Andrena Bees

Closeup shot of a female Andrena Tibialis bee sitting on leaf
Andrena Bee Classification
Class: Insecta
Order: Hymenoptera
Family: Andrenidae
Genus: Andrena

Andrena is one of the largest genera of insects, including more than 1,500 species.[1] The Andrena genus consists of medium-sized bees that nest in the ground, hence their common name “mining bee” or “digger bee”.[2] Their scientific name is derived from an ancient Greek word meaning “hornet” or “wasp”. 

As a taxonomic category, Andrena is a genus, which falls below families and above species. Andrena is a member of the family Andrenidae, which belongs to the order Hymenoptera. All Hymenopterans belong to the class Insecta. 

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    Where Can Andrena Bees Be Found?

    Andrena bees are found in temperate areas of the northern hemisphere, including Europe, Asia, and North America.

    There are fewer Andrena bees in tropical regions, but they can be found in semi-tropical and temperate areas of Africa. Andrena bees do not appear in South America or Australia.

    Since Andrena bees live in such temperate climates, they are very hairy to protect themselves from the cold. Andrena bees can be found in Scotland, Wales, the United States, and Canada. 

    Due to their wide range of habitats, Andrena bee species are frequently encountered by people living in cool temperate climates.

    How to Identify an Andrena Bee

    Andrena bees are commonly identified by their size and colour. The female Andrena bee ranges in size from 8 to 17 mm, while the male is slightly smaller.

    It is most common for Andrena bees to be black with white or light brown highlights on their abdomens and faces, although they may also be green, metallic blue, or black without bands.

    There are typically two or three submarginal cells on the wings of Andrena bees, which describe the way the veins in the wings divide the wings into sections. [3]

    andrena mining bee collecting pollen and nectar from white flower
    Andrena bees are very selective when it comes to feeding. They only feed on certain plants, and some species will only feed on one type of plant.

    There are large, distinctive foveae on the faces of female Andrena bees, which are grooves under bands of hair that appear along the inside edges of their eyes.[4] These grooves are similar to the eyebrows of people.

    The female Andrena bee also has hair on its hind legs for collecting pollen. Additionally, female Andrena bees always have a ring of hair at the bottom of their faces. 

    Several species of Andrena bees possess pollen pouches on their thoraces.

    Where Do Andrena Bees Live?

    Andrena bees live underground and can dig as deep as 18 inches.[5] The Andrena bee is a solitary bee, which means that it does not live in hives or have a queen. [6]

    Andrena bees dig their own nests in which to live and store pollen and nectar. A number of species of Andrena bee live in communities or aggregations, which means that they build their nests close to each other. [7]

    It is common for some species of bees to nest communally, in which case female Andrena bees share an entrance, but build their own nests.

    It is not uncommon for Andrena bees to build their nests in preexisting holes left by chipmunks and other rodents. It is common for some species of Andrena bee to arrange their brood cells in symmetrical patterns while others do so randomly.

    While some Andrena bees live close to the surface of the ground, others dig very deeply into it.

    The females of Andrena bees prefer to dig nests in sandy soil after mating. It is possible to identify Andrena bee nests by the piles of dirt and small holes that appear in the ground when the bees dig their burrows. The holes are approximately the size of a pencil.

    andrena mining bee female in nest
    Although the Andrena bee is a solitary species, it is common for them to nest communally, which means they have their own nest but share an entrance. A single nest entrance may lead to many Andrena bees.

    In order to protect their larvae, Andrena bee females line their burrows with waterproof material. As soon as it dries, the female Andrena bee rubs it with the tip of her abdomen to polish it and make it more stable. As a result, the larvae are protected from moisture.

    Andrena bees live underground, which makes them vulnerable to farming practices such as plowing and spading. 

    Andrena bees choose their habitats based on the availability of clear land and, in particular, the presence of berry bushes and fruit trees. Considering the importance of bees as pollinators, it is imperative that bee habitats are protected.

    Insecticides and pesticides pose a serious threat to all bee species, including Andrena bees. It is recommended that gardeners and property owners avoid the use of pesticides and insecticides in order to maintain a healthy lawn and garden. 

    The most effective way for homeowners to help Andrena bees survive is to have a garden full of orchids, berries, and fruit trees with plenty of bare soil.

    What Do Andrena Bees Eat?

    red female Andrena Fulva mining bee
    Andrena bees come in many different colours, like this red-backed Andrena Fulva female

    Adult Andrena bees eat nectar, and Andrena larvae eat both nectar and pollen.[8] Some species of Andrena bee are willing to feed on several different flowers, while others are very specific about what flowers they visit. Most Andrena species prefer to feed on blueberry bushes, fruit trees, and orchids. 

    Almost all solitary bees including Andrena bees are oligolectic, which means that they select very specific plants to feed on. Some species of Andrena bees are monolectic, meaning that they feed on just one specific species of plant. 

    This makes Andrena bees vulnerable to extinction, since they are so selective about what plants they feed on. If the plant that they prefer becomes unavailable, Andrena bees cannot feed on any other plant and may die off. 

    Depending on what plants they prefer to feed on, Andrena bee species have a variety of morphological adaptations to make their feeding more effective. 

    Some Andrena bees have longer hairs than others, and some have pouches on their thoraces to store pollen. Most species collect pollen on the upper parts of their hind legs. 

    Andrena bees feed in the spring as they are getting ready to lay their eggs and raise their larvae. Before Andrena lay their eggs, the bees eat primarily nectar. Then, once the eggs are laid, they begin collecting pollen with which to feed Andrena bee larvae. 

    Do Andrena Bees Pollinate?

    Andrena bees are key pollinators of blueberries, raspberries, orchids, and fruit trees. Andrena bees pollinate plants by flying from one to another, transferring pollen from one plant to another. It is not an intentional act on the part of Andrena bees; it is a supplemental effect of their travels between the plants.

    Andrena bee females make more visits to plants than males in order to feed their larvae, making them more effective pollinators.[9] Additionally, because female Andrena bees are larger than males, they carry more pollen from plant to plant.

    Male Andrena mining bee on blade of grass
    With plenty of hair on both their bodies and hind legs, Andrena bees are well equipped for pollination.

    Andrena bees collect pollen by buzzing the flowers, which releases pollen. Generally, Andrena bees feed on and pollinate fruit trees, orchids, and blueberries.

    The Andrena bee is an excellent pollinator due to its ability to collect its own nectar. Even though male Andrena bees do not intentionally collect pollen because they do not have to feed larvae, they still pick up some when they visit flowers and can transfer it between flowers.

    Do Andrena Bees Make Honey?

    As Andrena bees are solitary, they do not produce honey. The lifespan of bees in the Andrena genus is devoted exclusively to reproduction and feeding their offspring. As a result, Andrena bees do not attract animals like bears or skunks that feed on honey.

    Do Andrena Bees Sting?

    male andrena mining bee foraging on the ground

    It is rare for Andrena bees to sting since they do not have honey to protect. Typically, Andrena bees are not aggressive in nature. 

    There are no stingers on male Andrena bees, and the stingers on female Andrena bees are generally too small to penetrate human skin.[10] All species of Andrena bees have this characteristic.

    It is possible to be stung by a female Andrena bee if it is accidentally squashed or scared, but this is extremely rare. By staying away from their nesting area and not provoking them, people can avoid being stung by Andrena bees.

    Despite the fact that an Andrena bee might attempt to sting, if the person being stung brushes them off and walks away, they will be able to avoid being stung. 

    Due to its non-aggressive nature, Andrena bees do not follow people and attempt to sting them in the manner of other species.

    How to Get Rid of Andrena Bees

    To get rid of Andrena bees, it is recommended that lawns be watered regularly or that any areas where they may nest be mulched. 

    Because Andrena bees prefer clear, sandy, and dry areas to nest, they will find another place to nest if lawns are kept moist or covered with mulch.

    Andrena bees are sometimes blamed for creating bare patches in lawns. The most likely scenario is that the bare patches already existed, and the bees chose to nest there since they prefer to nest in exposed, dry soil without grass.

    Considering the importance of Andrena bees as pollinators and the fact that they do not pose a threat to humans, removing them is not recommended.

    Reproduction & Lifecycle of Andrena Bees

    There is only a very short lifespan for Andrena bees during the spring, with their lifespan being approximately four to six weeks. An Andrena bee has one generation per year and hibernates during the winter as an adult, emerging in the spring when temperatures climb. [11]

    When Andrena bees emerge from hibernation, the males emerge first. Thereafter, the male and female Andrena bees mate. Female Andrena bees are attracted to males by the pheromones that they carry on their faces.

    It is pertinent to note that all of the female bees in the Andrena genus are fertile. This is in contrast to many other species of bee that have sterile worker bees and a few fertile queen bees.

    The male Andrena bee dies shortly after mating. In the following weeks, female Andrena bees dig their nests in sandy soil, lay their eggs, and collect pollen and nectar for their larvae.

    Female andrena mining bee sitting on flower
    To protect the larvae of Andrena bees during the reproduction cycle, the females line their burrows with a waterproof material.

    Pollen is collected by the female Andrena bees and used to create small balls that are used to feed its larvae. Andrena bee eggs are laid in small cells lined with a waterproof substance that they secrete. During their life cycle, female Andrena bees provide nectar and pollen for their larvae.

    When Andrena bee larvae pupate and become adults, they remain underground until the following spring. The adults of Andrena bees hibernate in their nest cells over the winter and emerge when the temperature rises, resuming their life cycle.

    Male Andrena bees emerge first from hibernation, attracting females with their pheromones, which leads to mating and the continuation of the life cycle. From March through June, Andrena bees can be observed, and they live for a short period of time.

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