[2] The subfamily Halictinae also belongs to the hymenopteran monophyletic clade Aculeata, whose members are characterized by the possession of a modified ovipositor in the form of a venomous sting for predator and prey defense.

[2] The roughly 250 species belonging to the tribe Augochlorini exist only in the New World, mainly inhabiting the Neotropics and some areas of North America.

Though evidence of sociality and nesting biology is limited, observed populations in southern Africa are believed to be solitary.

These cleptoparasitic bees are host generalists and belong to an ancient lineage of parasites that uniquely shares no specificity with any nonparasitic halictine taxa.

Assigned more than 2000 described species, the Halictini are the largest tribe of halictid bees, including considerable behavioral diversity.

Most species belong to the genus Lasioglossum, which encompasses a variety of nocturnal and diurnal, socially parasitic, solitary, eusocial, and communal bees.

Mexalictus includes six described species of rare bees observed in humid areas of high elevation ranging from southeast Arizona to northern Guatemala.

The variety of colony organizations expressed by halictine species is represented along a gradient ranging from solitary nesting to obligate eusociality.

[1][2][3][5] Eusocial behavior is associated with cooperative nesting and brood care, an overlap in adult generations, and a division of social roles, marked by intracolony reproductive hierarchies.

When parasite and predator threats are high and territory and resources are limited, a greater number of individual workers may improve parental care of offspring.

Possession of venomous stinger in the Halictinae were likely beneficial in the subfamily's evolution of eusociality by providing a thwart to the increased predator attention caused by group living.

[2] [9] Phylogenetic data from this species suggests that communal behavior may actually serve as a transitional step between eusociality and an evolutionary reversion back to solitary nesting.

[2] Phylogenies constructed from fossil evidence dating demonstrate numerous reversions within the Halictidae to solitary nesting.

[4] Morphological data were employed in the 1960s to create a phylogeny suggesting the behavioral reversion from eusociality to solitary nesting in the genera Augochlora and Augochlorella.

Workers are capable of laying gyne or male eggs and occasionally do so, limited by the queen's physical control.

[2] A queen can direct the evolution and maintenance of nonreproductive castes of offspring through parental manipulation with the use of pheromones or assertion of behavioral dominance.

[8] Latitudinal, altitudinal, and local variation have been partially ascribed to environmental influences such as flowering season length, temperature, nesting substrate availability, and risk of predation or parasitism.

[1][5] For eusociality to be expressed, the summer breeding season must provide time for consecutive production of both worker and reproductive broods.

A study of L. malachurum in southern Greece demonstrated the local populations’ degree of eusociality varied among colonies and years, a possible result of queen survival differences during breeding seasons.

In comparison to those in northern Greece, southern Greek populations exhibited larger colony sizes, increased ovarian development, decreased worker mating, and a smaller number of worker-sized queens.

[8] Contributing to the vast halictine social diversity, adult female halictines possess the capacity to express any reproductive role their species exhibits and can adjust their social behavior in response to behavioral interactions within their nest and environmental conditions.

[2][5] The degree of this social plasticity differs among halictine species and populations, further contributing to the subfamily's great inter- and intraspecific variation.

[8] Megalopta genalis, a facultative eusocial halictine, has been observed to primarily exhibit solitary nesting while possessing the capacity for cohabitation and social dominance.

[2][7] An individual halictine bee's repertoire of accessible social behaviors is determined by its specific genetic make-up.