Nest boxes for mason bees

This very small bee was exploring the various nest holes in this bee box. This tiny bee is in the Tribe Osmiini, and in the genus Heriades (thanks to Bug Guide for identifying the genus).

This very small bee was exploring the various nest holes in this bee box. This tiny bee is in the Tribe Osmiini, and in the genus Heriades (thanks to Bug Guide for identifying the genus).

by Sandy Garland

Mason bees are named for their use of mud or clay in their nests. They belong in the genus Osmia in the family Megachilidae.

At the Fletcher Wildlife Garden, we have found Blue Orchard Mason Bees (Osmia lignaria) as well as the Heriades pictured below. This and other species in the family are very good at pollinating fruit trees. They are closely related to leaf-cutter bees, which will also use bee boxes.

Some sources of information about mason bees
Blue Orchard Mason Bee

Life cycle of mason bees

May: Adults emerge in spring around the time apple trees bloom. They mate and lay eggs, provisioning their tunnels with lumps of pollen mixed with nectar and saliva. They seal the
chambers and the whole tunnel with mud, so need a source nearby. Adults live 4‐8 weeks.

Early summer: Eggs hatch, larvae eat their pollen

Late summer: 5th instar larvae pupate

September: Pupae open and adults emerge, but hibernate in their coccoons until the following spring, when the cycle starts again.

Why do they need bee houses?

Mason bees do not dig their own tunnels; instead they look for “natural” tunnels, such as hollow plant stems or twigs or the abandoned nests of other insects. Many of these potential mason bee nests are cleared away from our urban properties in an effort to keep our yard “tidy.”

Bees are also susceptible to parasites and disease. Providing a nest box that can be cleaned or replaced every year may help minimize these and produce healthier bees.

Mason bees are readily attracted to paper tubes. Drilled holes in wood are also an option, but both types of tunnels should be replaced every year.

How to make a mason bee box

Our instructions come from Richard Scarth, who has been helping mason bees for many years. Jenny Sheppard demonstrated the construction of this type of bee box at a workshop in May and donated two boxes to the Fletcher Wildlife Garden.

Step by step instructions

Please note: this easy-to-make bee box is intended for summer use only. The idea is to open the tunnels in the fall and store cocoons in the refrigerator over the winter. This provides a chance to clean away parasites and increases the chances of bee survival.

Jenny has kindly offered to do a follow-up workshop in the fall to show us how to retrieve cocoons properly and the best way to store them.

Alternatively, you may wish to build a protective structure for your bee boxes and leave them out all year round. In either case, the whole box should be replaced in spring just before the previous year’s adults emerge.

Does it work?

We installed our two boxes in our insect hotel on 7 May 2015. Within a week, bees were busily filling the tunnels with nectar and pollen, laying eggs, and closing up the compartments with mud.

In this photo, taken on 15 May 2015, two tunnels in our bee box are already full of eggs and are sealed with mud. A mason bee in the upper left tunnel is still at work bringing pollen and laying eggs.

In this photo, taken on 15 May 2015, two tunnels in our bee box are already full of eggs and are sealed with mud. A mason bee in the upper left tunnel is still at work bringing pollen and laying eggs.


Honeybees are on the rise but pollinator demand grows faster

Recent research shows that while populations of Honeybees are on the rise, the overall need for pollinators is rising faster. Good reasons to create pollinator habitat for our many native bees and pollinating insects near crops!

From Cell Press: The notion that a decline in pollinators may threaten the human food supply – producing a situation that has been referred to as a “pollination crisis” – can be considered a myth, at least where honey bees are concerned, say researchers reporting online on May 7th in Current Biology, a Cell Press publication. First of all, most agricultural crop production does not depend on pollinators. On top of that, while honey bees may be dwindling in some parts of the world, the number of domesticated bees world-wide is actually on the rise, their new report shows.

“The honey bee decline observed in the USA and in other European countries including Great Britain, which has been attributed in part to parasitic mites and more recently to colony collapse disorder, could be misguiding us to think that this is a global phenomenon,” said Marcelo Aizen of Universidad Nacional del Comahue in Argentina. “We found here that is not the case.”

By analyzing data from the Food and Agriculture Organization of the United Nations for temporal trends in the number of commercial bee hives, they found that the global stock of domesticated honey bees has increased by about 45 percent over the last five decades. That increase has primarily been driven by an increased demand for honey from a growing human population, rather than an increased need for pollinators, he added.

But the news isn’t all good: The data also show that the demand for crops that rely on insects for pollination has more than tripled over the last half century, suggesting that the global capacity for pollination may still be under considerable stress. These crops include “luxury” agriculture items, now common in any supermarket, like plums, raspberries, and cherries, as well as mangos, guavas, Brazil nuts, and cashew nuts.

“We were particularly astonished when we found that the fraction of agricultural production that depends on pollinators, which includes all of these luxury agriculture items, started growing at a faster pace since the fall of communism in the former USSR and Eastern Europe, and at a much higher rate than the larger fraction of agricultural production that does not depend on pollinators, including wheat and rice, which just follow human population growth,” Aizen said. “Although the primary cause of the accelerating increase of pollinator-dependent crops seems to be economic and political – not biological – their rapid expansion has the potential to trigger future pollination problems for both these crops and native species in neighboring areas.”

The associated increase in demand for agricultural land could also hasten the destruction of habitat that now supports hundreds or thousands of species of wild pollinators, which would in turn cause a drop in crop yield, he said.

“Most importantly, decreasing yield by these pollinator-dependent crops surely would imply rising market prices, which undoubtedly would constitute a further incentive for their cultivation,” Aizen said. “This situation would create a positive feedback circuit that could promote more habitat destruction and further deterioration of pollination services. The good news is that less-intensively managed agro-ecosystems that preserve patches of natural and semi-natural habitats and uncultivated field edges can sustain abundant and diverse communities of wild pollinators.”

 The researchers include Marcelo A. Aizen, Universidad Nacional del Comahue, Rio Negro, Argentina; and Lawrence D. Harder, of University of Calgary, Calgary, Alberta, Canada.

Contact: Cathleen Genova
Cell Press

Growing common milkweed from seed – easy steps for beginners

Text and photos by L Heroux │FWG Volunteer

The monarch migration is truly one of the world’s greatest natural wonders, yet it is threatened by habitat loss. . . The need for host plants for larvae and energy sources for adults applies to all monarch and butterfly populations around the world. — MonarchWatch (

Common milkweed | Asclepias syriaca by C. Hanrahan

If you’ve never grown anything from seed, growing milkweed is a great way to start. You will develop skills applicable to starting other types of plants, and you could become part of a cross-continental chain of waystations dedicated to sustaining the entire lifecycle of monarch butterflies. The FWG is a registered Monarch Waystation. Your garden could be too! Continue reading

Urban Beekeepers Keep Cities Abuzz with Pollinators

By Katherine Harmon  | Scientific American March 31, 2009

Paris, San Francisco, Toronto, Chicago. These cosmopolitan cities hardly conjure up the bucolic image of an ideal home for honeybees. But to millions of busy bees, they’re just that. Whereas large-scale commercial beekeepers are busy trucking hives from state to state to pollinate crops, city-dwellers are learning a thing or two about home-raised honey. Bees are being cultivated on roofs everywhere from the Paris Opera House to Chicago’s City Hall.

Like the honeybee itself, urban beekeepers are a “small but mighty” group, says fourth-generation beekeeper Andrew Coté, founder of the New York City Beekeepers Association. With so much buzz about colony collapse disorder (CCD), even those who live far from the farms and orchards are pitching in to beef up the nation’s bee populations (while reaping some sweet rewards for themselves).

Read the full article here.