Halictidae, Thomson, 1869

Walker, Kenneth L, 2022, Taxonomic revision of the Australian native bee subgenus Australictus (Hymenoptera: Halictidae: Halictini: genus Lasioglossum) - “ Wood-Splitting Axe Bees ”, Memoirs of Museum Victoria 81, pp. 135-162 : 135-136

Halictidae is the second largest bee family in the world, with

4,510 species ( Ascher and Pickering, 2022), and is found on all continents except Antarctica ( Michener, 2007). Most of this species richness is concentrated in the tribe Halictini , with 2,882

species ( Ascher and Pickering, 2022).

Lasioglossum Curtis 1833 is one of the most species-rich and taxonomically challenging groups of all world bee genera, with 2,645 named species to date ( Ascher and Pickering, 2022). Lasioglossum bees are distinguished from other Halictini genera by having the third submarginal (2rs-m) (‘‘strong-veined Lasioglossum series’’) and sometimes the second submarginal cross veins (1rs-m) (‘‘weak-veined Hemihalictus series’’) weaker than the first submarginal cross vein ( Michener 2007, see especially figs. 66–6a and c).

The Australian component of this most diverse genus within the Halictidae has 308 available names ( ABRS, 2022a; note: update to ABRS, 2022a includes changes for Callalictus Michener 1965 – see Walker (2022); and here, Homalictus Cockerell 1919 is treated as a subgenus of Lasioglossum – see Danforth, 1999, Danforth et al., 2001, 2003, 2008; Gibbs et al., 2012, 2013; Zhang et al., 2022). In Australia, Lasioglossum is divided into nine subgenera as follows: Australictus Michener 1965 (11 species); Austrevylaeus Michener 1965 (six species); Callalictus (three species); Chilalictus Michener 1965 (139 species); Ctenonomia Cameron 1903 (nine species); Glossalictus Michener 1965 (one species); Homalictus (46 species); Parasphecodes Smith 1853 (92 species); and Pseudochilalictus Michener 1965 (one species).

The subgenus Australictus , with 11 available names, is a striking Lasioglossum subgenus of the Australian bee fauna. The subgenus occurs from north Queensland (two species), down coastal New South Wales, across Victoria, widely in Tasmania (two species), and there are three specimen records from south-east South Australia (figs. 12A–E). Bees of this subgenus nest in wood, either excavating their own nests or modifying the vacated burrows of beetles. This is the first record of wood-nesting Halictidae in Australia. To accommodate this wood-nesting behaviour, the mandibles of females have been modified as described below.

A full morphological diagnosis for the subgenus Australictus is provided. Species can be generally distinguished from other Australian Lasioglossum subgenera by the following characters: body length moderately large (females: 8.32 mm to 10.23 mm; males: 8.01 mm to 10.21 mm); female head widened basally in frontal view, with lower inner eye width almost equal to or wider than upper inner eye width (fig. 1A); bidentate mandible of females with elongated and enlarged preapical tooth (fig. 1C) and broadened at base (fig. 1E); female labrum medium process truncate apically with lateral margins pectinate (fig. 2A); dorsolateral angles of pronotum rounded (figs. 5A, 6A, 7A, 8A, 9A); body colour black, one species with metasoma red-brown (figs. 6A, 6B); several species with no body tomentum (figs. 5A–D, 6A–D, 8A–D), several species with various combinations of yellow/white tomentum on dorsolateral angles of pronotum, mesoscutum, metanotum and basal band across metasomal T2-T3 (figs. 7A–D, 9A–D); female anterior metatibial spur finely serrate (fig. 2B); and male genitalia with gonobase either basally widened (figs. 10A, 10B, 11C, 11D) or narrowed (figs. 10C–F, 12A, 12B), retrorse lobe either short (figs. 11A, 11C) or elongate (figs. 10A, 10C, 10E) and gonostylus either short (figs. 10A, 10C, 11A) or absent (figs. 10E, 11C).

The shape of the female mandible, especially in dorsal view, is broad basally and apically pointed (fig. 1E), resembling a wood-splitting axe – hence the common name suggested here, “Wood-Splitting Axe Bees”.

The Australian Lasioglossum subgenus Australictus is revised. Of the 11 available names listed by Michener (1965) for the subgenus, six are placed in synonymy. A species placed by Michener (1965) in the Lasioglossum subgenus Parasphecodes is recombined to the subgenus Australictus and four other species, placed in Parasphecodes by Michener (1965), are synonymised with this valid, recombined taxon, and the species name of the taxon is reverted to its original spelling. In addition, a species placed in Australictus by Michener (1965) is synonymised with a valid species in the Lasioglossum subgenus Chilalictus Michener 1965 . These changes provide five valid names for the subgenus Australictus .

All valid species are redescribed, keys to both sexes, montage images and distribution maps are provided to assist with species identifications.