Spring has come around again, and your garden seems to be humming from the ground up. New life abounds in the plant and animal kingdoms, and the miner bee family is no exception. These tiny insects have emerged from the nest, ready to do their bit for the future generation of miner bees, simultaneously pollinating some of our plants.
Miner bees belong to Andrena’s genus of bees within the Andrenidae family. They are smaller than honey bees and have plump, furry bodies. With around 1500 species and 104 subgenera, they form one of the largest categories of solitary bees. The miner bee is known as Anthophora abrupta.
It’s mind-boggling to think that there are so many species of just one type of bee. All these little insects nest in the ground and have many similar characteristics. But there are differences between the different species as well. As we dig deeper into the life of miner bees, we will again stand in awe of nature’s ingenuity.
What You Need To Know About Miner Bees
Mining bees are categorized as solitary bees. These bees are loners and do not belong to colonies. The females build individual nests, but some solitary bees are gregarious, meaning they prefer to build their nests alongside other bees of the same species. There are 20 000 – 30 000 solitary bee species worldwide. Miner bees do not produce honey or fly in swarms to defend their nests.
Why We Call Them Miner Bees
Miner or mining bees are so-called because they make their nests in tunnels under the ground. They are also known as chimney bees because they build little turrets at the openings to their nests.
Description Of Miner Bees
With so many species of bees, miners can be challenging to identify. Some have vivid coloring, while others are dull and drab. Some are very hairy, while others have almost no hair at all. However, they are all similar in the way they mate and build their nests. All mining bees build their nests in the ground, digging tunnels to lay their eggs in.
They are often confused with bumblebees with their black and yellow bodies. The female is brighter in color than the male. Miner bees have brown-black hairs covering their heads, abdomen, and legs. The thorax has thick, pale yellow-orange hairs, and brown-black veins run through its almost translucent wings.
Female adults are usually 14.5 to 17mm long and have a prominent clypeus (the area between their eyes and mouth). Male adults range in length from 12 to 17 mm and are known as “mustached mud bees” because of the hairs on their yellow clypeus. This mustache contains pheromones that attract females.
The large velvety regions between the compound eyes and the antennal bases, known as face foveae, distinguish them from other bees. They mainly transport pollen on their femoral scopal hairs. However, many miner bees also have a propodeal corbicula (pollen basket) to carry pollen on their thorax.
The Life Cycle Of Miner Bees
Miner bees are only active for a few weeks every year, from March to May. Here is a summary of the life cycle of miner bees.
- Adult bees come out of their tunnels between April and June, depending on the climate in their particular location. The males always emerge before the females, sometimes up to five days before.
- The bees settle on flowers to mate. Males sometimes mate multiple times, but the females will only mate once.
- The first females born will survey the area for a suitable nesting site, such as a sheltered clay soil embankment. Females born after the established nesting location won’t look for a new one but will build close to the other nests.
- The female will start digging a tunnel in the soil. She will build chambers off the main tunnel, carry provisions to each compartment, and lay a single egg, sealing it up afterward.
- The eggs are white, measuring about an inch in length, and resemble slightly bent bits of rice. Larvae are lemon yellow when fully grown, measuring approximately half an inch in length.
- After five days, the egg hatches and the newly-hatched larva begins to eat the food and cell lining. The larva eats and grows for the following three weeks. It then defecates in the chamber at the end of this growth cycle and becomes a prepupa.
- After overwintering for nine-and-a-half months, the prepupa sheds its skin and becomes a pupa for approximately two-and-a-half weeks. Finally, the adult miner bee emerges from the tunnel, ready to take on the world.
- Usually, more males are produced than females, typically in a ratio of 2:1.
- The female mining bee lives approximately 4 to 6 weeks, while the male will only live half as long.
The Distribution Of Miner Bees
Miner bees prefer areas with Mediterranean-type climates. We can find them in the temperate regions of Europe, Asia, and North America. Southern Africa has a few species, but none are present in Australia and its surrounding islands, Madagascar, and South America.
There are 450-500 species of Andrenid bees in North America. Miner bees are vital links in the pollination chain, especially in the mid-west region. A. abrupta can be found from Texas to Florida and up the East Coast to Canada.
Where Miner Bees Build Their Nests
Miner bees generally nest in the ground, hence their name. Usually, they will nest in bare, firm sand, sometimes on steep inclines or vertical surfaces of hard clay or adobe. They generally prefer well-drained soil, such as clay. Some miner bees dig between the bricks of old chimneys built with non-mortar cement. We can also find them in log cabins and barns.
Sometimes mining bees will nest in groups, which could have 5-2000 bees in it. On occasion, and depending on the species, females may share a common nest tunnel entrance. However, each female will have her own nest and only provide for her own young.
Females of different species may have other preferences for nest locations. The Grey-patched mining bee fancies formal green lawns and hillsides where sheep graze. The Ashy mining bee prefers to make her nest on a slope.
If you’re walking in your garden and notice little piles of soil that look like worm casts amongst the grass, borders, and plant pots, you are probably walking through a miner bee’s nesting grounds. You may even see some holes in open patches of sand. Those miner bees have been busy.
How The Female Miner Bee Builds Her Nest
The female miner bee is a typical single mother! She has to build the nest, lay the eggs, and provide food while they are inside the nest. But that is where the similarity ends. When she finishes these tasks, she flies away or dies, and the new generation must take care of themselves.
- After mating, the female bee will begin making her nest in the soil by digging a tunnel.
- She uses a secretion from her Dufour’s gland to line the burrow and the turret. This fluid hardens into a wax-like substance that waterproofs strengthens, and smooths the tunnel’s interior surface. When it is about an inch deep, she will utilize the particles from inside to construct a turret above the entrance.
- The secretion will also provide nutrients to the mature larvae.
- On completing the main tunnel, the female begins to dig chambers to lay her eggs. There can be up to seven chambers off the main tunnel. She also lines these with the waterproof secretion.
- When she has completed a chamber, she collects pollen and nectar from nearby flowers, mixing with more of her secretion. This becomes a soft batter on which she lays a single egg. Then she seals the chamber with soil before moving on to the next one.
- When the female has laid the eggs and completed the chambers, the female makes a plug at the entrance to the tunnel. Between the plug and the first chamber is an empty space.
The Miner Bee’s Food
Like any other bee species, Miner bees are lovers of pollen and nectar that come from the flowers around their habitat. Species differ in their foraging preferences.
Some species of mining bees will eat from many different types of flowers. We call these little guys generalists. Others are picky eaters and will only feed on certain flower species. These are called specialists.
Occasionally the mining bees will extend their tastes to other genera within an individual plant family. Some specialists may only feed on flowers from one family or genus of plants. Bees that have these eating habits are known as oligolectic.
Mining bees play a vital role in flower pollination despite their diminutive size.Anthophora abrupta visits many flowers and is a forage-plant generalist. It collects pollen from many wildflowers that are indigenous to prairies and woodlands.
Some of these flowers include the following: Mead’s milkweed, Oenothera, Rubus, Rhododendron, Penstemon, Conrus, Asclepias, Iris, Monarda, Delphinium, Nepeta, Diospyros, Rosa, Melilotus, Trifolium, and Pastinaca.
A. abrupta also has the potential to pollinate many important crops such as tomato, cranberry, blackberry, persimmon, clover, raspberry, and blueberry. But pollinator management techniques have not yet been established for these miner bees.
Threats To The Survival Of Miner Bees
So many species of animals and plants are currently under threat, including the miner bee. Below are some of the factors that threaten their survival.
Human Advancement Threatens Miner Bees
As countries’ populations have grown and people are using up more land, all bees have to battle for food sources and habitat. As humans clear ground to build houses, shopping malls, and cities, we encroach more and more on the natural habitats of the mining bees. Flowers supplying pollen to the bees disappear from the area, forcing the bees to search for pollen elsewhere.
Competition For Food And Habitat Is A Threat To Miner Bees
Honeybees are not indigenous to North America. They were introduced to the country by settlers and are domesticated and managed for mass flowering crop pollination. Wild bees have to compete with managed bees for pollen and nectar resources. The presence of honeybee hives can reduce wild pollinator species, including the mining bee.
Pesticides Pose Significant Threats To Miner Bees
Neonicotinoids are highly harmful to bees. Farmers coat the seeds with them or spray them on the soil. These poisons then permeate the plant tissues and end up in the nectar and pollen. These substances disrupt memory and learning in many species, including mining bees.
Studies show that neonicotinoids affect reproduction. They decrease sperm viability, resulting in 30% fewer offspring. Farmers administer these poisons year upon year, which means that bees that consumed them as larvae would also collect poison-laden pollen and nectar during the following year. These bees lay 20% fewer eggs than those with only one dose of the poisons.
Predators Threaten Mining Bees’ Survival
Mining bees are vulnerable to predators such as birds, parasitic flies, tiny wasps, and blister beetles. Raccoons and opossums have sometimes dig up the nests and eat the prepupae and pupae.
Cleptoparasites Steal The Miner Bees’ Provisions
Cleptoparasites are critters that target the food that the host female has gathered for her offspring. The female cleptoparasite lays her eggs in the host’s nest, and her offspring feed off the supplies meant for the host’s young. Nomad bees target the nests and food of mining bees.
The Effects Of Miner Bees On The Environment
Mining bees sometimes get the blame for bare patches in between beautiful green lawns because some tunnels are visible. In reality, these little creatures would have selected the patch because it was already sparse. With such a short lifespan, they have no time to waste clearing the plot first!
While these little mounds of earth peeking out of your golf-course-type lawn may not be your idea of a picture-perfect garden, the bees are not harming the soil. They are aerating it.
Although these bees are solitary, providing only for their own nests and young, many species will build their nest in aggregations. This could give the impression that swarms of bees are invading your property, and many people fear getting stung.
Mining bees are not aggressive or dangerous. In truth, these busy little creatures are very docile and very rarely sting or bite, except in self-defense. The females have stingers, but even if they manage to penetrate the skin, the pain is minimal, only scoring a 1.0 on Schmidt’s pain scale. In rare cases, the bees may bite someone if they feel very threatened.
Mining Bees Are Important Pollinators
Mining bees play an essential role in pollination. The adults consume nectar and supply both pollen and nectar to their larvae (many are picky eaters of only a few plants). The female and male mining bees both source their nectar, making them a highly effective pollinating species.
Miner bees are “buzz pollinators.” They create a vibration that triggers plants to release pollen. Some of their favorite plants are apples, other fruit trees, different orchids, and blueberry/huckleberry plants.
While mining bee activity in early spring may frighten some individuals, they should be left alone to finish their long springtime to-do list. Mining bees’ spring activities assure their survival and the pollination of crucial food plants for people, insects, and animals.
Some people feel the need to remove the springtime mining bees and advocate Sevin dust or other pesticides. This is an absolute no-no as we depend on these and other bees and insects to propagate our food. We should be finding ways to perpetuate the mining bee and all the other species.
How To Attract Mining Bees To Our Gardens
If you’re a nature lover, you may be interested in drawing mining bees to your garden. Apart from planting the flowers that attract them, you could try using homemade nesting blocks. Although they take a week or two to dry out, they are quick and easy to make.
Follow these instructions to make a DIY nesting block for miner bees:
- Half-fill a five-gallon bucket with clay soil and add water until the bucket is full.
- Stir to create a thick, sloppy mixture.
- Let the slurry stand for a while to allow any sticks or leaves to drift to the surface.
- Skim the organic debris from the top of the mixture and pour off any excess water.
- Find an open styrofoam or wooden box measuring approximately 6 x 6 x 8 inches.
- Pour the remaining mixture into the box and allow it to dry. This can take days or weeks, and the box will shrink a bit due to moisture loss.
- Before the block has dried out completely, push some holes about 1 inch deep into the open side of the box. Make the diameter about 3/8 inch.
- Place the block on its side facing South or East, raising it 1-3 feet above the ground.
- Create some protection from the elements by putting it partly inside an open horizontal garbage can or another large container.
- Also, make sure that there is a shallow water source close by for the bees to collect from.
- Make sure your nesting blocks are ready by April when the bees search for great places to live.
- When the bees are no longer active, it may be good to move the blocks into an unheated shelter, such as a garage or shed, until the following spring. These little bees are susceptible to predators such as birds, tiny wasps, and certain parasitic flies.
Interesting Facts About Different Types Of Mining Bees
Although we have learned that there are more than 1400 species of mining bees, it is worth taking a quick glance at a few of them.
- The Chocolate mining bee is one of the bigger species of mining bees, measuring about half an inch. Because many nesting chambers share a single exit, many bees meet each other while trying to get out. Males want to mate immediately, with the result that females are often fertilized before they have seen the light of day.
- The Ashy mining bees dig tunnels up to 8 inches deep. They have the interesting habit of shutting the entrances to their tunnels when there is wet weather or when they are disturbed.
- The Grey-backed mining bee is said to be short-tongued. Although the length of different bees’ tongues is quite an involved biology lesson, short-tongued bees tend to mop up or dab at the nectar rather than suck it. The females also never gather nectar and pollen on the same days!
- The Heather mining bees are a small species that nest either completely alone or in very loose aggregations.
What To Do When You Have Miner Bees In Your Garden
When a specific patch of your garden seems to be over-populated with bees, all that buzzing could be quite intimidating. So what should you do?
The most eco-friendly thing to do is nothing! Leave them alone because it is highly unlikely that they will sting or bite you even if you walk across the nesting area on your (their) lawn. They will only be active for 6 to 8 weeks during the spring before disappearing for a year.
Under no circumstances should poison ever be used to get rid of miner bees or any other type of bees. Killing bees is detrimental to the health of our planet as it threatens our food supplies. We need them to pollinate our plants, or they will not produce the food we need.
Miner bees should not be considered pests. They are friendly, docile, and far too busy to bother stinging or biting people. They are active in the spring for 6-8 weeks, busily mating and building nests for the eggs about to be laid. The nests are cleverly constructed tunnels that the female builds on her own, adding chambers for each offspring. We owe mining bees a debt of gratitude when they nest in our gardens because while they are primarily concerned about procreating, they ensure that our food plants can reproduce. What fantastic little creatures! So instead of trying to eradicate them, we should leave them “bee.”