Lasioglossum malachurum

Lasioglossum malachurum, the sharp-collared furrow bee, is a small European halictid bee. This species is obligately eusocial, with queens and workers, though the differences between the castes are not nearly as extreme as in honey bees. Early taxonomists mistakenly assigned the worker females to a different species from the queens. They are small (about 1 cm), shiny, mostly black bees with off-white hair bands at the bases of the abdominal segments. L. malachurum is one of the more extensively studied species in the genus Lasioglossum, also known as sweat bees. Researchers have discovered that the eusocial behavior in colonies of L. malachurum varies significantly dependent upon the region of Europe in which each colony is located. L. malachurum was described by the entomologist William Kirby in 1802. This species of bees fall within the genus Lasioglossum, which is the largest bee genus. Lasioglossum falls within the family Halictidae, which includes small to midsized bees and is commonly referred to as the sweat bee family because the Halictidae are frequently attracted to human perspiration. L. malachurum falls within the order Hymenoptera, a large order of generally winged insects containing wasps, bees, and ants. One species of lasioglossum that is closely related to the L. malachurum is L. hemichalceum. Physical size is a major distinguishing feature between queens and gynes versus female worker bees. Queens consistently are larger in body size than workers. Queens also tend to have worn wings and worn mandibles as a result of higher activity, in addition to greater ovarian development correlating with the reproductive capacity of queens. Queens also generally have abundant fat stores. This physical dimorphism persists throughout all stages of the lifecycle, from pupae to adult. Rarely, queens can be abnormally small compared to the size of workers, but abnormally large workers have never been observed in the wild. The sweat bee has a simple nesting architecture consisting of a vertical tunnel into the ground ending in a compartment reserved for brood-rearing. They nest underground, like Lasioglossum zephyrum, but they do not form the same complex structures. Nest entrances are frequently concealed using scattered foliage. For L. malachurum, thousands of nests can be found located within a small region in nesting aggregations, which suggests that the bees likely have some sort of identification mechanism for conspecific nests. In fact, nest entrances and brood cell linings are both impregnated with secretions from the Dufour's gland of the bees, which plays a role in nest orientation. Nests are dug into hard, compact soil and can be sealed from within by the queen using her abdomen. Because nests are dug into hard soil, construction of a nest represents a significant energy expense to a queen, which explains why gynes frequently usurp other nests rather than founding one of their own. 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. L. malachurum is found across England, continental Europe, and northern Africa, so is capable of inhabiting a broad range of habitats and climates. Differences in the climes of the various habitats can frequently impact the social behavior of L. malachurum within that habitat. The length of summer, for example, can affect the length of the breeding season and thereby impact the number of broods a queen may have. 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. Female workers in southern European colonies of L. malachurum consequently have significantly more developed ovaries than their counterparts in northern European colonies. 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. Researchers have identified a tendency for L. malachurum in southern European climes to be characterized by more activity and the production of more worker broods prior to the production of a gyne brood, whereas L. malachurum in northern European climes exhibit less activity and only a single worker brood prior to the gyne brood. 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. Although several females usually outwinter in the same burrow with little conflict, they start to act aggressively until a single female is left in possession of the burrow, leaving the evicted females to obtain or excavate burrows of their own. Each female with a nest tunnel then begins to build brood cells in short side passages which she excavates to the side of the main passage. Immediately following construction, each brood cell is mass-provisioned with a mixture of pollen and nectar in the form of a firm, doughy mass. An egg is laid on each pollen mass and the individual cell sealed by the female. Each egg takes 22 days to develop from an egg to a full adult. She then goes on to construct more, similar cells containing eggs and pollen masses. During this time, before the first worker brood has emerged, containing only about five workers, the foundress queen frequently leaves the nest to find provisions to build the brood cells of the nest. These nest absences are accompanied by high risk of intraspecific usurpation. Once the brood is provisioned, the queen seals the nest synchronously with all other queens in the aggregation, and all above-ground activity ceases for three weeks.