America’s Bee Crisis: Part 6 – Oh, Give Them a Home

This is the final installment in my series about the state of bees in America. Prior posts are:
Part 1 – How Did We Get Here?
Part 2 – Our Big, BEE-utiful World
Part 3 – Native Bees Get It Done!
Part 4 – BEE Part of the Solution
Part 5 – Paradise Found


“Bees do have a smell, you know, and if they don’t they should, for their feet are dusted with the spice of a million flowers.”
~Ray Bradbury, Dandelion Wine

The native bees of America are a precious resource, one we should do everything in our power to protect. To protect them we must understand them, and to understand them we must observe them. Turning your yard and garden into a pollinator paradise will give you ample opportunity to observe a wide variety of native bees as they gather pollen and nectar. Providing nesting materials will give you the pleasure of watching them build and provision nests for their young. Cavity nesting bees are the easiest to coax into using a manmade structure, and of these, the mason bee is the most commonly kept by home gardeners. Watching these industrious, gentle little bees is a true delight! Keeping them is so easy, I hope many of you will consider giving it a try this spring. Read on to find out how.

America’s Bee Crisis: Part 6 – Oh, Give Them a Home

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Blue Orchard Mason Bees

Mason bees are active in spring, which makes them the perfect pollinators for fruiting trees and shrubs, such as apple, cherry, plum, blueberry, and more! When daytime temperatures average 55°F the males emerge from hibernation, feed on nectar, and hang out at the nest site waiting for females. A few days later the females emerge to join them, and are immediately mated with. The males, having fulfilled their life’s purpose by mating, now die. The females get right to work, seeking out an appropriate nest site and provisioning it for their young. Once a female mason bee has found a suitable hole for nesting in she walks up and down the length of it a few times, clearing debris and marking it with her own unique pheromones so other bees will know it’s taken.

If necessary, she will collect mud to seal the back of the nesting chamber, then she begins gathering food. On each flight she will visit numerous flowers, packing pollen tightly into the scopae (coarse hairs) on her abdomen, and drinking nectar to fill her honey-stomach. She then returns to her nest and enters head first. When she reaches the egg chamber she regurgitates the nectar and then exits and turns around, backing in this time. Now she uses her hind legs to scrape all of the pollen out of her scopae. Again, she must exit and turn around. Now she comes back and uses her mandibles (jaws) to mix the nectar and pollen together into a sticky mass. She will repeat this process again and again until she has a sticky pollen ball almost as large as herself. At night and on very rainy days she will rest in the nesting chamber.

Pollen lumps with mason bee eggs.

Pollen lumps with mason bee eggs.

Once she has gathered enough food, the mason bee backs in one more time and lays a single egg on the pollen ball. If she chooses to fertilize the egg, it will be a female. If she lays an unfertilized egg, it will be a male. The female eggs are always positioned at the rear of the nest holes, where they will be safe from predators. The males are laid closer to the front, since they are the first to emerge. Now the mason bee must collect mud to seal the egg chamber. She uses her powerful jaws to roll mud into a ball and carries it back to the nest. She packs the mud around the outer edges of the egg chamber, gradually working toward the center. It takes her many trips to collect enough mud. Once this solid partition is complete she can begin anew, gathering pollen and nectar for another egg. Working this way the mason bee will create a succession of nest cells, each separated by a mud wall, each containing a pollen ball and a single egg. When she gets to the end she builds one final mud wall at the entrance of the nest chamber. This last mud plug is very thick to deter predators.

Now the mason bee must search for another suitable nest site to begin the process again. She will continue creating nest cells, provisioning them with food, and laying eggs until she dies. If she does not succumb to bad weather or get eaten by a predator, the mason bee may be active for about a month, working ceaselessly until her death. But snug in their nest cells the next generation of mason bees are beginning their lives. The eggs have hatched and the larvae are busy eating the pollen. For several weeks they do nothing but eat and grow. When a larva has consumed all the pollen it spins a cocoon and becomes a pupa. The pupa undergoes a metamorphosis: its skin hardens into an exoskeleton and the organs rearrange themselves. In a few more weeks it is a new adult bee. By this time summer is fading. The new mason bee will stay safe inside its cocoon during the winter, sustaining itself on its fat reserves. When daytime temperatures average 55°F the following spring, these new bees emerge to start the lifecycle again.

Mason bee emerging from cocoon in spring.

Mason bee emerging from cocoon in spring.

Nesting Requirements
Mason bees will use for their nest any hole which is roughly 5/16” (7mm) in diameter. Anywhere they can find a hole this size they will nest in it: hollow reeds, the space between wood shingles on houses, snail shells, in electrical outlets, keyholes in doors, or screw holes in wooden decks and furniture. If there’s a hole about the width of a pencil eraser out there, a mason bee is going to lay an egg in it! However, what a mason bee will use and what will have the highest success rate are not the same thing. To get the optimum ratio of males to females the hole should be about 6 inches deep. Mason bees will nest in any kind of material, but wood or paper seem to be their preference. Some people have coaxed mason bees to nest in bundles of plastic drinking straws, but I strongly discourage this as mold is a serious issue.

Mason bee searching for vacant nesting cavity.

Mason bee searching for vacant nesting cavity.

Selecting a Mason Bee House
Nest blocks are a common choice, being the least expensive and the easiest to make at home. The premise is simple: purchase a chunk of untreated, non-aromatic wood (i.e. not cedar or pine) that is 4 inches wide by 6 inches deep and cut it to any length you want. Attach a 5/16” drill bit to an electric drill and drill as many holes as you can to a depth of about 5½”. Hang this on your house and watch the mason bees go to town. Unfortunately it’s not possible to extract the cocoons from a nest block. If you choose to use one of these you will need to purchase paper straws to line the nest cavities. The straws are not reusable.

Mason bees nesting in drilled wood, by Jenny Mackness.

Mason bees nesting in drilled wood, by Jenny Mackness.

Natural reeds are perhaps the most visually attractive option. One may gather up (or purchase) several hollow reeds (such as bamboo) into a bundle and hang them up. Bundles of natural reeds are quite pretty, and mason bees love them and will happily make their nests in them. The tricky part is figuring out how to get the cocoons out. Some reeds are very hard and can be difficult to cut open without damaging the cocoons inside. The paper straw inserts may work for these, but probably not as well since reeds are not uniform in size.

Mason bees nesting in natural reeds, by poppet with a camera.

Mason bees nesting in natural reeds, by poppet with a camera.

Cardboard tubes are a popular option of late. These specially made cardboard tubes are closed off at one end are bundled together in a wooden or metal “bee house”. The tubes require paper straws, unless they are an easy-tear variety. Cardboard tubes are easy to use and a fairly inexpensive option for someone just starting out who isn’t sure about their level of commitment.

Stacking Trays are the best and most cost-effective option for long-term use. If you feel certain that you’re just going to love keeping mason bees, or if you’ve tried one of the methods above and want to “graduate” to something more permanent, then this is the way to go. For stacking trays, 5/16” diameter grooves are routed out of boards to form a nesting chamber. The boards are then stacked on top of each other and the bundle is held together with a plastic cord or tape to form one solid block. This block is placed inside a protective “bee house”. At the end of the season the boards are separated and the cocoons will fall out or can be gently pried loose. The boards can be scrubbed and restacked for the following season, and they can be used again and again.

Mason bee house with stacking trays.

Mason bee house with stacking trays.

I have had great success with stacking tray systems and in a good year may see a tenfold increase in my bees! These are so much easier to harvest the cocoons from and clean than any of the other options above. The only drawback is that they’re difficult to make on your own and cost a bit more to purchase than the others. But I feel they really pay for themselves in the long-run since they can be used continually without buying replacement parts, and because the bees are healthier and more prolific with these systems.

Good Mason Bee Stewardship
The most important factor to consider when choosing a mason bee house is the ability to get the cocoons out of the house. In the wild a mason bee may lay a couple eggs here, a few there, and a few more much farther away. They don’t often have the opportunity to pile themselves into the kind of close quarters they find in a bee house. Like all living things, they are vulnerable to parasites and disease. When you house many of them together these things can easily spread. So it is imperative when keeping mason bees that you have a way to remove the cocoons from the nesting material and inspect them for diseased or parasitized specimens.

Harvesting mason bee cocoons from tray.

Harvesting mason bee cocoons from tray.

Removal of the cocoons happens in the late fall, after the mason bees have developed into adults and are hibernating for the winter. Their cocoons are quite sturdy and the bees do not seem to mind (or even notice) being handled. All the cocoons should be removed from the nests and inspected for parasites or disease. Suspect cocoons should be discarded and the rest can be kept in a ventilated container (such as a jar or yogurt tub with holes punched in the lid) in a cold place, like your garage or a garden shed. (A refrigerator is not a good place to store the cocoons as it will dry them out, killing the bees.) The following spring you put them back out with your bee houses.

Siting Your Mason Bee House
Bees rely on the warmth of the sun to raise their body temperature, enabling them to fly. Your mason bee house should be hung facing east or south so your bees can get to work early in the morning. Hanging it on the side of a house or other building will give your bees protection from wind and rain. Hang the house high enough up that it will not be splattered by mud, but not so high that you can’t see it. Mason bees are very gentle and will not sting you! I often stand right in front of my bee houses with a kid on my shoulders and watch them fly in and out.

Food & Mud
In order to successfully raise mason bees, you must have flowers and mud available to them for the entirety of their nest-building period. Be sure that either you or your near neighbors has a succession of flowering plants available from early to late spring. You can provide mason bees with the mud they need by digging up a little area of your yard or garden near the nest site and keeping the earth moistened for the bees to use.

Mason bee nest with mud partitions, by sighmanb.

Mason bee nest with mud partitions, by sighmanb.

Purchasing Mason Bee Cocoons
If you live in a neighborhood with plenty of bee habitat, then there’s a good chance that you can just hang up a mason bee house and watch them move in. But if mason bees fail to show up you can purchase cocoons. Local garden centers often sell mason bee cocoons that are appropriate for your area. You can also purchase cocoons online. However, there are different mason bee species that are specific to the different regions of the U.S. and it is imperative that you purchase only those bees that are native to your region. Be sure to do your due diligence to find out where the cocoons came from. You don’t want to be responsible for introducing a non-native species. 😉

After several years of mason beekeeping, I’ve recently upgraded my bee houses to 2 large wooden tray stacking systems from Crown Bees and am very pleased with their performance. Tune in next week to learn more about Crown Bees’ products and a chance to win a complete mason bee house kit of your own. 🙂

 

The Nitty Gritty
Since acquiring my mason bees in 2008 I have developed a passionate interest in bees in general, and solitary bees in particular. This series is a culmination of my last 6 years spent reading books, scientific studies, and news articles, as well as observing bees in the wild. For further reading on this topic, I suggest:

To learn more about mason bees: The Orchard Mason Bee, by Brian L. Griffin, and Pollination with Mason Bees, by Margriet Dogterom.

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