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Leaf-Cutter Bees
Order Hymenoptera, family Megachilidae
(part)
Copyright © 1996 by
Louise Kulzer
This article originally appeared in Scarabogram,
August 1996, New Series No. 196, p. 3.
I always like late spring and summer, because as
soon as my roses start looking good, I can be
pretty sure the leaf-cutter bees are not far behind.
Leaf-cutter bees are solitary bees in the family
Megachilidae (but remember, not all megachilids
cut leaves). Those that do cut leaves use them to
line their nests, which are constructed in a variety
of places, such as tunnels in the ground, under
stones, in the pith of brambles (Frost 1959) or
excavated in wood.
Two species of Megachile
(from Howard 1903)
[Most megachilids use pre-existing holes and do not dig their own burrows. Of 20
genera in the Pacific Northwest, three (Trachusa, most Megachile, some Hoplitis) use
leaf pieces and many Osmia (a large genus also including the mason bees) use chewedup leaf (Stephen et al. 1969).]
Actually, it's a bit more elaborate
than just lining the nest burrow.
Leaf-cutter bees construct several
cells from the leaf pieces they
collect. The cells are positioned end
to end in a long burrow. Several
circular leaf pieces form the bottom,
then oblong pieces are placed along
the sides to form a "thimble." This
thimble is then provisioned with
nectar and pollen, and an egg is laid
in it. Then the bee cuts more circular
pieces to close the cell. Once the cell
is closed, the bee starts another cell
above the first, until the whole
cavity is filled. Like all solitary bees,
the female leaves the nest after it is
closed. The grubs fend for
themselves on the nectar and pollen.
The adult leaf-cutter bee is smaller than a honey bee, dark, often hairy, with a
prominent pollen basket below. Females are workaholics, and are a delight to watch
because, being so intent on cutting leaves, they usually ignore a nearby observer! The
leaf sections are cut with the mandibles, and the bee forms an arc with her head along
the leaf edge to make the circular shape. (They remind me a little of an electric can
opener, only with much more personality.)
Leaf-cutter bees are most notorious for
cutting circular and oval holes in rose
leaves, but I have seen them gather
Hypericum sp. (St. John's wort), and this
year they are particularly attracted to my
vine maple. None of these plants are in the
same family either, so that's not it. I think
they choose plants that have a specific
texture and thickness, much as one might
choose paper of a certain weight for a report
cover. It would be interesting to compare
observations, fellow Scarabs!
Next time you see round or oval holes in
your rose leaves, notice if they are regular
and neat in outline (rather than ragged, like
beetle damage is). If so, don't be dismayed.
Just wait quietly and you may be rewarded
by seeing first-hand the efficient, elegant
work of the leaf-cutter bee.
References
Frost, S.W. 1959. Insect Life and Insect
Natural History. Dover Publications,
NY.
Leaf-cutter bee damage on rose. Note both
oval and circular cuts.
Stephen, W.P., G.E. Bohart, & P.F. Torchio. 1969. The Biology and External
Morphology of Bees, With a Synopsis of the Genera of Northwestern America.
Agricultural Experiment Station, Oregon State University, Corvallis.
Leafcutter Bees no. 5.576
by W.S. Cranshaw 1
Quick Facts...
Leafcutter bees are native bees, important as pollinators. Leafcutter bees are not aggressive
and have a mild sting that is used only when they are handled. Leafcutter bees cut the leaves
of plants. The cut leaf fragments are used to form nest cells. Leafcutter bees nest in soft, rotted
wood or in the stems of large, pithy plants, such as roses.
Leafcutter bees are important native insects of the western United States. They use cut leaf fragments to
construct their nest cells. They often are essential pollinators of wild plants. Some leafcutter bees are even
semidomesticated to help produce alfalfa seed. However, their habit of leaf cutting, as well as their
nesting in soft wood or plant stems, often attracts attention and concern.
Life History and Habits
Most common leafcutter bees (Megachile spp.) are approximately the size of the common honeybee,
although they are somewhat darker with light bands on the abdomen. They also have different habits.
Leafcutter bees are not aggressive and sting only when handled. Their sting is very mild, much less
painful than that of honeybees or yellowjacket wasps.
Leafcutter bees are solitary bees, meaning that they don’t produce colonies as do social insects
(honeybees, yellowjackets, ants, etc.). Instead, individual female leafcutter bees do all the work of
rearing. This includes digging out nesting areas, creating nest cells and providing their young with food.
Adult females may live up to two months and lay some 35 to 40 eggs during this time. Leafcutter bees
nest in soft, rotted wood; thick-stemmed, pithy plants (e.g., rose); and in similar materials that the bees
can easily cut through and excavate. Nest tunnels may extend several inches deep and coarse sawdust
may be deposited at the entrance. This sometimes causes confusion with other wood nesting insects such
as carpenter ants. However, leafcutter bees restrict their tunneling to soft, rotted wood and do not cause
damage to homes or other wooden structures. There also are concerns about leafcutter bee nesting in rose
canes, excavating the pith of pruned canes. Leafcutter bees sometimes nest in the largest diameter rose
canes but cause little damage because they restrict tunneling to the pith and rarely girdle cambium.
Furthermore, other insects, including various hunting wasps (Pemphredon species) and small carpenter
bees more commonly tunnel and nest in rose canes.
After the nest is made, the bees collect fragments of leaves to construct individual nest cells. The bees cut
leaves in a distinctive manner, making a smooth semicircular cut about 3/4 inch in diameter from the edge
of leaves. Although they cut many types of leaves, leafcutter bees prefer certain types, notably rose, green
ash, lilac and Virginia creeper. This injury often is only a minor curiosity. However, where leafcutter bees
are abundant and concentrate on cultivated plantings, the removal of leaf tissues can be damaging.
Serious damage most often occurs in isolated rural plantings. Leafcutter bees do not eat the cut pieces of
leaves that they remove. Instead, they carry them back to the nest and use them to fashion nest cells
within the previously constructed tunnels. Then they provision each leaf-lined cell with a mixture of
nectar and pollen. The female lays an egg and seals the cell, producing a finished nest cell that somewhat
resembles a cigar butt. A series of closely packed cells are produced in sequence. A finished nest tunnel
may contain a dozen or more cells forming a tube 4 to 8 inches long. The young bees develop and remain
within the cells, emerging the next season.
There are a great many parasites that act as important natural enemies of leafcutter bees. As a result, leaf
cutting activity may vary widely from year to year. Parasitic bees and wasps, velvet ants and certain
blister beetles are among the most important enemies of leafcutter bees and other solitary bees.
At least one species of leafcutter bee is cultivated for agricultural use in Colorado. Megachile rotundata is
used to pollinate alfalfa grown for seed, a function that it does far more efficiently than honeybees. These
leafcutter bees are provided with predrilled “bee boards” that they use for nest construction. At the end of
the season, the nest cells with developing bees are collected and carefully stored, to be released the
subsequent season when alfalfa blooms.
Control
Insecticides are ineffective for preventing leaf cutting. The only known control of leaf injuries is to cover
susceptible plants with cheesecloth or other loose netting during periods when leafcutter bees are
most active. Numbers of leafcutter bees in an area can be reduced if breeding sites are eliminated,
although these might be diffi cult to detect. Look for rotting boards with sawdust pushed out of excavated
tunnels or thick stemmed plants with hollowed openings. To prevent leafcutter bees from tunneling into
rose canes, seal exposed pith as canes are pruned. This can be easily achieved by placing a thumb tack, bit
of sealing wax or white glue on the opening.
Colorado State University Extension
entomologist and professor, bioagricultural
sciences and pest management.
1
Orchard Mason Bees
This page offers WWW links outside WSU as an option for finding further information. No endorsement of
product or information is implied by including this link.
The orchard mason bee (Osmia lignaria) is a gentle beneficial insect that has potential as a pollinator of apples,
cherries, and other tree fruits. It is found throughout most of North America, particularly in wooded areas but
often around homes in towns and cities.
Homeowners sometimes become concerned when they see the bee entering cavities under shake siding or
investigating nail holes or other cavities in wood during March through early June. These are not destructive
insects, since they do not excavate holes in the wood, though they will clean out loose debris. No controls are
recommended, since no damage is done. To prevent the bee from nesting, holes may be filled with caulking.
The orchard mason bee is usually slightly smaller than a honey bee and a shiny dark blue in color. The actual
size of the bee depends largely upon the size of the hole in which it grew. Males (Fig. 1) are smaller than
females, have longer antennae and an additional tuft of light colored hairs on the face. Females (Fig. 2) have
hairs on the underside of the abdomen, called the "scopa", adapted for carrying pollen.
Fig. 1 Male orchard bee. Note the long antennae. (The red coloring is caused by Chaetodactylus sp. mites
riding on the bee.)
Female orchard mason bee on blossom.
Fig. 2 The female approaches the flower from the top, transferring pollen from other flowers in the process.
Nesting Habits
The female uses existing holes in wood for a nest. She chooses holes slightly larger than her body, usually 1/4
to 3/8 inches in diameter. The bee first places a mud plug at the bottom of the hole, then brings in 15 to 20
loads of nectar and pollen which she collects from spring flowers, including apples and other fruits. If you
watch the bee closely as she enters the nest, you can see the pollen on the underside of her abdomen.
When the female has provided a sufficient supply of food for the larva, she lays an egg and then seals the cell
with a thin mud plug. She then provisions another cell, and continues in this fashion until the hole is nearly
full. Finally the bee plasters a thick mud plug at the entrance (Fig. 3). Some wasps and leaf-cutter bees also
build nests in such holes but their nests can be distinguished from the orchard mason bee nests by
characteristics of the plug. The plug of the mason bee is always rough while the wasp prepares a smooth
plug.(Fig. 4). Leaf-cutters seal the holes with chewed-up leaves.
Fig. 3 Orchard mason bee putting entrance plug in her nest.
Fig. 4 Trap nest with holes filled by female bee. Note smooth wasp plugs on the right.
The female orchard mason bee lives for about a month and can produce one or two eggs each day. The larva
hatches from the egg after a few days and begins to eat its provisions. When the pollen-nectar mass is
completely eaten in about 10 days, the larva spins a cocoon and pupates within the cell.
Near the end of the summer the bee transforms to the adult stage but remains in the cocoon throughout the
winter. In the spring, when the weather has warmed up sufficiently, the males begin to emerge by chewing
their way out of the cocoons and through the mud plugs. The females, which are almost always in the inner
cells of the tunnel, emerge several days later. One or two weeks may be required for all the bees to emerge
during cool weather.
Females mate soon after emerging, then begin nesting in 3 to 4 days. The bees forage on a number of different
flowers. In wooded areas, they seem to prefer ballhead waterleaf. In urban areas, dandelion and Oregon grape
are commonly visited, in addition to cherries and apples.
This Bee Is Gentle
The orchard mason bee is non-aggressive and will sting only if handled roughly or if it should get trapped
under clothing. It is less objectionable than the honey bee as a pollinator in urban areas and should be
encouraged. Efforts are being made experimentally to develop large populations of these bees to use as a
supplement to honey bees for fruit pollination, much as the alfalfa leafcutting bee was developed for alfalfa
seed pollination.
Collecting Orchard Mason Bees
If you wish to develop populations for pollinating a home or commercial orchard, you can set out trap nests to
collect the bees. Trap nests can be made by drilling holes 1/4 to 3/8 inches in diameter and 3 to 6 inches deep
in pine or fir 4x4's. A "brad-point bit" leaves a nice, smooth hole. Alfalfa leafcutting bee boards with hole
diameters of at least 1/4 inch can also be used. Attach the boards to a house or other structure where you have
seen the bees. Some protection from rain is desirable. You may also place boards on dead trees or posts in
wooded areas near streams where there is a good supply of mud for nest construction and wild flowers on
which to forage.
Position boards where they will receive morning sunlight. Put the nests up in March before the bees begin
nesting and remove them in early to mid-summer when nesting is completed. If the boards are stored outdoors
over winter (under cover to protect them from rain and snow) the bees will usually emerge in March and April.
They should forage for pollen during the period of cherry and apple bloom and afterwards, if sufficient other
flowers are available to them.
Using the Bee in Orchards
If you wish to develop large populations for orchard pollination, you should store the nests under humid
refrigeration at 35 to 40° F. This will permit control of emergence time and reduce predation and parasitism by
the insect enemies of the bees. Do not place the nests in storage until September or October to assure complete
development of the adults. The following spring, place the boards in the orchards in plywood shelters facing
east to catch the morning sun. To hasten emergence, incubate the boards at room temperature for 24 hours
before placing the bees in the orchard. The boards and some new nesting material should be in place a few
days before apples begin to bloom, or earlier if other fruit bloom such as cherries, is available. Provide 5001000 filled holes per acre. These should contain 750-1000 females, assuming an average of 1 1/2 females per
hole. Males also visit flowers, but they do not live long and are not as effective as pollinators. Competing
flowers such as dandelions should be mowed as soon as the fruit begins to bloom.
If no natural mud source is available near the nesting shelters, dig a shallow hole, line it with plastic, and fill it
with moist soil. A simple drip irrigator can be made from a plastic bucket and a piece of drip irrigation tubing
to keep the soil moist.
Developing large populations of the bees may be a slow process under orchard conditions; the short duration
of bloom does not allow the bees to accomplish maximum reproduction. The orchard mason bee also has a
tendency to fly away rather than using or reusing nests in the near vicinity. However, relatively large
populations have been developed in 2 or 3 years in urban situations. Once established, orchard bees will nest in
containers filled with large-diameter drinking straws or paper tubes folded in half.
Nature Study
In addition to their value as pollinators, orchard mason bees are fascinating insects for nature study.
Observation nests can be fashioned from transparent plastic or glass tubes placed in a box that can be opened
for observation. A film and video, The Orchard Mason Bee, depicting the life history and management of the
orchard mason bee is available for rent from the WSU Media Materials Services, Holland/New Library,
Washington State University, Pullman, WA 99164. Phone 509/335-7664 for loan availability.
Filled Orchard Mason Bee observation nest.
What Are They?
Orchard mason bees are native North American bees. They live all across the United States and Southern
Canada, but are particularly common in the Pacific Northwest, especially in the Puget Sound area and western
Cascade Mountains. They are also called "blue orchard bees" and scientists know them as Osmia lignaria.
They are beautiful insects, about 1/3 inch long and blue black with a metallic sheen. Unfortunately, they are
sometimes mistaken for large flies (look closely - they have 2 pairs of wings and are not interested in
garbage!). The females are somewhat larger than the males and the males have a white hairy face. Like all
bees, mason bees collect flower pollen as a protein source for their young and get their energy from flower
nectar. In shopping for groceries, they carry pollen from flower to flower, achieving pollination.
A number of things set mason bees apart from other bees:
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Solitary: They are solitary. Each female bee builds a nest by herself, lays eggs, seals the nest, and
goes about her business. She receives no help from other bees, so there is no colony or "hive" as
in honey bees or bumble bees.
Live Together: Mason bees are attracted to each other. They like to build their nests in
aggregations.
Safe: As with other solitary bees, mason bees are gentle and shy. They have a stinger (actually it
is an egg guide), but they use it only when they are in serious danger, as when they are
purposely caught in the hand. They do not attack to defend their nest or arouse each other in
alarm.
Specialized Pollinators: Mason bees prefer to forage on flowers in the apple family, including
many varieties of apples, cherries, plums, peaches, and similar "stone fruits". Because they
specialize on these plants, they are exceptionally good pollinators of them. They will forage on
other flowers as well.
Hard Working: Orchard mason bees are adapted to a cool climate and can fly in chilly, even
drizzly weather. Thus, they are often busy pollinating when honey bees remain inside the hive.
Build With Bricks: Like the wisest little pig, orchard mason bees build their nests with bricks
(sort of). Each egg chamber in the nest is sealed with a partition of ordinary mud. The entire
nest is also sealed with a hardened mud capping. This is why they are called "mason" bees.
The above features make orchard mason bees the perfect pollinator for those who have a small number of fruit
trees, but may not want to manage honey bee hives. They are also a fascinating wild creature that can be easily
encouraged to colonize the backyard garden environment, to the benefit of the gardener, orchardist,
homeowner, and nature lover. Mason bees are totally safe, even around children and pets.
Keeping
Female mason bees make their nests in hollow cavities. In nature, these are found in the fissured bark of trees
or in the emergence holes of tree-eating grubs. Mason bees can be attracted to you yard. They may already be
in your neighborhood, especially if you live in the Puget Sound region. To make mason bees a part of your
home life, simply provide them with nest holes and make sure they have plenty of flowers to feed on. The ideal
nest hole is 5/16 to 11/32 inches in diameter and 4 to 8 inches deep. The bees will nest in a wide variety of
such cavities. Straws and holes drilled in boards are commonly used. But to produce happy and healthy bees
and to avoid disease build-up, you should give the bees quality housing.
Problems
Orchard mason bees have problems, just like all creatures. They have certain requirements in nest placement,
preferring a warm, dry situation. They must have adequate flowers to raise their brood. And finally, they are
subject to diseases, parasites, and predators. These include fungal diseases of the developing bees, various
types of mites, which compete with the larval bees for foodor parasitize them, and predatory insects or larger
predatory animals like woodpeckers. The most serious of these problems are the diseases and parasites.
Straw Systems
Bare wood holes are acceptable to mason bees, but over time the become fouled with debris and germs. If not
cleaned, the hole loses its attractiveness as a subsequent nest cavity. Mason bees tend to "go away" from such
nest blocks after the first year or two. Diseases and parasites may build up in unhygenic nest blocks. The best
nest system for orchard bees is a smooth wood hole with a porous insert or liner (straw) which can be replaced
each season.
The concept of straw inserts was developed by USDA scientists in studying mason bees. With a straw system,
the filled nests can be removed in the fall, and replaced with new inserts in the spring. The new bees in the
nests can be safely stored in a cool environment until it is time for them to begin the nesting cycle and
pollinate. Then, simply place the nests near the nest blocks and allow the bees to emerge and re-nest in the new
inserts.
Mason bee
From Wikipedia, the free encyclopedia
Mason bee is a common name for species of bees in the genus Osmia, of the family Megachilidae. They are
named from their habit of making compartments of mud in their nests, which are made in hollow reeds or
holes in wood made by wood boring insects.
Species of the genus include the orchard mason bee, Osmia lignaria, the blueberry bee, O. ribifloris, and the
hornfaced bee, O. cornifrons. The former two are native to the Americas and the latter to Japan, although O.
lignaria and O. cornifrons have been moved from their native ranges for commercial purposes. The Red
mason bee, Osmia rufa, is found across the European continent .
Mason bees are increasingly cultivated to improve pollination for early spring fruit flowers. They are used
sometimes as an alternative, but more often as an augmentation for European honey bees.
Unlike honey bees (Apis), they are solitary; every female is fertile and makes her own nest, and there are no
worker bees for these species. Solitary bees produce neither honey nor beeswax. They are immune from
acarine and Varroa mites, but have their own unique parasites, pests and diseases.
Most mason bees live in holes and can be attracted by drilling short holes in a block of wood. They are
excellent spring season pollinators and, since they have no honey to defend, will only sting if squeezed or
stepped on. As such, they make excellent garden "pets", since they both pollinate the plants and are safe for
children and pets.
Osmia species are usually metallic green or blue, though many are blackish. Most have black ventral scopae
which are difficult to notice unless laden with pollen. They have arolia between their claws unlike Megachile
or Anthidium species. The number of Osmia species in North America is probably third in line after Andrena
and Perdita.
Contents
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1 Life Cycle
2 See also
3 External links
4 Further reading
[edit] Life Cycle
Home made nest block showing full occupation
Mason bee nest cell with egg on pollen bed.
Mason bee nest cell with cocoon.
Hornfaced bee Osmia cornifrons
The bees emerge from their cocoons in the spring, with males the first to come out. They remain near the nests
waiting for the females. When the females emerge, the first thing they do is mate. The males die and the
females begin provisioning their nests.
Osmia females like to nest in narrow holes or tubes, typically naturally occurring tubular cavities. Most
commonly this means hollow twigs, but sometimes other similar spaces are used, including empty snail shells
(they do not excavate their own burrows, unlike many bees). A female might inspect several potential nests
before settling in.
Females then visit flowers to gather pollen and nectar, and it will take many trips to complete a pollen/nectar
provision mass. Once a provision mass is complete, the bee backs into the hole and lays an egg on top of the
mass. Then she creates a partition of "mud", which doubles as the back of the next cell. The process continues
until she has filled the cavity. Female-destined eggs are laid in the back of the nest, and male eggs towards the
front.
Once a bee has finished with a nest, she plugs the entrance to the tube, and then may seek out another nest
location.
By the summer, the larva has consumed all of its provisions and begins spinning a cocoon around itself and
enters the pupal stage, and the adult matures either in the fall or winter, hibernating inside its insulatory
cocoon. Most Osmia species are found in places where the temperature drops below 0°C for long durations,
like Canada, and they are well-adapted to cold winters.
CARPENTER BEES
by Mike Potter, Extension Entomologist
University of Kentucky College of Agriculture
In the late-spring and early summer, homeowners often
notice large, black bees hovering around the outside of
their homes. These are probably carpenter bees searching
for mates and favorable sites to construct their nests. Male
carpenter bees are quite aggressive, often hovering in front
of people who are around the nests. The males are quite
harmless, however, since they lack stingers. Female
carpenter bees can inflict a painful sting but seldom will
unless they are handled or molested.
Carpenter bees resemble bumble bees, but the upper surface of their abdomen is bare
and shiny black; bumble bees have a hairy abdomen with at least some yellow
markings.
Despite their similar appearance, the nesting habits of the two types of bees are quite
different. Bumble bees usually nest in the ground whereas carpenter bees tunnel into
wood to lay their eggs. Bare, unpainted or weathered softwoods are preferred,
especially redwood, cedar, cypress and pine. Painted or pressure-treated wood is much
less susceptible to attack. Common nesting sites include eaves, window trim, facia
boards, siding, wooden shakes, decks and outdoor furniture.
Entrance holes are perfectly round.
Nest tunnels are shown
Carpenter bees overwinter as adults in wood within abandoned nest tunnels. They
emerge in the spring, usually in April or May. After mating, the fertilized females
excavate tunnels in wood and lay their eggs within a series of small cells. The cells are
provisioned with a ball of pollen on which the larvae feed, emerging as adults in late
summer. The entrance hole and tunnels are perfectly round and about the diameter of
your finger. Coarse sawdust the color of fresh cut wood will often be present beneath
the entry hole, and burrowing sounds may be heard from within the wood. Female
carpenter bees may excavate new tunnels for egglaying, or enlarge and reuse old ones.
The extent of damage to wood which has been utilized for nesting year after year may
be considerable.
Control
Carpenter bees prefer to attack wood which is bare, weathered and unpainted.
Therefore, the best way to deter the bees is to paint all exposed wood surfaces,
especially those which have a history of being attacked. Wood stains and preservatives
are less reliable than painting, but will provide some degree of repellancy versus bare
wood. To further discourage nesting, garages and outbuildings should be kept closed
when carpenter bees are actively searching for nesting sites.
Liquid sprays of carbaryl (Sevin), chlorpyrifos (Dursban), or a synthetic pyrethroid (e.g.,
permethrin or cyfluthrin) can be applied as a preventive to wood surfaces which are
attracting bees. Residual effectiveness of these insecticides is often only 1-2 weeks,
however, and the treatment may need to be repeated. Tunnels which have already
been excavated are best treated by puffing an insecticidal dust (e.g., 5 percent carbaryl)
into the nest opening. Aerosol sprays labeled for wasp or bee control also are effective.
Leave the hole open for a few days after treatment to allow the bees to contact and
distribute the insecticide throughout the nest galleries. Then plug the entrance hole with
a piece of wooden dowel coated with carpenter's glue, or wood putty. This will protect
against future utilization of the old nesting tunnels and reduce the chances of wood
decay.
Although carpenter bees are less aggressive than wasps, female bees provisioning their
nests will sting. Treatment is best performed at night when the bees are less active, or
while wearing protective clothing.
Carpenter Bees
HYG-2074-06
Susan C. Jones
Associate Professor, Entomology; Extension Specialist, Household and Structural Pests
Carpenter bees are so named because they excavate galleries in wood to create nest sites. They do not consume
wood. Rather, they feed on pollen and nectar. Carpenter bees are important pollinators of flowers and trees.
Carpenter bees typically are just nuisance pests that cause cosmetic rather than structural damage to wood.
Nonetheless, considerable wood damage can result from many generations of carpenter bees enlarging existing
galleries in wood.
Large carpenter bees belong to the genus Xylocopa. Two native species, Xylocopa virginica and Xylocopa
micans, occur in the eastern United States. There also are a number of native carpenter bees in the western
United States. This fact sheet primarily pertains to X. virginica, which has the common name of carpenter bee.
Figure 1. Carpenter bee. (Courtesy
of Kansas State University.)
Identification
Carpenter bees are large and robust. X. virginica is three-fourths to one-inch long, black, with a metallic sheen.
The thorax is covered with bright yellow, orange, or white hairs, and the upper side of the abdomen is black,
glossy, and bare (Figure 1). The female has a black head, and the male has white markings on the head.
Carpenter bees have a dense brush of hairs on the hind legs.
Carpenter bees somewhat resemble bumble bees, except bumble bees have dense yellow hairs on the abdomen
and large pollen baskets on the hind legs. Various species of bumble bees and carpenter bees are similar in
size. Bumble bees typically nest in the ground whereas carpenter bees nest in wood.
Life History
Carpenter bees are solitary insects that do not form colonies. Male and female carpenter bees overwinter as
adults within their old nest gallery. Adults emerge in the spring (April and early May) and mate. There is one
generation per year.
The males are not long lived, and the female carpenter bee prepares the nest. Gallery construction is a timeand energy-consuming process, and the female will preferentially refurbish an old nest rather than excavate a
new one. When constructing a new nest, the female uses her strong jaws (mandibles) to excavate a clean-cut,
round nest entrance hole on the lateral surface of wood in an exposed or unexposed location. This hole is
slightly less than 1/2-inch wide, approximately the diameter of her body. She bores into the wood
perpendicular to the grain for one to two inches then makes a right angle turn (~90�) and excavates along the
wood grain for four to six inches to create a gallery (tunnel). She excavates the gallery at the rate of about one
inch in six days.
The female bee creates a series of provisioned brood cells in the excavated gallery. The larval provision
consists of a mixture of pollen and regurgitated nectar formed into a ball. The female forms a food ball at the
far end of an excavated gallery, lays an egg on top of the mass, and then walls off the brood cell with a plug of
chewed wood pulp. A female often creates six to 10 partitioned brood cells in a linear row in one gallery, and
she dies soon thereafter. Larvae feed on the pollen/nectar food mass, which is sufficient food for them to
develop to the adult stage.
The life cycle (egg, larva, pupa, adult) is completed in approximately seven weeks, although developmental
time may vary depending on the temperature. The new adults typically remain in their gallery for several
weeks then chew through the cell partitions and venture outside in late August. They collect and store pollen in
the existing galleries, but also spend much of their time just huddled together inside a gallery. These new
adults hibernate in galleries because they require shelter during the winter. They then emerge the following
spring.
Habits
Carpenter bees nest in a wide range of softwoods and hardwoods, particularly if the wood is weathered.
Eastern species of carpenter bees prefer softwoods such as cedar, redwood, cypress, pine, and fir. The bees can
more easily tunnel through woods that are soft and that have a straight grain. Western species of carpenter bees
often nest in oak, eucalyptus, and redwood.
Carpenter bees attack structural timbers and other wood products, including fence posts, utility poles,
firewood, arbors, and lawn furniture. In buildings, carpenter bees nest in bare wood near roof eaves and gables,
fascia boards, porch ceilings, decks, railings, siding, shingles, shutters, and other weathered wood. These bees
avoid wood that is well painted or covered with bark.
The carpenter bee entrance hole in wood may not necessarily be in an exposed area. For example, the inner lip
of fascia boards is a common site of attack. Nail holes, exposed saw cuts, and unpainted wood are attractive
sites for the bees to start their excavations.
Figure 2. Carpenter bee entrance hole
in fascia.
Figure 3. Carpenter bee staining on
siding below the fascia.
Figure 4. Carpenter bee gallery
exposed in wood.
Economic Importance
Despite their beneficial aspect of being important pollinators of many trees and flowers, carpenter bees also
may be nuisance pests around structures. Carpenter bees are noisy, which may be bothersome. These large
bees create alarm when they dive-bomb or fly erratically around humans. In actuality, these are male bees,
which are territorial but harmless because they lack a stinger. Only females have a stinger. Female carpenter
bees are docile and are reported to sting only if handled.
Carpenter bees create a nuisance by excavating round entry holes in wood (Figure 2) and depositing yellowish
to brownish streaks of excrement and pollen on surfaces below entry holes (Figure 3). They also produce
coarse sawdust from their borings. The carpenter bee gallery system is confined within the wood (Figure 4)
and hence is not visible.
Carpenter bee damage to wood initially is minor, and carpenter bees seldom cause consequential structural
damage. However, their repeated colonization of the same wood can eventually cause considerable wood
damage. Carpenter bees preferentially refurbish and enlarge an existing tunnel instead of boring a new one,
and a gallery can extend for 10 feet if used by many carpenter bees over the years.
Carpenter bees sometimes construct new tunnels near old ones, with infestations persisting for several years.
This complex system of tunnels can result in extensive damage to wood. Wood replacement is necessary when
the strength of structural members, posts, poles, and other wood products is reduced due to carpenter bee
damage.
Carpenter bees also may be indirectly responsible for unsightly wood damage when woodpeckers riddle the
wood with holes searching for the developing carpenter bees to feed upon.
Integrated Pest Management
When dealing with carpenter bees, it is preferable to locate tunnel entrances during the daytime, but treat after
dark on a cool evening when carpenter bees are less active. Wear protective clothing to avoid any stings during
treatment.
Prevention
Keep all exposed wood surfaces well painted with a -polyurethane or oil-base paint to deter attack by carpenter
bees. Periodically inspect painted surfaces, because the coatings will begin to deteriorate due to weathering,
leaving exposed wood that the bees then can easily attack. Wood stains will not prevent damage. Consider
using aluminum, asbestos, asphalt, vinyl siding, and similar non-wood materials that are not damaged by
carpenter bees. Seal existing gallery entrance holes to discourage carpenter bees that are looking for potential
nesting sites.
Mechanical Measures
A non-insecticidal management approach is to deny carpenter bees access to their galleries by sealing each
entrance hole. Thoroughly plug the hole with caulking compound, wood putty, or a wooden dowel affixed with
wood glue. If possible, also fill the entire gallery system with a sealant. Carpenter bee galleries are a critical
resource, since the bees spend much of their time inside a gallery, and they require its protective conditions to
survive the winter. Bees that are trapped inside a caulked gallery typically will not chew out due to behavioral
constraints. This barrier approach has promise for reducing future carpenter bee infestations.
In new nests, the single female often can be swatted and killed, or she can be captured and crushed or
otherwise destroyed. Larvae and pupae can be killed by inserting a sturdy wire into the entrance hole and
probing into the gallery as deeply as possible.
Insecticides
A chemical treatment using an appropriately labeled insecticide can protect wood for short periods, especially
in the spring and summer when carpenter bee nesting activity is apparent. Dust formulations typically provide
residual effects and are effective due to the nature of carpenter bee gallery construction. Precisely inject the
dust directly into each nest entrance hole and as deep into the tunnel as possible and also apply it to the
adjacent wood surface. Wait for a few days before plugging entrance holes since adult bees should be allowed
to pass freely to distribute the insecticide within the galleries. Newly emerged bees also will contact the dust
when attempting to leave their gallery.
For use as a preventive, an insecticide should be applied to wood in early spring before carpenter bees begin
excavating nests. The insecticide kills the bees that contact it on the wood�s surface. However, a preventive
approach has limitations because of the difficulty in applying a chemical to all exposed wood on the house
where bees could nest. Furthermore, such insecticides usually degrade in a matter of weeks or months so
repeated applications are needed to maintain a lethal dose of the insecticide. Some pest management
companies report good results against carpenter bees by spraying wood with a microencapsulated pyrethroid,
Demand� CS insecticide (registered for use only by licensed professional applicators), which contains the
active ingredient lambda-cyhalothrin. A number of other pyrethroids (bifenthrin, cyfluthrin, deltamethrin,
permethrin, etc.) also are labeled for use against carpenter bees.
Insecticides that act as stomach poisons, such as borates, typically are ineffective against carpenter bees, which
do not ingest the wood that they excavate.
Click here for PDF version of this Fact Sheet.
Bumble Bee or Carpenter Bee?
When encountering black, almost round bees buzzing around
their home most people do not know the difference between the
bumble bee and carpenter bee. There are two basic things to
note that should quickly let you know which bee you are seeing:
location and activity of bee and certain physical characteristics
of the bee.
Carpenter bees are most often noticed while they are building and tending to their nests
which are simple, round openings in wood structures. If you see a bee that is boring out a
perfectly round hole in wood, it is a carpenter bee. For more information about carpenter
bees (biology, habits, how to control) go to the Carpenter Bee web page.
Bumble bees have a fuzzy abdomen and the Carpenter Bee has a shiny abdomen.
General Bumble Bee Information
The "Bumble Bee" is a big, hairy, black and yellow bee whose size can range from 3/4 inch
to 1 1/2 inch. This insect is often mistaken for a carpenter bee, which closely resembles the
bumble bee in appearance. Carpenter bees have a shiny and smooth abdomen as opposed
to the fuzzy abdomen seen on a bumble bee.
There are over 200 types of Bumble bees in the world. Fifty different types can be found in
North America. Each different species will have its own preference to types of nectar and
prefers different flowers.
The bumble bee is an important, beneficial insect. They pollinate plants and flowers as
they forage for food. To gardeners, it is a welcome sight to see these large, flying insects
carrying large loads of pollen, flying into and around their flower beds and gardens. While
busy searching for food (and at the same time, pollinating plants) bumble bees are rarely a
problem when in close proximity to humans. They will actually (in most cases) go out of
their way to avoid human contact. Bumble bees will, however, defend themselves if they
sense that they are cornered and cannot escape. Most of the time they will fly away from
danger but will sting if they are under duress.
Bumble bees have very few predators in nature. Skunks are their largest and most
destructive predator. Skunks are omnivores that will eat insects, rodents, reptiles, small
mammals, worms, eggs, fish, fruit, and plants. When they locate a bumble bee nest, skunks
help themselves to bee larvae and adult insects. They ignore the pain of bee stings to get to
their preferred foods.
The queen bumble bee comes out of hibernation every spring to find a new spot to build
her nest and start a new colony. This queen bee was fertilized the previous season and has
managed to live through the winter months.
The same nesting spot (from previous seasons) are rarely used. A suitable place for nesting
is usually on the ground, beneath a flat object. An old mouse hole or similar hole in the
ground is preferred if it is underneath an old tarp, flat stone or man made objects such as a
deck. The hole chosen by the queen bee is first padded by pieces of vegetation such as dry
grass or moss.
It is in this padded underground hole that the fertilized queen bumble bee lays her eggs
and begins collecting nectar for her soon to hatch grubs. On the grubs emerge from their
eggs, the queen bumble bee spins a protective silk cocoon for each grub. It is from this first
batch of larvae that 5 to 20 daughters emerge. These daughters of the queen bumble bee
are workers who begin immediately start working on building the colony. The queen bee
will continue to lay eggs for the remainder of the summer season. The workers work
tirelessly to build the colony, collect nectar for the young and also to provide protection for
the colony. The first batch (or hatching) of bumble bee workers are smaller than their
sisters who will emerge later on when the colony grows larger and healthier. The queen
bee uses her energy to begin the nest and this energy (as well as time) is spread thin as she
is the sole worker for the new colony. As the colony grows, the eggs and larvae are given
more attention and food simply because there are many workers that share the work load.
It is at this point in time that larger bumble bees are seen.
Bumble bees are often first noticed (in the area of the nest) when this activity of guarding
the nest and pollen collecting begins. The worker bees are focused only on their job and
will not go out of their way to sting people. It is only if people get too close to their nest or
threaten them when bumble bees will sting. Bumble bees do not die after stinging, as do
some other stinging insects.
Towards late summer, the queen will start to produce drones and young queens. The
young queens are fertilized by the drones, then fly off to hibernate. Hibernation usually
takes place in dry protected areas such as loose bark. The colony's remaining drones and
workers stay in the colony and die during the winter season. The young queens start new
colonies in the spring of the year. As mentioned above, bumble bees do not use the same
nest though they may nest in an area close by to the original bee nest.
Bumble Bee
Photo by:
Dorling Kindersley
Bumble Bee, common name for any of a group of large, hairy, usually black-and-yellow, social
bees. They are found primarily in temperate regions of the northern hemisphere, often ranging
farther north and higher in altitude than other bees. Fifty species of bumble bees are known in
North America.
Characteristics
Bumble bees are similar to their close relatives, the honey bees, in that their colonies are headed
by a queen, who is the main egg-layer, and many workers, who are the daughters of the queen,
and in that drones (males) are produced during the mating season. However, the colonies of
bumble bees, unlike those of honey bees, only survive during the warm season; new queens
hibernate alone to begin another colony the following spring. In addition, there are usually fewer
individuals in a bumble-bee colony than in a honey-bee colony, and bumble bees do not use a
dance to communicate the location of food to other members of the colony, as honey bees do.
Also, although bumble bees collect nectar and store it as honey, they do not hoard large amounts
of it, as do honey bees.
Because bumble bees are conspicuous and important in nature, their biology has been well
studied. They are among the few insects that can control their body temperature. In cold weather,
queens and workers can shiver their flight muscles to warm themselves, allowing them to fly and
work at lower temperatures than most other insects. Their large size and heat-conserving hairy
coats also help them stay warm. These features enable them to live in northern latitudes and
alpine altitudes. Bumble bees are sensitive to habitat disturbance. In England, several species are
thought to have become extinct in past decades due to land clearing and agricultural practices.
Life of the Colony
The bumble-bee nest consists of a spherical chamber with a single exit. The queen chooses a
preexisting cavity, such as an abandoned mouse nest, in which to begin her family. Most species
nest in the ground. The queen forms a small mound of pollen paste in the middle of the nest, lays
several eggs in it, and seals it with a small dome of wax. She also constructs a hemispherical wax
cup, called a honeypot, in the entranceway floor and fills it with nectar. The queen feeds on this
nectar while she incubates the eggs. The newly hatched larvae partially consume the paste in
their cells. Later they are fed by the queen through a small opening in the cell wall. When the
larvae are fully grown, they spin cocoons in which they metamorphose, eventually emerging as
the first workers of the new colony. Subsequent larvae are reared by these workers in individual
cells, much as honey-bee larvae are; however, the bumble-bee nest is not organized into flat,
vertical combs like that of honey bees but grows instead into a mound of capsule like cells.
Toward the end of summer, the queen begins to lay unfertilized eggs that develop into drones.
Female offspring produced at this time become new queens, and mating takes place soon
afterward. The drones and workers then die, and the new, mated queens fly off in search of safe
places to hibernate.
Some species of bumble bees, known as cuckoo bumble bees, are parasitic on the nests of
nonparasitic bumble bees. They invade the nest, kill the resident queen, and force the workers to
raise the young parasitic bees along with the brood of the host colony. Occasionally, the invaders
permit only their own young to survive. Cuckoo bumble bees lack pollen baskets because they
do not forage for pollen.
Pollination
Bumble bees are important pollinators of many plants. Both queens and workers collect pollen
and transport it back to the colony in pollen baskets on their hind legs. Workers are small if born
early in the year, and large if born later in the year. Also, some species of bumble bees are larger
than others. Differences in body size, and especially in tongue length, are important in
determining which flower species a bumble bee will visit for nectar and may determine which
flowers it can pollinate.
Bumble bees have long been recognized as vital to the production of certain seed crops. In recent
years, bee scientists have developed a means to cause queens to skip their winter hibernation and
produce colonies year-round. This has made certain species of bumble bees available for use in
pollinating crops they did not before. Bumble-bee colonies are now used extensively in
greenhouse pollination of crops such as tomatoes and strawberries.
Reproduction and Life Cycle of the Yucca Moth
Male and female Tegeticula yuccasella moths use the yucca blooms as a bridal chamber,
with the male abdicating all responsibility for the female and the larvae after mating. Mating
occurs in the evening hours when the yucca blooms are fully open.
When the yucca plant begins its spring bloom, signaling its readiness for pollination, the
yucca moth, using her specialized mouth organs, collects the highly adhesive pollen from
the yucca flowers' male sex organs, or anthers. Typically secretive - the female yucca moth
works only in the darkness between sunset and midnight - and choosy - she seeks the
newest of blooms - the yucca moth, once pollen laden, now enters a flower and circles and
evaluates the female reproductive organ, or ovary. She may withdraw and renew her search
if she finds that another yucca moth has visited the flower ahead of her. Once she makes a
choice, she lays eggs in a specific location within the flower's ovary. She then climbs the
ovary's stigma and deposits a small fragment of her pollen, fertilizing the flower so that it
soon begins producing fruit and the seeds for her coming offspring. With only a few days
left in her lifetime, she soon moves on, searching for another acceptable bloom.
The yucca moth’s larvae hatch within several days, with the yucca plant - keeping its end of
the bargain - providing its fruit for housing and some seed for food. When conditions are
right, ideally soon after a nighttime thunderstorm, the yucca moth larvae leave the fruit of
the yucca and drop to the desert soil. They burrow down one to three inches. Each creates a
cocoon, where it may develop for several weeks to several years before it emerges to renew
the cycle.