How to Support Your Solitary Bee Population

Solitary Bees Play a Critical Role in Pollination

How to Support Your Solitary Bee Population

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There are more than 20,000 species of solitary bee. Native to nearly every corner of the globe, they are adapted to a vast diversity of climates and habitats.

By Leah Grunzke – Bees are profoundly important to our larger ecosystem. And yet, many of us are only familiar with a tiny branch of the bee family. There is a rich depth to the world of bees, with an incredible diversity of unsung heroes — solitary bees — waiting to be discovered.

Honey Bees and Bumblebees Form Social Colonies

We are all familiar with the charismatic honey bee — the poster child of the Hymenopteran family, which includes bees, wasps, ants, and termites. Honey bees are social insects with highly structured colonies. Queens, drones, foragers, guards, nurses, builders and so on; each individual plays a key role in collectively raising the hive’s brood. All honey bees, whether in managed hives or wild colonies, are of the species Apis mellifera, imported to North America from Europe in the 1600s for use in honey production and later, crop pollination. While certainly, the most famous, A. mellifera is far from the only species of bee in the world.

Bumblebees are also beloved and familiar to most of us. Bumblebees, like honey bees, form social colonies to collectively raise their offspring. There are about 50 species of bumblebees (Bombus sp.) native to North America, where their large bodies are well adapted to the cold northern climates. They’re important pollinators of Solanaceae plants – potato, tomato, pepper, petunia, and many others.

Aside from honey bees and bumblebees, most bee species are solitary creatures, raising their young in individual nests much like the rest of the animal kingdom.

Understanding Solitary Bees

There are more than 20,000 species of solitary bees. Native to nearly every corner of the globe, they are adapted to a vast diversity of climates and habitats. More than 4,500 species are native to North America, with the number ever growing as new species are discovered and identified.

These bees range from the size of peppercorns to over an inch long. Some resemble their honeybee and bumblebee cousins; others look like wasps, houseflies, or winged ants. Some people ask: Do solitary bees sting? They don’t make honey, and without a hive to defend, they rarely if ever sting.

Solitary Bees include Mason bees, leafcutters, carpenter bees, miner bees, sweat bees, and others. Solitary bees are largely docile and overlooked, but they play a critical role as pollinators.

Three-quarters of native bee species dig tunnels in the ground to build their nests. The rest find nooks and crannies to lay their eggs in — woodpecker holes, beetle tunnels, even crevices in buildings. Life cycles of different species vary but follow a pretty consistent pattern.

How Long do Solitary Bees Live?

In temperate climates, solitary bees emerge in spring and summer. Males are the first to come out, and wait nearby for the imminent rush of females. The male’s life outside is short and sweet; he’ll spend his entire life mating and be gone within a week or so. Females live closer to six weeks, and get to work immediately building and provisioning their nests.

Brood cells

After finding a suitable tunnel or cavity (maybe the one they just emerged from!) they start by laying an egg. A bundle of food is tucked along with it —pollen for protein and nectar for carbohydrates. The lot is wrapped in a protective cocoon and sealed off into an individual cell using mud, leaves, tree resin or other natural materials. Each female will build 10-20 of these brood cells over the course of her life. The eggs inside hatch into larvae, and later pupate into their adult form. The young bees overwinter in their sheltered nests and emerge the following season to start the process anew.

Solitary bees are incredibly efficient foragers, whose importance as pollinators cannot be overstated.

A single mason bee may pollinate 50,000 flowers in a season.

With their enormous diversity in species, there are wild bees adapted to fill a vast array of ecological niches. There are species that emerge very early in spring, or are most active late in the season, covering a wide range of bloom times. Being native to their region’s climate, they’re able to withstand weather conditions imported honey bees may not. Solitary bees are the exclusive pollinators of some plants, like alfalfa, and critical players for others like melons, stonefruits, legumes, and the bulk of native flowering plants. Not only do solitary species play a key role in many of our food crops, they are also responsible for pollinating the plants that wild animals, rodents and birds feed on. Without wild bees, our native plants and the herbivores they support would be in serious trouble.

Mason on a Pasque flower

Solitary Bees are Under Attack

Solitary bees face some of the same threats to their population as honey bees do. Parasites and disease can be a problem, as can the widespread use of toxic chemicals in the environment. Climate change is creating subtle shifts in breeding and bloom seasons that have far-reaching impacts. And loss of habitat is perhaps the single biggest threat to wild bee populations. Large expanses of ecologically barren grass lawns, urban sprawl and city planning that doesn’t prioritize green space all result in a loss of the floral biodiversity and suitable nesting sites critical to these essential insects’ survival.

Miner bee

How to Support Native Bee Populations

Whether you live in a rural or urban setting, there are simple steps you can take to support native bee populations.

  • Use caution and restraint with chemical fertilizers or pesticides. They are often unnecessary and toxic to beneficial insects.
  • Maintaining lawns is expensive and time-consuming. Consider converting turf areas to biodiverse landscapes that provide food for pollinators.
  • Wild gardening mimics nature, and nature can be untidy. Provide shelter and nesting materials withstanding snags, brush piles and natural, permeable mulch. Leave some soil bare to encourage ground-nesting bees.
  • Don’t forget water! A pie plate filled with stones provides a perch for insects to take a drink without falling in.
  • Plant a diversity of flowering plants, opting for species native to your area rather than hybrids or imports. Aim for variety in flower color, shape and bloom times. Bees love blue and white flowers, tubular blossoms and wide landing pads like those in the sunflower family.
  • Pay attention to the shoulder seasons, and choose plants that flower in early spring and late fall when other pollen sources are scarce.
  • Educate your urban planners! Rooftop gardens, pollinator-friendly roadside plantings and native landscaping in parks are all meaningful ways to support wild bees in the city.

The world of bees is wide and full of fascination. Resources like The Xerces Society and Pollinator Partnership provide many opportunities to learn more, and programs like The Great Sunflower Project and Insight Citizen Science let you get involved and contribute valuable data on these under-studied insects. Happy bees make a happy world, so keep learning!

Build Your Own Bee House

“Insect hotels” readily attract mason bees, leafcutters, and other cavity-nesting species, and are a fun way to observe solitary bees up close. Houses for bees may be elaborate or very simple; just remember these tips to create your own!

  • Provide tubes made from paper straws or hollow plant stems. Bamboo works great, but you’ll find hollow stems in a wide variety of garden perennials, especially plants in the carrot family. Tube diameter should be around 1/4-1/2″. Cut tubes to be at least 4″ in length, but not longer than 8″. This ensures females will lay enough of both male and female eggs to support the population next season.
  • Place tubes in a sturdy frame with a back on it. Instead of tubes, you can also choose to drill holes in a block of wood using a 3/8″ bit. Cedar is said to repel insects, but most other untreated scrap wood will work fine. Avoid toxic paints and varnishes and instead brush on mineral oil, which gives an excellent protective finish to tube frames and drilled blocks.
  • Hang your bee box facing east toward the rising sun, in a spot with some protection from heavy winds and rain. Cover the front with small-gauge chicken wire if woodpeckers are a problem; their long tongues can reach deep into the cavities where young bees are developing.
  • Native bees are adapted to your local climate, so there is no need to take your nesting box inside for the winter. To avoid buildup of pests or disease, replace old tubes and clean out drilled holes with a pipe cleaner dipped in a 5% bleach solution every couple of years.
  • Provide plenty of bee-friendly plants for forage, then sit back and enjoy watching your busy native bees at work!
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