Genus: Lasioglossum

Lasioglossum bees are small, common, and largely unknown to many people.

The Lasioglossum bee genera is the largest in the world! It contains over 1700 different Lasioglossum species 1. Lasioglossum are so prevalent, they can be found on all continents excluding Antarctica 2. Despite this, Lasioglossum bees are largely unknown, probably because they are very unremarkable 3. The common name for Lasioglossum bees is sweat bees because they are attracted to human sweat for its salt content. The common name 'sweat bee', unfortunately, encompasses many different types of bees. So, I will be using 'Lasioglossum' or 'Lasioglossum bees' to reference this specific group of bee species.

Lasioglossum mainly feed on pollen and nectar from plants. This makes them both palynivores (an animal that eats pollen) and nectarivores (an animal that eats nectar). Pollen provides Lasioglossum with protein and fat, and nectar provides them with carbohydrates in the form of sugar and starches. Lasioglossum don't collect nectar in large quantities and instead mix nectar with pollen to create bee bread. Bee bread, which is apparently doughy in consistency, is provisioned with their developing larvae.

Lasioglossum bees are important pollinators despite not being as hairy or as large as other pollinators. Lasioglossum are common and populous pollinators. They are so populous on flowers that they may contribute comparatively to honey bees and bumble bees on some crop plants 3. Some Lasioglossum species are also capable of buzz pollination which is the only method of pollination for certain crops and flowers. Buzz pollination is when a bee grabs a flower with its pincer like mouthparts and vibrates her thorax to dislodge pollen from the flowers 4. Pollen will not dislodge from some flowers unless they are buzz pollinated. Some crops that require buzz pollination include tomatoes, potatoes, kiwis, eggplants, cranberries, and blueberries 5.

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These photos show a sweat bee in a hairy cat's ear flower. This is the typical sight when you find these bees in open flowers. They almost appear to be swimming in the petals and anthers! This bee is likely in Halictidae, but it is difficult to identify from just these pictures.

Here, you can see several features that identify this insect as a bee. The long and slender elbowed antennae are on the head of the bee. The bee is also covered in pollen, indicating that it has been visiting flowers. Finally, the bee appears to be swimming in this flower. This indicates that this bee is foraging, which is a behaviour that is usually only seen in bees.

This photo is very zoomed in which makes it difficult to get an idea of its size. For context, this bee is probably around 5 mm in length. In order to spot tiny sweat bees foraging in flowers, you need a very sharp eye. Once you spot one or two though, you'll see them everywhere! They are the easiest to see in large open flowers like buttercups and dandelions.

Lasioglossum bees are mostly solitary, but...

Lasioglossum bees have been shown to exhibit a range of social behaviours, with different levels of organisation and cooperation. So, some Lasioglossum are solitary (with one female doing all of the work), some are eusocial (with a queen, workers, and drones), and some are parasitic. Some species actually exhibit more than one type of sociality!

Most Lasioglossum are solitary bees. The bees that do not associate with others within their species are called solitary bees. "Female solitary bees are all capable of producing offspring, they all build and maintain their own nest, and they all forage for the floral resources... necessary for provisioning their brood cells" 6. Solitary bees do not have a colony, so no queen, drones, or workers.

Some Lasioglossum live communally. Lasioglossum "typically live alone, but some form communal nests in which multiple reproductively active females share a common main burrow" 6. Communal bees live in the same area and several females share a nest, but each female is responsible for her own eggs and offspring 7. In these communal bees, each female behaves effectively as a solitary bee, and there is no obvious cooperation among nest mates 6.

Some Lasioglossum are social. Lasioglossum bees differ from more advanced social bees, like honey bees or bumble bees, in that queens are similar in appearance, queens are larger than workers, new nests are established by only one queen bee, and the nests usually last one active season" 6. They also have a single queen who does most of the egg laying, but workers are capable of laying their own eggs too!

Finally, some Lasioglossum are parasitic bees 8. There are two types of parasitic bees. Brood parasites are parasitic bees that lay their eggs in the prepared and provisioned nests of solitary bees 6. Social parasites are parasitic bees that attack the "nest of a social host and effectively replaces the resident queen as the egg-laying female, while, at the same time, co-opting the resident workforce to rear her own offspring".

The photo shows the slender furrow bee (Lasioglossum calceatum). As can be seen, this bee has a brown colouration, sparse hairs on its thorax, and hairy hind legs.

The slender furrow bee can be found in Europe and throughout Japan. It is a bee of interest because it appears to be both solitary and primitively eusocial. One study found that in areas with a shorter active season, L. calceatum acts like a solitary bee with each female making its own nest and provisioning brood 9. However, L. calceatum exhibits primitively eusocial behaviour in areas with a longer active season.

It is thought that this is only able to become social in areas where more than one generation of workers can be produced. We're only scratching the surface of understanding with these bees!

"Lasioglossum calceatum. Slender Furrow Bee" by gailhampshire is licensed under CC BY 2.0.

The life cycle of a solitary Lasioglossum bee and their nesting behaviours.

The life cycle of a solitary Lasioglossum includes four stages: egg, larva, pupa, and adult.

Egg: The female solitary bee will lay eggs individually or in small groups, often in a pre-constructed nest or in a natural cavity such as a hollow stem or a burrow in the ground.
Larva: Once the egg hatches, the emerging larva will feed on a provision of pollen and nectar that the female bee has left with the egg. The larva will go through several moults as it grows, eventually reaching its full size.
Pupa: After the final moult, the larva will spin a cocoon and enter the pupal stage. In this stage, the bee's body undergoes metamorphosis, developing into an adult bee.
Adult: Once the pupal stage is complete, the adult bee will emerge from the cocoon. The adult bee will then forage for food, reproduce and repeat the cycle. Adult solitary bees typically live for several weeks to a few months, depending on the species.

It's worth noting that some species of Lasioglossum will have a slightly different life cycle, for example, some Lasioglossum species have a two-year life cycle. In a two year cycle, the adult bees overwinter (which is basically like hibernating) and the next generation of bees emerges the following spring.

Lasioglossum make a variety of nests, but most nest in the ground. Some Lasioglossum excavate their nests, while some use nests from previous years 10. There is little study on nesting preferences and variety for Lasioglossum, but we can assume they will nest where other ground nesting bees have been found: ground nesting bees can prefer sand dunes, sandy soil, silty soil, or soil with lots of clay depending on the species 3. Nests are constructed using a variety of techniques: bees can pick up dirt with their mandibles, dig using their hind legs, and pack dirt into the walls to make their nest more stable 6. Nests are built in a wide variety of ways, but most are a single tunnel dug vertically down with branching horizontal tunnels for the developing brood.

"Lasioglossum turret 1" by RobertoLeonardi2 is licensed under CC BY-SA 4.0.

This is a photo of a Lasioglossum nest! This bee has constructed a tube of cemented dirt (also known as a turret) at the top of its nest. You can also see the abdomen of the bee poking out of the top of this turret.

The turret is part of the nest and is thought to have various uses. The turret may prevent dirt and soil from falling into the nest entrance, prevent flooding, prevent nest parasites from finding the nest entrance, allow for heat regulation within the nest, and act as areas of scent deposition so individual females can recognize their own nest 6.

Some interesting Lasioglossum species of note.

Lasioglossum oenotherae is a species of Lasioglossum bees found in temperate eastern North America. This bee only feeds on evening primrose. Due to this, these bees have specialised hairs that collect pollen from evening primroses only 11. This makes these bees specialists as they only feed on one type of flower. Finally, the females of this species forage on plants at dusk, dawn, or at night. This is a fairly unique feature in bees as most forage during the warmest periods of the day (this is known as diurnal behaviour).

Lasioglossum coeruleum is a deep blue metallic bee that is found on the east coast of North America. This bee is one of a few Lasioglossum bees that has been recorded nesting primarily in rotting logs instead of in the ground 12. Their nests are usually started in abandoned insect burrows in the wood and they expand their nests from these cavities.

Finally, new species of Lasioglossum are consistently found! This is because many of them are small and inconspicuous. In 2022, there were two species of Lasioglossum that were named, both named after the researchers who had first recorded them. The first species named in 2022 was Lasioglossum delphiae, a bee named after Dr. Casey Delphia who is a member of the Montana State University research community who currently focuses on bee documentation in Montana 13. She collected L. delphiae in a 2009 trip to St. Lucia, a Caribbean island. She collected these bees in dry forest or beach habitats on the island coast. The second species named in 2022 was Lasioglossum onuferkoi, a bee named after Dr. Thomas Onuferko who is an expert on sand dune habitat 14. Lasioglossum onuferkoi was discovered in sand dunes that straddled the Alberta-Saskatchewan border. This is a rare habitat in the prairies in Canada and it is slowly decreasing due to invasive plant introduction 15.

This collage allows you to see some of the variety within Lasioglossum species! Lasioglossum have been called, "morphologically monotonous", so the Lasioglossum near you may not be as varied or brightly coloured as the species shown here. However, this collage really showcases how different these bees can look! These are all photos taken by Sam Droge for the U.S. Geological Survey. Pictures are not to scale.

A) Lasioglossum tarponense, B) Lasioglossum egregium, C) Lasioglossum foxii, D) Lasioglossum truncatum, E) Lasioglossum heterorhinum, F) Lasioglossum sisymbrii, G) Lasioglossum versatum, H) Lasioglossum vierecki, I) Lasioglossum havanense.

How can you help Lasioglossum bees in your yard or garden?

By providing food, nesting sites, and a pesticide-free environment, you can help support Lasioglossum bees, and other bees and pollinators, in your yard or garden. It's important to remember that the success of your efforts will depend on the specific species of Lasioglossum present in your area, as well as the environment and availability of resources.

To provide food in your yard, make sure you have a variety of native flowering plants in your yard, as well as plants that have different blooming times. Lasioglossum bees can be specialist or generalist foragers. So, by providing a wide variety of flowers for nectar and pollen, you are providing them with good food sources. You will also need to plant native wildflowers that bloom at different times throughout the growing season to provide a steady source of food for the bees. Some Lasioglossum only forage for a few weeks out of the year, so having some flowers blooming will help all of the possible visiting pollinators.

When you are tending your garden, make sure you don't use pesticides. Pesticides can be harmful to bees and other beneficial insects, so it's important to avoid using them in your yard or garden 16. Instead, try using natural pest control methods such as companion planting and handpicking pests.

In addition to using little to no pesticides, I encourage you to become a messy gardener! Solitary bees, such as Lasioglossum, need a place to lay their eggs and rear their young. You can provide nesting sites for many of these bees by leaving bare patches of soil 17. Messy gardeners also mow less! Many species of Lasioglossum are ground-nesting, and mowing too frequently can destroy their nests. If possible, leave a small area of your yard unmowed or, if not mowing is not possible, mow it less frequently with the blades on the highest setting on your mower.

Page information

Author: Melissa Platsko

Date published: February 12, 2023

References

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