Specialist Bees

Ground-nesting female Colletes. Photo: Nicole Gerjets

While a beehive may be what many think of when talking about bee nesting, hives are specific to honey bees (Apis mellifera), a non-native species to Minnesota. Eusocial bees like honey bees and bumble bees are highly social with large colonies that cooperate to take care of young - with one queen and many specialized workers. High sociality allows colonies to grow large quickly, but these close quarters can facilitate spread of disease and pests.

In contrast, solitary bees, which make up 90% of bees globally, nest as individuals. Every adult female creates their own nest to lay eggs and provision for their young. All females can reproduce and there are no workers like in honey bee or bumble bee colonies. Often, a large group of solitary bees will nest in aggregations – these are not colonies, but rather, many individual nests that individual females tend to. Some bee species fall somewhere in-between highly social and solitary. These semi-social bees may have numerous females from overlapping generations work together with a single a nest entrance but with females taking care of their own brood.

Nearly 70% of native bee species nest underground. These may be found in turf but are more often on bare, exposed ground. They resemble ant hills with a slightly larger entrance hole and sometimes you can peak in and see a bee. Nests may be anywhere from several centimeters to up to a meter or more deep in the ground.

About 30% of native bees nest as solitary individuals in cavities, usually hollow stems, abandoned beetle borer holes found in dead trees, or stumps. While some can chew cavities with their jaws like carpenter bees, many depend on beetles for their nest cavities. With so much diversity in nesting and foraging habitat needs, providing an abundance of diverse flowers from spring to fall will help local bees forage throughout the summer. Dead wood and wood boring insects, two things we tend to get rid of in our yard or landscapes, are highly important for cavity nesting bees. Plants with pithy stems, like sumac, blackberry, elderberry, are also important nesting sites

Solitary bees emerge at various times of the summer depending on the species. In general, once an adult female emerges, it will start making a nest either underground, in a hollow stem, or in another natural cavity. The bee will mate and forage for pollen outside the nest, returning to it to create a mass of pollen known as a pollen ball. On this pollen ball, a single egg will be laid and then closed off, creating a cell, like a room, where the egg will turn into a larva and pupa all while feeding on the pollen mass before emerging to spend a few weeks as an adult the following year. These cells are provisioned one by one and the number of cells varies by species.

Identification and bee terminology

Some bee species can be identified using photographic evidence without the need to collect specimens, but many other species require viewing under a microscope by trained experts. Bees are diverse and often tiny, but these aren’t the only challenges encountered when trying to identify them. Identifying characteristics such as the texture of the exoskeleton, type and location of hairs, and even the number of “teeth” can only be seen with magnification.

Many specialist bees are best identified in conjunction with their host flower, though a positive identification of most species without microscopic features is unlikely. These pages aren’t intended to be used for species-level identification although with practice, many genera can be recognized in the field. Citizen science networks such as iNaturalist, Bumble Bee Watch, and BugGuide.net may help you report and identify bees through photo-sharing.