Halictidae are commonly collected by any method appropriate for bees (Morse 1960; Sakagami et al 1967; Allred 1969; Tommasi et al 2004; Batáry et al 2010; Smith et al 2012), but especially with pan traps or ‘bee bowls’ (Toler et al 2005; Campbell et al 2007; Gonçalves & Oliviera 2013; Buri et al 2014; Geroff et al 2014; Joshi et al 2015; Griffin et al 2017; Onuferko et al 2017; Rhoades et al 2017b; Lettow et al 2018; Portman et al 2020), in which they can exceed 90% of individuals (Droege et al 2010; Gonzalez et al 2020)
L. (Dialictus) are an unavoidable and critical part to Nearctic bee biodiversity, thorough revisions only exist for Canada (Gibbs 2010) and the eastern United States (Gibbs 2011)
Summary
Sweat bees (Hymenoptera: Halictidae) are one of the most abundant and species-rich components of native bee communities. (Dialictus) are an unavoidable and critical part to Nearctic bee biodiversity, thorough revisions only exist for Canada (Gibbs 2010) and the eastern United States (Gibbs 2011). In the western United States and northern Mexico, the focal area of this work (hereafter generally referred to as ‘western’), no comprehensive revision has been completed. (Dialictus) are Gibbs (2010), which includes western Canada and is applicable to some of the northwestern United States, or Sandhouse (1924), which does not cover a well-defined area but includes a large number of western species. (Dialictus) of California, the Rocky Mountains, and perhaps other regions, including many new species descriptions. These were never published, and some of his original manuscripts may have been lost
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