Lasioglossum problematicum (Blüthgen 1923)

Sakagami et al. (1994) describe nest guarding behavior in a Japanese population of this eusocial species: Queens guarded the nest entrance while foragers were away foraging. Sakagami et al. (1984) discuss overwintering ecology of this species and its influence on social behavior. Females overwinter communally in their burrows, meaning that when they begin nesting in the spring the nest is polygynous. This is in contrast to other conspecific sweat bees, like Lasioglossum duplex, which overwinters singly, and thus starts spring nesting with a solitary phase before the worker brood emerges. Ebmer et al. (1994) briefly refer to results of studies of "hundreds of nests" between 1957 and 1984 by Sakagami, apparently unpublished: the authors state that "ethologically this species is really 'problematical'". It exhibits social variation: females may nest solitarily, or "semisocially", in which females who emerge in a single autumn overwinter together and nest together in the spring, as described by Sakagami et al. (1984). Colonies may be solitary one year, but eusocial the next if daughters overwinter with their mother and both nest together the next spring (this implies that there is division of labor in which one bee forages and the other reproduces, although the authors do not explictily say this). If in one (or both) generations the mother or daughter is joined by other females, the resulting colony the subsquent spring will be an association of "stepsister or step-mother-daughter associatons", that is, individuals unrelated to the original mother and/or daughter. The typical temperate eusocial life cycle, in which a reproductive female emerges in the autumn, overwinters, and then initiates a nest solitarily in the spring which becomes eusocial when the first brood of daughters remain at the nest as workers "was confirmed only once as an ephemeral case".

Lasioglossum problematicum là một loài Hymenoptera trong họ Halictidae. Loài này được Blüthgen mô tả khoa học năm 1923.