14.2. Danaus plexippus: Monarch Butterfly http://www.ck12.org
Habitat
The monarch butterfly population is split into two sides of the United States; the two sides are the east and west of
the continental divide. They live in milkweed plant communities. They live in places with warm temperatures. The
population on the eastern side spends its winters in Mexico, and the rest of the year in the United States and Canada.
In winter they can be found in high altitudes in Central Mexico. The population on the western side of the continental
divide can be found in Idaho, Utah, Arizona, Colorado, and California in the summertime. At the end of summer
the butterflies migrate back towards the coast, and they stay in areas ranging from Baja to San Francisco. When they
migrate, they look for big tall trees like eucalyptus trees. During the winter, the butterflies live on moisture and body
fat until milkweed grows again in the spring, and then they fly inland.
Biology
There are four stages in the life of the butterfly. The four stages are:
- Egg: The first stage is an egg. This butterfly will only lay it’s eggs on milkweed plants.
- Larva: The second stage is when the caterpillar hatches from the egg. It is hard to see at first, but later within two
weeks it gets to be a few inches long. Usually the caterpillar has stripes or a pattern on it of yellow and black, and it
has to keep shedding about 4 or more times. Caterpillars need to eat a lot. - Pupa: After the caterpillar has grown to a certain size, it makes itself into a light green chrysalis and changes
inside. - Adult: The last stage is the butterfly stage. Adults reproduce in this stage.
Cell Biology
Like all other plants and animals, the monarch butterfly has eukaryotic cells. Eukaryotic cells have a nucleus and
many other organelles. New cells are made when existing cells grow and divide. Some reasons cells divide are that
they have to repair tissue, growth, or reproduction. Mitosis happens when the nucleus of the cell divides, and two
new cells with the same DNA as the original one are formed.
Meiosis is cell division in which gametes (example: egg, sperm) are made with half the chromosomes of the original
cell. Chromosomes are made of DNA with genes that have “codes” for the butterfly’s traits.
Evolution
Scientists say that the butterflies separated from moths 150 million years ago. Butterflies are in the moth family.
Ecology
Some predators of the monarch butterfly are wasps, bees, snakes and birds. The predators who eat the monarchs
won’t want to eat them again because they don’t like the taste. The monarch butterfly eats the milkweed plant (as
a caterpillar), which gives the butterfly a strange taste to its predators. The predators don’t like the strange taste.
Their unique color of orange and black make them stand out and will keep predators away. The bad taste, together
with the bright colors provide a successful defense mechanism. Monarchs share the defense of bad taste with the
similar-looking viceroy butterfly in what is perhaps one of the most well-known examples of mimicry. Mimicry is
the similarity in appearance of one species to another which protects one or both of them.