Get to Know Wild Bee Hotels
Get to Know Wild Bee Hotels
By Crown Bees
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| A truly healthy wild bee hotel set up |
Tips for 5-Star Wild Bee Hotels
Bee hotels
are fast becoming a backyard staple. Similar to birdhouses, bee hotels provide
vital and missing nesting habitat. In the wild, hole-nesting bees usually nest
in holes in standing dead trees, fallen logs, and broken branches of bushes and
large grasses. Wild hole-nesting bees are desperately searching for suitable
nesting sites and we’ve seen them make do by nesting in the ends of old garden
hose nozzles, openings in metal garden furniture, and even the hollow ends of
wind chimes. But unlike birdhouses, we can’t just build bee hotels and leave
them alone. Bee hotels need to be maintained and managed or they are destined
to become slums for bees. Our bee guests deserve the best accommodations!
Opening our Eyes to the Real World
of Bees
The bees
that nest in bee hotels are really, really different than honey bees or
bumblebees. We’ve all grown up learning about the social structure of honey and
bumblebees and we’ve come to think that their lifestyle represents all bee
behavior. The truth is, the world is home to 21,000 species of bees (and more
are discovered every year) and a whopping 90% of bee species do not live in
social structures.
Instead,
most of the world’s bees live alone. We call this bee behavior and lifestyle “solitary” and every solitary bee
is fertile. Solitary female bees are fertile queens and they have all the duty
and responsibility to take care of their young. Each female bee has to gather
pollen and nectar, build nests, and lay eggs.
Solitary
female bees are gentle because they are too busy to aggressively protect their
nesting site and they simply can’t risk their lives. Solitary bees will only
defend themselves as a last resort, like when they are accidentally squished or
stepped on. Many solitary bees have barbless stingers and rarely does someone
develop an anaphylactic allergic reaction to their mild venom.
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| About 1,000 hole-nesting bee species are native to North America |
Solitary
bees don’t live in colonies, they don’t build hives, they don’t make honey or
wax, and they don’t form attack swarms. To understand the world’s bees, we kind
of, sort of, have to forget everything we think we know about bees. Out of the
world’s 21,000 + bee species, there are only 7 species of honey bees after all,
and bees are as diverse as apples to oranges and pears.
To Build a Great Bee Hotel, Get to
Know Wild Hole-Nesting Bees
So, if 90%
of bees don’t live in hives, how do they live? About 70% of bees species nest
underground and the remaining 30% nest in cavities or holes in wood or hollow
broken stems. Some hole-nesting bees like to drill their own holes and these
are called carpenter bees. Large carpenter bees, in the Xylocopa genus, chew tunnels
in solid wood and since it takes so much time to dig a good tunnel they reuse
nesting homes. Small carpenter bees, in the Ceratina genus, prefer to chew
tunnels in the soft pith of broken stems like in raspberry and blackberry
canes.
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| Blue orchard mason bees are gentle, easy to raise spring pollinators |
Many
hole-nesting bees are too small (and too efficient!) to chew their own holes in
solid wood. Instead, they save time and energy by nesting in pre-made holes
like old grub tunnels. Or they use the crevice in peeling bark and build just
one wall along the bottom. Hole-nesting bees that nest in pre-made cavities
come in a variety of sizes and it’s best for them to nest in a hole that is
just the right size and depth for them. Examples of popular hole-nesting garden
pollinators are blue orchard mason bees (Osmia
lignaria) and alfalfa leafcutter bees (Megachile
rotundata).
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| Peak-a-boo: a mason bee inside of a cardboard tube |
Most
solitary bees have a short lifespan as flying adults. For example, male mason
bees are only flying for 2 weeks, long enough to mate, and female mason bees
are actively flying for 4-6 weeks. With such a short timeframe as adults,
solitary bees do not make honey. This short lifespan also drives some solitary
bees to have a short flying range from home, too. When they first look for a
good nesting spot they may fly a few miles searching, but once they check into
their new bee home they only fly a few hundred feet (about 100 meters) from
their nesting site. Surprisingly, a big chunk of a solitary bee’s life is spent
in their nesting site hibernating over the winter.
What’s Inside a Hole-nesting Bee’s
Nest?
The female
bee is building nesting chambers inside the nesting hole and she builds them in
a series, all in a line. Of course, she starts at the back and each nesting
chamber is provisioned with food for one egg, which is a mix of pollen and
nectar called a pollen loaf. The female bee lays an egg that is firmly placed
in the pollen loaf and then seals the chamber with a protective material to
keep each egg safe as the next chamber is built. The protective material is
either a wall between nesting chambers or it is a protective cocoon that the
mother builds to encase the larva as it develops.
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| Mud walls, pollen loaves, and larvae inside a mason bee nest |
The
protective nesting material depends on the species and when that species is
active in the year. Many mason bees are active in early spring and they use
mud, which is wet and workable for gathering. Some spring mason bees use chewed
up leaf bits (called leaf mastic) or a mix of pebbles, mud, and leaves. Leafcutter
bees build protective leafy cocoons from the summer’s abundance of soft,
pliable leaves. Resin bees gather sap while it is warm and flowing in the hot
summer months. Some bee species mix a few ingredients together and all bees
protect their nesting hole with an extra thick layer of nesting material. This
protective layer is right at the edge of the hole and it’s called a capped end.
The materials used for capped ends and their texture gives us a clue to who
built the nest.
After the
bee egg is laid, it can either hatch and develop into a flying adult right away
or go into hibernation, otherwise known as diapause. Bee larvae are usually
white and they look like chubby grubs. Once the larvae eats its pollen loaf and
has nothing left to eat it spins a cocoon and goes through the cycles of
metamorphosis. Spring mason bee eggs hatch and develop over the summer and they
hibernate as fully formed adult bees, which makes them ready to go as soon as
the daytime spring weather warms above 55*F consistently.
We can easily
and safely harvest blue orchard mason bee cocoons in the fall and take care of
their sturdy, waterproof cocoons by storing them in the fridge. We’re learning
more about how other wild bees develop in their cocoons so that we know when we
can safely and easily harvest cocoons to ensure the bee’s health.
Many
hole-nesting bees that are active in the summer need warm weather to incubate
to finish developing. Some bee species are able to have more than one
generation develop in the long summer season. For example, alfalfa leafcutter
bees can hatch and develop right away and new adults are called second
generation bees. This means that the leafcutter bees can spend even more time
pollinating your garden and farm.
Pests and Diseases that Harm Bee
Hotels
There are
a lot of tutorials for bee hotels and their intentions are great,
but one big piece of knowledge missing about hole-nesting bees is the fact that
they struggle with pests, diseases, and predators just like any other creature.
Man-made nesting holes are not the same as the nesting holes found in nature
and the nesting holes of bee hotels are close enough together for common diseases and pests to spread and overrun a bee hotel.
To reduce and deter diseases and pests is easy, simply harvest cocoons and
separate healthy cocoons from infected nesting chambers.
The three
big problems that hole-nesting bees face are pollen mites (they eat the pollen
and nectar loaf before the bee larva does), chalkbrood (a fungal infection that
converts a larva into a mass of fungal spores), and parasitic wasps (gnat-sized
wasps that lay eggs inside of healthy larvae). As you harvest cocoons, you can
learn how to identify infected chambers and keep healthy cocoons safe.There are larger, more well-known predators
like ants, certain beetles and birds.
Provide easy to open nesting holes
and learn about your native bees
Design Tips for Successful Bee
Hotels
As experts
with decades of experience raising hole-nesting bees, the following are tips
for how Crown Bees would design and manage a bee hotel. Some of the tips sound
time-consuming, but in reality each step should only take a few moments. Our
effort to do things right is well worth it since the UN has reported that 40%
of the world’s insect pollinators are facing extinction. Our bee hotel’s wild
hole-nesting bee residents are the bees that actually need our help.
1. Protect developing larvae. Plan your bee hotel ahead of time so
that you can remove nesting materials as they are filled and store the filled
nesting holes in a warm location. You want to keep nesting materials in
locations that have similar temperatures as the outdoors, like a garden shed or
unheated garage. Removing and protecting filled nesting holes in a fine mesh
bag keeps the small parasitic wasps from being able to attack larvae. To
protect a drilled block of wood, place liner inserts or rolled paper inserts
(pinch the back end closed) into each drilled hole and remove and replace these
as they are filled.
Keep an
eye on the filled nesting materials. Parasitic wasps may have already attacked
and they are able to develop into adults very quickly, you don’t want them to
harm more larvae. Also watch to see if your bees are the type that develop in
the same season they were laid and are ready to emerge.
2. Provide nesting holes in the proper size range, made of the right
materials. Avoid bamboo and plastic straws, as these do not let the moist
pollen loaf breathe. Many bamboo shoots are much too large for any North
American bee to use. Nesting holes should be between 4-10 mm in size and should
be about 6” long. Nesting holes that are too shallow will skew the sex range of
next generation’s bees. Natural, locally available nesting materials are best.
Crown Bees’ Pollinator Pack provides cardboard tubes and lake
reeds in the right size range and they are easy to open for cocoon harvest.
3. Protect nesting materials from
wind, rain, and birds.
Build a protective outer structure that has a 2-3” overhang. If birds are
attacking the nesting holes, use 1” wide wire cloth and bubble around the bee
hotel. Do not install wire cloth flush against the nesting holes because this
will obstruct the bees from entering. Bees need some landing space for approaching
and taking off.
4. Avoid a hotel that is too large. While a bee hotel that is 4 feet
wide and 6 feet tall looks great, draws a lot of attention and raises awareness
to our bees, this size is much too ambitious and will become a burden to
maintain. Provide a bee hotel that matches what the area nearby the house can
provide, for example, many flowering trees and bushes can provide more pollen
than a meadow of flowers can. Also, think about the time that you can devote to
cleaning and managing the bees that move in.
5. Location and a word about
solitary predatory wasps.
Orient the bee hotel to face the morning sun, as hole-nesting bees are
cold-blooded and need the sun’s warmth to get the energy needed to fly. We know
that mason bees prefer some afternoon shade and have heard that too much shade
could actually attract solitary hole-nesting wasps. Solitary wasps are
predators of garden pests and they fill nesting holes with caterpillars,
aphids, and even spiders. Hole-nesting wasps are great beneficial insects that
are a good indicator that your garden is balanced and supports all insects.
Solitary wasp larvae are also white but their shape and skin are different from
a bee, they are longer with large bumps and they feel waxy.
You might
want to provide two bee hotels in your yard with each bee hotel facing a
different direction. One house can face east and another can face southeast. We
are curious to learn if bee species have a preference for orientation of their
nesting house. You might also want to place a hotel in your yard and one in a
wild location, like a meadow or forest. A natural habitat could be home to a
different mix of local wild bees that you could then introduce to your yard.
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| To ensure your wild bee’s health, harvest their cocoons |
6. Harvest cocoons. After protecting and storing
filled nesting materials over the winter, open materials and harvest
cocoons in the
early spring. If you can, organize and separate cocoons based on appearance and
when their nesting holes were capped. When you incubate in the BeeGuardian bag you have more control for
releasing the bees outside. Incubating inside of the fine mesh bag also helps you
reduce the release of the gnat-sized parasitic wasps.
Join the Native Bee Network
You can
help us all learn more about our native hole-nesting bees by participating in
Crown Bee’s citizen science project. The Native
Bee Network is a
way for gardeners and farmers to gather information and share it with other
growers. Traditional scientific knowledge can tell us a bee’s scientific name
but there is so much more we can know about each bee species. We need to know
what size hole they prefer, what nesting materials they use, if they are
specialists or generalists, and when they are active. The answers to these
questions can be answered by anyone that takes the time to watch the bee guests
and protect their nesting materials.
Join the Native Bee Network to
learn and share knowledge with gardeners and farmers.
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