About Green Bees

Green sweat bee Quick Facts

Common name	Green sweat bee
Scientific name	Augochlora pura
Kingdom	Animalia
Phylum	Arthropoda
Class	Insecta
Order	Hymenoptera
Family	Halictidae
Genus	Augochlora
Type	Solitary sweat bee
Diet	Nectar and pollen; licks sweat for salt
Habitat	Eastern evergreen woods
Native range	Eastern United States
Colours	Metallic green, blue or gold
Special feature	Attracted to human sweat

Life Cycle of Green Bees

Augochlora pura, often called the pure gold-green sweat bee, is a small bee found in eastern North America, from southern Canada through the eastern United States. It is about 8 to 10 mm long and has a shiny, metallic green body. These bees are useful pollinators in eastern woodlands and visit many kinds of flowers. They are active from spring through early autumn. Like other sweat bees, they are sometimes attracted to human sweat, which they lick for its salt.

Like all bees, Augochlora pura goes through complete metamorphosis, which has four stages: egg, larva, pupa and adult. Scientists have not measured exactly how long each stage lasts, but growing from egg to adult takes a few weeks. Development is faster when the weather is warm.

The Biology

Adult females usually collect food from morning until mid-afternoon. They start by gathering nectar and then make several trips to collect pollen. A female may need up to about ten pollen trips to stock a single nest cell. She mixes the pollen and nectar together to form a small food ball for her young.

Unlike most sweat bees, which dig nests in the soil, Augochlora pura nests in rotting logs and stumps. Each female chews a tunnel into the soft, damp wood and builds small cells along it. She defends her nest from other females and from parasites, but otherwise lives alone. Females often build new cells late in the day and may reuse old tunnels that other bees have left behind.

At night, females usually rest inside their nest tunnels or shelter in rotting wood. Although they live alone, several females may nest close together in the same log if it is a good spot. Females can sting, but the sting is mild, and they usually only sting if they are pressed or trapped, for example when someone squashes one while it is licking sweat from their skin.

Males do not help build or look after nests. Instead, they spend their days flying around flowers, looking for females to mate with. In the afternoon and at night, males rest in holes in wood, sometimes sharing a hole with several other males. Male bees do not have stingers, so they cannot sting at all.

Eggs

A female lays one egg in each nest cell, on top of a ball of pollen mixed with nectar. The cell walls are lined to keep the inside moist, so the egg does not dry out. The egg is white, long and slightly curved. In warm weather, it hatches after just a few days.

Larvae

When the larva hatches, it feeds on the pollen ball inside its sealed cell. Young larvae can dry out easily if their cell is damaged, but older larvae are tougher. Once the larva has eaten all of its food, it rests for a while as a prepupa and then turns into a pupa. Like many bee larvae, it waits until it has finished eating before getting rid of its waste.

Larvae grow faster in warm conditions than in cool ones. They are soft, white and grub-like, with no legs and only a small head. Over a short time they grow from tiny hatchlings into plump grubs many times their starting size.

Pupae

Although the pupa does not move, big changes are happening inside it as it turns into an adult bee. During this stage it forms its wings, legs, antennae and other adult body parts. Pupae are better at resisting drying out than eggs or young larvae.

The adult bee forms inside its cell. It stays there until its outer skeleton hardens, and then it chews its way out into the world. Female pupae are larger than male pupae, just as adult females are bigger than adult males. A pupa already looks a lot like an adult bee, with its legs and wings folded against its body.

Adults

Adult bees feed on nectar and some pollen while they visit flowers. Augochlora pura is a solitary bee, which means there is no queen and there are no workers: every female builds her own nest and lays her own eggs. Females guard their nests and will chase away other insects that try to move in.

Both males and females are active through the warm months. Males are more common early in the season, while females become more common later on.

Scientists are not sure exactly how long adults live. Mated females from the last generation of the year survive the winter, usually tucked inside rotting logs or old nest tunnels, and start new nests in spring. Males die in the autumn and do not survive the cold. In the southern part of the range there can be two generations a year, while in the north, where summers are shorter, there is usually only one.

Adult Augochlora pura bees are beautiful insects. Their hard outer shell (exoskeleton) is covered in tiny pits and ridges, and it shines in bright metallic colors that can look green, blue-green or golden depending on the light. This sparkling color makes them easy to spot on flowers.

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