Lasioglossum zephyrus

The order Hymenoptera contains more eusocial species than any other order. Eusociality has many origins and is present in many degrees within Hymenoptera, with L. zephyrus being one of the more primitive examples. Six species within this genus have reverted to solitary life, social polymorphism, or parasitism. ==Description and identification==

Lasioglossum zephyrus is characterized by its dark green metallic color, reddish abdomen, and a hairier face than most other species. Males are 6 to 7 millimeters long, slightly larger than females. Males are distinguished from females by their brighter green color and redder abdomens. Since the castes vary along a spectrum, there is no definite way to distinguish a worker from a queen based on appearance alone. ==Distribution and habitat==

L. zephyrus has been found throughout the United States, in the months of March through October. Nests are usually constructed in April along the south facing edges of streams, and are clustered in aggregations of up to 1,000 nests. It nests in burrows that are typically constructed by young females. However, older females may also contribute to burrowing if their nests have been destroyed. These females excavate primarily at night, but activity has been reported throughout the day. Workers use their mandibles to loosen the soil, then carry it a short distance to be picked up by another bee. This soil is ultimately smoothed over the walls or used to fill evacuated old burrows. Females excavate cells and line them with a liquid produced in their enlarged Dufour's glands and secreted from the apex of the abdomen. ==Colony cycle==

Lasioglossum zephyrus nests consist of less than 20 individuals. During the spring, around April, new nests are established by one or more females. Some of these nest may never gain more members, and the female will remain solitary. If they do expand, the colony will reach its maximum size of 10–20 around August. Growth of the colony is gradual throughout the summer. Inseminated young queens overwinter in their nests so that the cycle may be repeated. However, overwintered queens are likely to die early on in the summer. After the death of an old queen, a new queen takes over within hours. L. zephyrus colonies have a high mortality rate, especially when inhabited by a solitary bee lacking guards. ==Behavior==

Dominance hierarchy Roles within the colony are indirectly determined by age or physical differences, but direct determination is made by dominance interactions. Queens have been shown to back workers into the depths of the burrows, preventing them from foraging and growing larger queen sized ovaries. When the queen dies, another worker takes her place and begins reproduction. Queens and workers are not very physically distinct, since bee size varies on a continuum. Early in the spring, the males are solitary or clustered in small groups, but by late summer they gather in swarms of thousands of bees. Within these swarms there are head-on collisions between bees as they search for females and flowers. ==Communication and recognition==

Individual bees can recognize their nest and nest mates by their odors, which helps to prevent parasitism by unrelated L. zephyrus as well as other species. This recognition has been documented in both males and females. Males can identify individual females by their unique odors and learn to avoid females who are unreceptive to mating. L. zephyrus has also been shown to leave foreign nests even without being attacked, which supports the theory that they use odors to identify their home nests. ==Kin selection==

Genetic relatedness In Hymenoptera species, like Lasioglossum zephyrus, females are diploid and males are typically haploid, in a system called haplodiploidy. However, in inbred L. zephyrus populations, and also in other hymenopteran species, diploid males have been discovered. Hymenopteran workers are expected to be related by a coefficient of 3/4, assuming the queen only mates only once. While learning does play a role in kin recognition, the genetic differences in odor are thought to be more critical in kin recognition. Kin recognition is beneficial for defense of the entire nest, as well as at the individual level. Individuals benefit by contributing only to the fitness of their own related nest mates. ==Diet==

Adult Lasioglossum zephyrus feed their larva pollen from surrounding plants. Since they forage at a variety of different flowers, they collect multiple types of pollen. Some types are more protein dense than others, but the adults do not compensate for the difference in pollen quality. All offspring receive the same amount of pollen, which results in offspring of different sizes. Size is an advantage for females because it gives them a better chance of becoming a queen. They also tend to produce more eggs of better quality, and greater size increases the chance that a female survives the winter. Larger males are better able to defend territories and compete for mates. Size is also a factor for both species in regards to flight. Larger body size leads to an increased body temperature and the ability to fly sooner in the season and with greater frequency. This species has been observed forcing open unbloomed flowers of species Xyris tennesseensis to extract the pollen, ensuring first and exclusive access. ==Interactions==

Parasites Lasioglossum zephyrus has been parasitized by diverse organisms including bacteria, fungi, protozoa, and other species of hymenoptera. Nematodes have been found in the abdominal cavities of L. zephyrus females, and have led to a reduction in ovarian development. Parasites that attack in the spring during nest founding tend to be most successful. If threatened, the bee may try to attack it or decapitate the intruder. Guard bees are often responsible for the protection of the nest and will send one member to attack while the others block the entrance with their abdomens. Nests containing only infected females are in danger of dying out. While infected bees are able to excavate burrows, they are less active than healthy bees and do not collect pollen to make cells. Gregarine protozoa have been found generally in older specimens of L. zephyrus. It is thought that once a bee is infected, it takes time for the spores to fully develop. These parasites have only been found in females, although it is unclear why males remain unaffected. The bee species Lasioglossum cephalotes is a kleptoparasite of L. zephyrus. The mutillid Pseudomethoca frigida is also a parasitoid, and known to engage in aggressive fights with female L. zephyrus. Instead of stinging its opponent, L. zephyrus attempts to decapitate it. The mutillid retreats, unable to defend itself. ==References==