Life Cycle

Almost all the native bees in Alberta lead a solitary life, each female constructing and provisioning her own nest without any help from other members of her species. Solitary bees usually live for about a year. The active adult stage when bees forage for pollen and nectar usually lasts about three to six weeks. During the remainder of their life cycle, bees will be hidden in a nest, growing through the egg, larval and pupal stages.

Nesting

The majority of native bee species in Alberta nest in the ground, digging tunnels in bare or sparsely vegetated, well-drained soil. Some species prefer sandy soils and others prefer loamy soils. Ground-nesting bees use a plate (called pygidial plate) on their end of their abdomens to tamp down the soil in their nest. Bumble bees frequently nest in places such as mouse burrows. Many solitary bee species nest in abandoned beetle burrows or other tunnels in snags (dead or dying standing trees). They may chew out a nest within the soft central pith of stems and twigs. A few species nest in potlike cells that they construct from pebbles and tree resin. Female cavity-nesting bees will lay eggs in cells in a single line that fills the tunnel. Females of ground-nesting species may dig complex, branching tunnels. To protect the developing bee and its food supply from drying out, excess moisture, fungi, and disease the cell may be lined with waxy or cellophane-like glandular secretions, pieces of leaf or petal, mud, or chewed-up wood. Some bees use clay to build walls between cells and to seal the entrance. Others cut round pieces of leaves which they use to line the inner walls of a tube.

Eusocial and Solitary Lifestyles

Most of Alberta’s native bees are solitary bees. Each adult female will build her own nest, then lay her eggs beside a ball of pollen and nectar which she collected herself. She has no worker bees to help her. When the egg hatches it becomes a larva, which will feed on this supply until it creates its own cocoon to protect the pupae stage of its life cycle. While in the pupae, it will transform into a fully grown adult bee. Most of Alberta’s solitary bees survive the winter as larva, and emerge as adults in the spring and summer. The adult female will not live to see her young become adults.

Some solitary bee species will nest in aggregations, though each nest is built and maintained by a single bee. In Alberta, ground-nesting bees in the genera Andrena and in the family Halictidae may exhibit communal behavior. in some species, the bees may exhibit semisocial behavior, where females cooperate to dig nests and provision offsping.

In Alberta, bumble bees are the main exception to this solitary lifestyle and are a primitively eusocial bee. That means that related individuals will cooperate to forage for food, raise young and defend the nest. A Queen bumblebee will build her nest then lay a batch of eggs which she will nurture to adulthood. She will forage for nectar and pollen, and will have pollen-carrying structures like her daughters. Once those bees are mature, the queen (mother bee) will stay in the nest to lay more eggs. Her daughters will build additional nest cells and provide their younger sisters (and some brothers) with pollen and nectar. Late in the summer, all bumble bees except the new queens will die. These new queens will mate, and they will survive the winter to build a new nest in the spring where each queen will raise her young.

The non-native honey bee is a highly eusocial bee, where there is a sharply defined division of labour between egg-laying queens and pollen-collecting workers. Queen honey bees are much larger than honey bee workers and have a greatly expanded abdomen. Since queens do not forage, they lack pollen-collecting hairs and could not survive without the aid of the workers. Honey bee colonies have multiple, overlapping generations of bees working together in nests that can last for years.

Cuckoo Bees

All the major bee families have species of cuckoo bees. These parasitic bees do not provision or make nests for themselves. Most of these species are cleptoparasites, which invade the nests of another species of bee, where it lays its egg near the pollen loaf the host bee made for its own young. The cuckoo bee larva will then kill the host’s young and feed off the stolen pollen store. In other cases, a social parasite such as the bumble bee cuckoo bees, will kill the host queen and the cuckoo bee’s young will be nurtured by the host queen’s daughters.

Because the young of cuckoo bees feed on pollen and nectar collected by the host bee, cuckoo bees don’t need to gather pollen to provision the nest. As a result, they have lost their pollen baskets and much of their hair, and many of these bees look like small wasps.

Seasonality

Alberta’s native bees have different strategies for surviving winter. Most halictid (sweat) bees and bumble bees overwinter as mated adult females, emerging in the early spring. Other species spend the winter in natal cells, either as un-mated adults or pre-pupae and emerge to mate as adults in the spring. The timing of emergence after wintering influences which flowers are important to a species. Early-emerging species, like many Andrena bees, visit early-blooming flowers such as Salix (willow) and Taraxacum (dandelion) and are only seen for a few weeks in the spring. Other species will be active for relatively short periods in mid or late summer when their preferred flowers are in bloom.

Feeding

Bees diets are specific – mostly pollen and nectar and a few bee species feed on floral oils. Bees can be found wherever their preferred host plants and suitable nesting habitat occur.

Some bees are very fussy eaters and will feed only on pollen from a single species of flower (this is called oligolecty). These types of bees are particularly susceptible to habitat changes and loss of the native flower species on which they depend. In particular, many species of Perdita, Dufourea, Diadasia and Macropis are oligectic, collecting pollen or floral oil on a very narrow range of flowers.

Other types of bees will feed on a wide range of flower types (polylectic). Bees’ bodies, particularly their tongue lengths, are adapted to different flower forms. For example, a bee that feeds on tubular flowers (e.g., Penstemon) will have a long tongue, but bees that like flat flowers (e.g., dandelions) will have a shorter tongue.

Aside from cuckoo bees, all female bees build nests, stocking them with a nutritious mixture of pollen, nectar and saliva before laying their eggs, and usually sealing them so the eggs and larva are protected from predators and moisture.