[1] This species is obligately eusocial, with queens and workers, though the differences between the castes are not nearly as extreme as in honey bees.

They are small (about 1 cm), shiny, mostly black bees with off-white hair bands at the bases of the abdominal segments.

[5] Physical size is a major distinguishing feature between queens and gynes versus female worker bees.

[1] The sweat bee has a simple nesting architecture consisting of a vertical tunnel into the ground ending in a compartment reserved for brood-rearing.

[9] L. malachurum is a Western Palaearctic species and nests can be found across Southern England and the Channel Islands, most of continental Europe, and North Africa.

[10][11] L. malachurum is found across England, continental Europe, and northern Africa, so is capable of inhabiting a broad range of habitats and climates.

The longer breeding seasons in Southern Europe can also lead to reproductive capacity in worker bees, making L. malachurum in those regions not purely eusocial.

[1] Due to the relatively broad range of nesting habitats of the species, L. malachurum is subject to a myriad of climate-based selective pressures that cause a differential in behavior dependent upon location.

[1][12] The queens of L. malachurum, following fertilization the previous year, begin to appear in the spring, when food sources are plentiful to sustain them after the long overwintering period.

Immediately following construction, each brood cell is mass-provisioned with a mixture of pollen and nectar in the form of a firm, doughy mass.

[9] Larvae from the earliest eggs are full grown and start pupation by the end of May in Central Europe (or much earlier in warmer climates), emerging from their cells by mid-June.

For bees in cooler climates with shorter breeding seasons, these adults are all non-reproductive female workers, somewhat smaller than their mother.

The original maternal female bee remains within the nest and guards the entrance to the burrow, now acting as a queen while her non-reproductive daughters act as workers; they go out foraging for food and help in the construction of new brood cells, in which the queen lays new eggs.

The chemical distinctions between the pheromones released by virginal and mated queens are significant in terms of proportions of hydrocarbons and lactones.

They are also capable of discriminating between familiar and unknown queens, and l generally are more attracted to queens of a foreign colony, which likely arose as an outbreeding mating strategy, which increases genetic diversity of the population and decreases the probability that the next generation would be subject to genetic disease.

This form of scent blending is found commonly among other members of Hymenoptera including certain bees, wasps, and ants.

[2] Early nest closure has been favored by pressure from usurpation and has developed into an evolutionarily stable strategy.

[9] The nest aggregation of thousands of colonies that persists throughout the year becomes a lek mating system on warm summer days in the latter half of the breeding season (July through September).

The daily operational sex ratio has far more males than females, which is common in a lek mating system and among other bees.

[16] Males are attracted during mating by a mix of olfactory cues produced in multiple glandular sources from the female.

[2] Aggression is commonly seen between conspecifics of all halictid bees; especially between usurper females, drawn out fights can occur that last for nearly a half-hour and result in damage to or loss of limbs and body parts.

[17] L. malachurum bees are polylectic, meaning that they collect pollen from a broad range of unrelated plant species.