Transcript monarch butterflies go through four generations each year

1. Monarch butterflies facts
Monarch butterflies are the most beautiful of
all butterflies, some say, and are considered
the “king” of the butterflies, hence the name
“monarch”.

Did you know that monarch butterflies go
through four generations each year?
The first three generations hatch from their
cocoon state (also known as the pupa or
chrysalis state) and live for up to six weeks,
but the fourth generation continues to live
on for up to six or eight months so that they
can migrate to a warmer climate, hibernate,
and then start a new first generation in the
spring time.

Did you know that the monarch
butterflies that live in North America
migrate? Monarch butterflies are the only
insect to migrate up to 2,500 miles to get
out of the cold weather and hibernate. But
not all monarch butterflies migrate; only the
fourth generation of monarchs can migrate
each year because the first three
generations die after about six weeks from
escaping their cocoons.

Did you know that monarch butterflies
are poisonous? They won’t harm humans,
but the chemicals from the milkweed plant
that they eat when they are in the larvae
stage builds up inside of them and gives
them a poisonous defense against
predators like frogs, birds, mice and
lizards.

Do you know how to tell a male from a
female monarch butterfly?
Female Monarchs have darker veins on
their wings, and the males have a spot in
the center of each hind wing from which
pheromones(信息素) are released. Males
are also slightly larger.
Female
Male

2. Monarch butterfly life cycle
Monarch butterflies
go through four
stages during one
life cycle. These
four stages are the
egg, the larvae
(caterpillar), the
pupa (chrysalis),
and the adult
butterfly.
Adult female
monarchs lay their
eggs on the
underside of
milkweed
leaves. These
eggs hatch,
depending on
temperature, in
three to twelve
days.
A milkweed plant

The monarch butterfly is sometimes called the
“milkweed butterfly” because its larvae eat the
plant. In fact, milkweed (马利筋) is the only
thing the larvae can eat!
A
monarch
butterfly
on
milkweed

Note:
Once a monarch butterfly is an adult
(after the metamorphosis into a full
grown butterfly) it can eat the nectar
from any flower, not just the milkweed
plant. Only the caterpillars need the
milkweed plant to live.
The larvae
feed on the
plant leaves
for about two
weeks and
develop into
caterpillars
about 2
inches long.
A monarch caterpillar
After awhile, the caterpillars attach themselves
head down to a convenient twig, they shed
their outer skin and begin the transformation
into a pupa (or chrysalis), a process which is
completed in a matter of hours.
a
Monarch
pupa
The pupa resembles a waxy, jade vase and
becomes increasingly transparent as the
process progresses. The caterpillar
completes the miraculous transformation into
a beautiful adult butterfly in about two weeks.
The butterfly finally emerges from the now
transparent chrysalis. It inflates its wings with
a pool of blood it has stored in its
abdomen. When this is done, the monarch
expels any excess fluid and rests.

The butterfly waits until its wings stiffen and dry
before it flies away to start the cycle of life all
over again.
3. Migration of Monarch Butterflies

Monarch butterflies are not able to survive
the cold winters of most of the United States
so they migrate south and west each autumn
to escape the cold weather. The monarch
migration usually starts in about October of
each year, but can start earlier if the weather
turns cold sooner than that.

Eastern populations winter in Florida, along
the coast of Texas, and in Mexico, and return
to the north in spring. Monarch butterflies
follow the same migration patterns every
year. During migration, huge numbers of
butterflies can be seen gathered together.
Those orange
things in the
picture are
not autumn
leaves...
they're
hundreds of
Monarch
butterflies!

The monarch butterflies will spend their
winter hibernation in Mexico and some parts
of Southern California where it is warm all
year long. If the monarch lives in the
Eastern states, usually east of the Rocky
Mountains, it will migrate to Mexico and
hibernate in fir trees. If the monarch
butterfly lives west of the Rocky Mountains,
then it will hibernate in and around Pacific
Grove, California in eucalyptus (桉树) trees.

Monarch butterflies use the very same
trees each and every year when they
migrate, which seems odd because they
aren’t the same butterflies that were there
last year. These are the new fourth
generation of monarch butterflies, so how
do they know which trees are the right ones
to hibernate in? Monarch butterflies are the
only insect that migrates to a warmer
climate that is 2,500 miles away each year.

The Monarch butterfly migrates for 2
reasons. They can not withstand freezing
weather in the northern and central
continental climates in the winter. Also, the
larval food plants do not grow in their winter
overwintering sites, so the spring generation
must fly back north to places where the
plants are plentiful.