All about Mining Bees

Mining bees, scientifically known as ‘Andrena’, belong to a large group of solitary, ground-nesting bee species. Andrena is Greek and means as much as ¨buzzing insect¨. Other names include Bare-Miner Bees, Fairy Bees, Oxaeine Bees, Burrowing Bees, Digger Bees, and Andrenids. These friendly little creatures are non-aggressive and usually do not sting or bite.

The decline of native pollinators, such as mining bees, is a concerning issue as they play a vital role in nature and agriculture. They are essential for plant reproduction and provide a number of ecological services. They also provide valuable pollination services to crops, which is especially important as the use of honeybees for crop pollination is becoming more costly and less reliable due to disease, parasites, and environmental conditions.

The Missouri-endemic mining bee species Andrena beameri is currently listed as vulnerable to local extinction. It has very specific habitat requirements. In order to survive, it needs early-blooming Coreopsis species that only grows in the prairie and only blooms a few weeks during the year. Consequently, the conservation of prairie remnants is essential in order to preserve the Andrena beameri species.

How to Identify Mining Bees

People often mistake them for honeybees or wasps. However, miner bees have a distinct look compared to other bee varieties. They are usually dark, often with bands or stripes. Depending on the species, they can be more or less hairy.

Experts can recognize this bee family by their distinctive characteristics. These include dense bristles (scopae) at the legs’ bases, shin-like tibias on the legs, creases and grooves on the face and head, and unique vein patterns on their wings.

Members of the Andrena genus have distinctive facial features. They have a narrow stripe of pale hairs on either side of their face that runs downwards and helps to protect the eyes. It originates from a groove (fovea) between the compound eyes and the center of the face.

Some mining bee species boast significantly large compound eyes, as well as ocelli positioned between the compound eyes or on the forehead. These big-eyed species are usually active only during the twilight hours and as a result, they’re well-suited to act as pollinators of evening primroses or other flowers that typically flower at dawn or dusk.

The large eyes of these bees allow them to navigate in dim light conditions, which is especially important during the hours of dawn and dusk.

Adult Mining bees are small in size, about: ⅜–¾ inch (1 – 2 cm). Some, like the genus Perdita, are smaller than 0.1 inches (2.5 mm). This makes them one of the tiniest bee species in the world. These mining bees may be small, but their contributions to ecosystems are invaluable.

Mining Bee Habitat

Mining bees are common to temperate regions of Asia, Europe, and North America including Mexico, with the biggest diversity found in the Mediterranean climate. Although a few species live in sub-Saharan Africa, there are non in South America, Australia or Madagascar.

An estimated 400+ species of Adrena bees live in North America. Most are found in the US desert southwest and Great Plains due to the diversity of special flowers and the dry, sandy soils. Generally, mining bees, as the name suggests, prefer ground-nesting habitats. They like to establish their home in well-drained soil, such as clay, fields, dirt roads or grasslands but are also found burrowing between stones of old buildings. It is also possible to enticed them to nest in home-made nesting blocks, like a bee hotel.

Their nesting sites often depend on their subspecies. For instance, the Ashy mining bee (Andrena cineraria) prefers to nest in sloping areas. The Grey-patched mining bee (Andrena nitida) favors flat formal lawns and sheep-grazed hillsides. They also like mounds of soil that resemble worm casts, or holes in bare patches.

Tips to Observe Mining Bees

To observe a specific species of mining bee, research which flowers they utilize as their primary food source. Find out the time when those flowers bloom and where they are commonly found.

Another alternative to finding mining bees is to look for places where they nest. They generally prefer to nest in sandy or dry soil with little vegetation. This could be fields, dirt roads, hiking trails, or grasslands. Nests are typically identified by a small pile of dirt near the entrance, or the female conceals the entrance with a leaf or some other material.

Nesting Habits

Mining bees often nest in aggregations. This means although a number of other mining bees nest in the same location, each female has her own nest. The individual nests typically branch similar to mole tunnels and can be between 1 and 2 feet deep (30.5 to 61 cm). Each individual branch contains one brood cell with a ball of provisions containing pollen and nectar at its end to feed the larvae. Some Andrena species secrete a sticky substance they use to waterproof the walls of each cell. Once the egg is laid onto the provisions, the cell is sealed and work continues on the next branch.

The timing of when exactly mining bees emerge is still somewhat of a mystery. With only one brood annually, they rely on the blooms of specific flowers to feed and reproduce.

Most of these specialized pollinators have a life cycle that is precisely coordinated with the flowering of particular plants. They are some of the earliest pollinators to spring into action before other insects emerge, with many species active as early as March and April. Many of these mining bees have a close relationship to particular wildflowers. They time their emergence precisely to coincide with blooming season, and can be spotted busily collecting nectar, even if there is still snow on the ground.

Furthermore, due to the differences between species in terms of habitat preferences, some bees may emerge earlier than others to take advantage of the available resources. Scientists have also identified a few other factors, such as temperature and available food sources, that can influence the emergence of these bees.

Why are Mining Bees so important?

In the U.S., around 30 % of crops rely on native bees for pollination. Mining bees and other native bees pollinate wildflowers, fruits and vegetables, and a variety of other crops. These pollinators are often specialists that evolved alongside specific types of plants. This means they are the only insects capable of pollinating them. Without them, the plants cannot produce seeds and reproduce. In addition, the seeds, fruits, and the plants themselves also serve as food for countless animals. This makes pollination critical to life as we know it.

Predators of Mining Bees

Miner bees fall into the category of short-tongued species. This makes them a prime target host for cleptoparasitic genera Nomada (nomad bees). Other predators include birds, and parasites such as certain flies, blister beetles, and tiny wasps (Montodontomerus sp.). Moving nesting blocks into unheated sheds or garages once they become inactive until early spring may help to protect the mining bees. Larger predators include racoons and opossums, which are known to dig up and consume the prepupae and pupae.

Sub species of the Andrena Genus

Worldwide, there are estimated to be more than 1,500 known species of mining bees. The Andrena genus has a large variety of subspecies. Each of these species has adapted to different environments in order to survive and thrive. They include the Chocolate Mining Bee, Ashy Mining Bee, Orange-tailed Mining Bee,Grey-backed Mining Bee, Red Girdled Mining Bee, Grey Patched Mining Bee, Painted mining bee, Short-fringed Mining Bee, Heather Mining Bee, Tawny Mining Bee, Grey-banded Mining Bee, Large Scabious Mining Bee, Buffish Mining Bee, Sandpit Mining Bee and others.