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The Fragile Future of Solitary Bees

Honeybees are important pollinators, but what about native, non-hive bees? It turns out that we couldn't live without these tiny creatures.

By Sarah Jay
Sep 9, 2021 11:00 PM
solitary bee
A male Osmia rapunculi bee looks out of an insect hotel. (Credit: Timelynx/Shutterstock)


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Honeybees seem to have the best public relations team — they’ve won the affection of many and eclipse our focus on other bees. And although we rely on the western honeybee for agriculture, they manage just a third of the pollination necessary for U.S. food production. In reality, around 80 percent of the worlds’ pollination lies in the legs and mandibles of native bees. This means that the world's agricultural industry couldn't operate without them.

They’re directly involved in native plant reproductive cycles, too. In fact, we can thank native plant pollinators for our food crops. Among unsung pollinators like wasps, flies and moths there are native bees — specifically solitary species — working hard to help native plants reproduce. They are among the essential workers of our ecosystem. 

Why Native Bees Matter  

Solitary bees, like carpenter bees, sweat bees and leaf cutters, pollinate the vast majority of native plants. Such flora attracts and hosts pollinators in gardens and yards. With their help we can grow the squash, peppers and other fruit we love so much. By pollinating native plants, solitary bees also maintain the harmony of the ecosystem.  

Without them we’d face ecological collapse. These dedicated insects work tirelessly and contribute directly to plant biodiversity, which supports the ecosystems we inhabit. Without an abundance of different organisms, natural systems lose their balance and confront pest infestations, unmanageable water resources and polluted air. Ultimately, species collapse and extinctions follow. Different risk factors — including our obsession with lawns — contribute directly to the decline of native species, including the precious solitary bees. 

While western honeybees ensure that we have food, they rely on our native pollinators to make it in the world. Solitary bees benefit from native landscapes, which support a healthy soil biome that sequesters carbon. Not only do solitary bees like nearby natives, but social bees like honeybees and bumble bees do too. 

A Delicate Upbringing 

Solitary female bees build nests in their preferred material. For carpenter bees, that’s untreated wood. Plasterer bees like a sandy hole in the ground. They mate with a male in fall and lay eggs within their hovels. Male eggs are placed close to the front of the nest, and female eggs behind because they take longer to develop.  

The eggs hatch in late fall, and bees feed their larvae with ambrosial mixtures of nectar and pollen. Bee larvae wait out the winter to emerge in spring as fully grown bees — males first and females second. Each goes on to carry their genetic material to the next generation. 

Because solitary bees lack a hive to protect, they don’t swarm. Some don’t even have stingers. Most are docile, genial creatures that prefer to carry on their work rather than get into a tussle. 

The most delicate aspect of solitary bee life: the larval stage. Several outside factors can  harm this phase of development. For example, scientists have shown in lab experiments that fungicides can slow larval growth. They also found that insecticides may impact the reproductive success of our solitary bee friends. Both fungicides and insecticides are commonly used in urban gardening and large-scale agriculture.  

Climate change also negatively influences solitary bee larvae, which require specific environmental conditions to succeed. As the planet warms, earlier springs can slow development as larval bees settle in for winter.   

So, what can we do as individuals to foster a more welcoming environment for solitary bees? Of course, the weight of the climate crisis isn’t ours to bear individually. But when possible, it helps to grow native plants in your home landscape. We can also build solitary bee homes specifically catered to an area’s native species. Bee houses work in conjunction with native plants to support a safe and nourishing environment for our gentle neighbors.

Introverts or Congregates 

Do all solitary bees live a hermit-like existence, flying solo all their days? The name seems to imply so. But the reality is much more nuanced, and different social structures exist among different species. Truly isolated species habitats consist of one female who builds a nest separate from others. There’s also aggregate species, who gather nests in one area with individual entrances. Or consider communal bees, who share an entrance to their personal nesting areas. Some are even semi-social and cooperate within the same nest to rear offspring.  

Want the buzz on solitary bees in your hometown? Here’s a few of the most common in the United States:

Mason bees include around 150 different species, the majority of which are native. Their size ranges from around 0.4 to 0.6 inches, and their colors vary widely across types. In the wild, they nest in tunnels of pithy plants hollowed out by borer beetles and moths.   

Plasterer bees are ground-dwelling bees. They look a lot like the western honeybee but have pale yellow bands rather than bright yellow ones. Females dig nests in areas with loose, well-draining soil. They range from 0.3 to 0.6 inches long, and their colors are uniform across species.   

Digger bees are like plasterer bees in that they nest in well-draining soil. However, they’re generalists and dig into other materials too. When they nest in the ground, they create small mounds with holes that open to the surface. Their size ranges from 0.25 to 0.5 inches, and their colors vary greatly from metallic to black and white, black and brown, or black and red.  

Sweat bees consist of over 500 species working hard across the country. Some nest in the ground, and some live in rotten wood. They are anywhere from 0.25 to 0.75 inches long and are monochromatic. They can be black, brown or metallic green.  

Carpenter bees are named for their tendency to burrow into untreated hardwood. They sometimes re-inhabit a nest previously used by another carpenter bee. Sometimes, they make their own. They’re the largest native solitary bees in the country, and range from 0.5 to 1 inch long. Their colors are your typical yellow and black to metallic black or green.  

So, look around for solitary bees. Be gentle with them. They have been gentle with us. 

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