NATIVE
POLLINATORS: An Introduction
copyright
© 2002 k.Ruby
Most people know that plants reproduce through
pollination and setting seed. We are less aware that flowering plants depend
on the services of an insect or animal pollinator to transport the male genetic
material (pollen) to the female reproductive organs of another plant of the
same species. There are many thousands of insect pollinators such as beetles,
butterflies and moths and animal pollinators such as hummingbirds and bats,
but bees (hymenoptera) are the most prolific and efficient of the pollinators.
Their bodies are covered with fine hairs and physical structures designed specifically
for pollen collection. There are over 25,000 species of bees worldwide and 4000
native species counted in the US.
Bees are generally divided into several categories. There are social and solitary
bees, generalist and specialist bees. Honey bees are the only truly social bees.
They live year round within a social structure, called a colony or hive, with
a clear division of labor and they care for their young. The honey bee (apis
mellifera) is native to Europe, but has naturalized worldwide.
Bumble bees, some species of which are native to the US, are in the same genus
as the honey bee and are considered semi-social. The queen bee builds a seasonal
colony which works and lives together during the warm months of food abundance
and dies out over the winter (mature bees overwinter in a dormant state waiting
to hatch in the next warm season). Bumble bees are important pollinators and
have a special relationship to certain plants who will only release their pollon
through the strong vibrations of the honey beeës buzz. In particular bumble
bees are pollinators for some plants of the Solanaceae family and are often
used commercially as pollinators in tomato hothouses.
All the other bees are solitary bees. They
may share nesting areas, but they build and live alone and do not tend their
young once the egg is laid. Among these bees are the mason bees, carpenter bees,
plasterer bees, digger bees and carpenter bees. They range widely in size and
shape and in the manner of building their nests. Nests are commonly built in
snags (dead wood) or directly in the ground and are lined with gathered material
such as leaves or mud. The female bee hatches, mates and sets about building
a nest. For each cell she collects pollen and mixes it with nectar to form a
perfectly round pollen ball. This ball or Ñbee breadì as it is
often called, is deposited into a cell and a single egg is laid on top of it.
The bee then closes the cell and leaves. Nests can range from one to sixty cells,
depnding on the species. Once the egg hatches, the larva eats, poops and pupates.
Depending on the species and the time of year the mature bee will then emerge
and start the cycle over, or over winter in a semi dormant state, waiting for
the right weather conditions. They will often emerge just at the moment that
their prefered host plant is coming into bloom!
Bees offer their pollination "services" for plant "rewards"
of pollen and nectar. Some bees are generalists and can gather and claim rewards
from a variety of plants. Others are specialists who have developed an evolutionary
relationship with a particular plant. Many times their life cycle and physical
structures are attuned to this plant in such a way that the two are dependant
on eachother for their further existance. If one or the other is endangered
both are endangered. Thus if a plant habitat is diminshed in such a way that
less bees visit them, pollination does not occur and their seed set is also
diminshed. The population may dwindle to the point that bees no longer come
to offer their services or die out completely along with their prefered plant.
Conversely, if the bee habitat is disrupted, by clearing of dead wood and brush
or through constant disruption of the soil through tilling, there may not bee
enough bees for effective pollination.
Habitat fragmentation of this sort is a reality in the US. Entire plant species
can be destroyed when an area is cleared for a housing project. Fortunately
native bees can be quite enduring. Even specialist bees can learn to survive
on other plants than their prefered plant. Bees will Çcome back to an
area that has been decimated given the right conditions and can exist quite
well even in an urban setting given enough of the right kind of habitat. In
a recent study by UC Berkeley professors and botanists, 72 native bee species
were counted in the Berkeley area alone.
Native bees need much the same things as we do; shelter. food and water. bee
habitat can be provided by creatively arranging stumps or other deadwood in
your garden and by leaving exposed earth in perenial plant beds unturned. You
can also create bee habitat by drilling holes into scrap lumber. Naive bees
prefer a range of diameters between 3/16th and 5/16th and between 4 and 8 inches
deep. Due to selective color vision bees like flowers in the white, yellow,
blue and purple ranges. There are many many native and exotic plants that will
draw bees to your yard. Among them are mints, lavenders, yarrow, clarkia, gaillardia,
delphinium, poppies, penstamon, milkweed, ceonothus, grindelia, fireweed, verbena
and dusty miller. To provide and maintain a regular visiting spot 2 to 3 square
meters of plant material seems to be a good minimum. If you provide water in
a small pond or bird bath, be sure that there are plenty of landing areas for
the bees. Flat rocks or sticks that angle gradually into the water are excellent
for this purpose.
Native bees are a vital link in the cycle of life and their role in the continuance
of these cycles is often underestimated. Every time a species becomes extinct
we loose access to valuable information and wisdom contained in the gene sequence.
Gene pool diversity is not only important to human applications, it is valuable
in itself. Once that information is lost, we can no longer get it back and we
can only wait and see how this loss may effect the entire web of life on the
living organism that is this planet. We have a choice to support life or destroy
it. Creating habiat for bees and plants is a small part of a bigger solution.
Happy Pollinating!
FYI. All female bees ahve the capacity to sting.
No male bees can sting. Most bees, when left to themselves and unthreatened
will not sting. If a bee approaches you, it is possible that you smell good
to them, like a flower! If you walk away calmly and avoid making abrupt movements
you will also most likely avoid a sting.