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By Marna Towne (Mrs_Ed)
October 18, 2012
In Dave's Garden newsletter
Lure these gorgeous
black and orange beauties into your yard with the right plants.
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In more recent times however, the Monarch
butterfly population has declined. Like other butterflies, habitat destruction and pesticide use are often the
culprits. While gardeners often supply nectar plants for all butterflies, some
are unaware of the needs of the Monarch larva. Many others simply do not know
or understand the impact of a simple act like mowing a patch of milkweed has on the Monarch.
As the saying goes — Knowledge is Power.
Let's go back to science class for a Monarch Butterfly Lesson.
Identification
The Monarch is one of the most identifiable
butterflies in the United States. It's orange and black wings stand out
brightly in the summer blue sky, while its size makes it viewable from a
distance. The Viceroy possesses similar colors and veining — an
extra horizontal strip on its lower wings readily distinguishes this butterfly
from a Monarch. The Monarch below center shows two oval spots on the lower
wings. These are scent glands that can be seen from the front or back of the
wing and indicate that this butterfly is a male. Additionally, females have
thicker black veining to distinguish them.
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Like most butterflies, Monarchs experience
four stages in their month long life cycles — egg, larva, pupa and adult.
Females lay eggs on host plants (milkweed, see below). The oval eggs are about
the size of the head of a pin — large enough to be seen by the unaided eye.
Approximately four days after eggs are laid, the larva will begin to eat its
way out of the hard shell by eating the shell itself.
In the larval or caterpillar stage, the
Monarch undergoes five phases, or "instars" lasting nine to 14 days.
The body of the caterpillar features a head, abdomen and thorax. They have six
pairs of eyes but their vision is poor. To aid them in sensing their way around
the milkweed, they have front and rear tentacles. They breathe by taking in
oxygen through holes in the sides of their bodies.
During their phases the Monarchs are eating
machines, growing so large between phases that they must shed their skin. The
molting starts at the head and peels back to the rest of the body. The
caterpillar then eats this shed skin before continuing to eat more milkweed.
When a Monarch is ready to pupate, the
caterpillar crawls to a spot where it can hang and form a chrysalis. First it
makes a silk pad (on a branch or such) to which it attaches its rear end by a
spike called the "cremaster." They it forms a "J" shape and
begins to split its skin for the last time (to see a wonderful pictorial
display of this, check out the pictures from 'kennedyh' in the Bug
Files). This last skin is the "chrysalis" — it begins soft but later
hardens. During this stage, the Monarch must continue to hang to form properly.
When it is close to emerging, the wings will develop their orange and black
pigment and the pupa will darken.
The adult Monarch emerges in 10 to 14 days.
The wings are still wet at this time and need about three to four hours to dry.
After this waiting period, the adult butterfly is ready to fly, provided
temperatures are warm enough (60º). Summer adults are ready to mate in three to
eight days and the process begins all over again. The summer adult Monarch
lives from two to five weeks. The last generation of the summer however live
much longer, about nine months, in order to migrate and reproduce in the spring.
Eastern Population Migration
In late summer and early fall a portion of
the North America Monarch butterfly population migrates south. Some from the
east coat overwinter in southern Florida, but most find their way to the
mountains of central Mexico. The University of Kansas Biological Research
department operates Monarch Watch, a Monarch butterfly
education and research program. According to Monarch Watch, migration dates begin in Canada as early
as August 18th. By October 10th, Monarchs in Houston, Texas will begin their
journey south.
The Monarch Lab at the University of
Minnesota offers wonderful research on the fall migration. They cite day
length, temperatures and host plant quality as factors in creating the
physiological differences in late season Monarchs. These Monarchs are those
that will make the journey south where can overwinter. Journey North, an educational site
monitoring seasonal change, tracks both fall and spring migrations of Monarch
butterflies. Tracking for Journey North’s 2008 fall season begins August 28th.
The winter roosts in Mexico (and in California for western populations)
enable scientists and researchers to monitor and provide colony counts each
year. With this data, researchers can see population growths and decline from
each year. When the overwintering Monarch's make their trip back north into
Texas in March, they will produce the first generation of the year and die.
This first generation will continue the migration north through June.
Habitat
Monarch butterflies can be found in many
habitats: country roadsides, suburban gardens even city parks. If they find a
source of both nectar and host plants, the Monarch will be happy. Host plants
are those on which the female butterfly lays her eggs and on which the
caterpillars will feed. For Monarch butterflies, the host plants are those
within the Milkweed (asclepias) family.
My Mother tells a story about walking
country roads as a child and collecting the silky portions of seeds from
milkweed pods. The silk was used for life preservers for World War II
servicemen. Growing up, this common milkweed (Asclepias syriaca) was the only
milkweed that I ever knew about. According to the U.S. Government however, there are over
100 species of milkweed — a portion are known important hosts for Monarchs. .
Monarch Watch offers the "Monarch Waystation Program" to help
increase and protect Monarch habitats. They encourage citizens to develop
Monarch Waystations in any areas possible (gardens, parks, schools, roadsides,
unused plots, etc.) This program hopes to restore milkweed habitats and provide
feeding stations for migrating butterflies. Waystations sites may be certified
and/or registered and provide wonderful educational opportunities. The program
sells seed kits of the following host and nectar plants. If you are looking to
entice Monarchs to your garden, these plants are ideal choices.
Butterfly Weed
Milk Weed
Cosmos
Joe Pye Weed
