Abstract
I propose a redefinition of the sexstrigatus group of Lasioglossum (Hemihalictus) Cockerell, 1897, including a phylogenetic analysis. This group is characterised by a combination of the following 12 characteristics: male antenna short, not attaining to metasoma, male labrum with distal process and well-developed basal elevation, male head with genal process as variation, female mesepisternum reticulate-punctate on lower area, mesepisternum without tubercle in both sexes, female metasomal terga with distinct fimbriae on posterior margin, male S8 with well-developed median process, gonobase ventral arm of male genitalia connected with each other at upper ends, gonocoxite of male genitalia smooth, gonostylus of male genitalia small and simple, bud-like, and the ventral retrorse lobe of male genitalia not attaining to gonobase. The Japanese species of the sexstrigatus group are revised. Thirteen species in total are recognised, including three new species: Lasioglossum (Hemihalictus) ikudomei sp. nov., L. (H.) spectrum sp. nov., and L. (H.) subsimplicior sp. nov. Lasioglossum (Hemihalictus) perplexans (Cockerell, 1925) is synonymised under L. (H.) kiautschouense (Strand, 1910). A key to the Japanese species is provided. Bionomical data, such as flight and flower records or habitat, are reported for some species. The distributions of all species are mapped. DNA sequences including a part of the barcode region are given for L. (H.) kiautschouense, L. (H.) ohei Hirashima & Sakagami, 1966, L. (H.) speculinum (Cockerell, 1925), L. (H. ) spectrum sp. nov., L. (H. ) subsimplicior sp. nov., and L. (H. ) taeniolellum (Vachal, 1903).
Highlights
Hemihalictus Cockerell, 1897 is a subgenus of Lasioglossum Curtis, 1833 (Halictidae Thomson, 1869, Halictinae Thomson, 1869), with approximately 250 species worldwide (Ascher & Pickering 2020)
The sexstrigatus clade is defined by six homoplasious synapomorphies: 1) the male head with genal process (3:0); 2) the distal process of male labrum present (13:0); 3) the female metasomal terga with fimbriae on apical margin (21:0) (secondarily lost in L. (H.) sphecodicolor); 4) the male S8 with developed median process (23:0); 5) gonobase ventral arms of male genitalia connected with each other at upper ends (24:0); and 6) the ventral retrorse lobe of male genitalia not reaching gonobase (28:1)
The morphological differences among species of the sexstrigatus group often depend on subtle characteristics such as the sculpture of the mesoscutum or T1 and the length of metapostnotal ridges, etc., as described in the diagnosis of each species and the above Key
Summary
Hemihalictus Cockerell, 1897 is a subgenus of Lasioglossum Curtis, 1833 (Halictidae Thomson, 1869, Halictinae Thomson, 1869), with approximately 250 species worldwide (Ascher & Pickering 2020). (Hemihalictus) by various researchers (e.g., Blüthgen 1934; Ebmer 1975, 1986; Warncke 1975; Ebmer & Sakagami 1985; Sakagami & Ebmer 1996). At present, these species groups have been reclassified by Pesenko (2007a) into the following 12 groups: 1) clypearis group, 2) crassepunctatum group, 3) laevinode group, 4) limbellum group, 5) longirostre group, 6) nitidiusculum group, 7) marginellum group, 8) pallidum group, 9) pauperatum group, 10) semilucens group, 11) sexstrigatus group, and 12) villosulum group. The species of L. (Hemihalictus) are morphologically similar to each other, even in the Pesenko’s system, there remains ambiguity in the definition of each group
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