Pacific Grove Monarch
Conservancy :: Life Cycle
After mating up to 3 times each, the male Monarch will
die, and the female Monarch flies almost 100 miles to find milkweed. A female Monarch is capable of laying hundreds of eggs and only deposits them on very toxic milkweed plants. She approaches new, tender milkweed plants and taps the top of each leaf to test the toxicity of the plant.
If it is strongly poisonous, she deposits a single egg on the underside of the leaf, moving on to test another leaf and lays a single egg under it as well. In this way, she guarantees that the
caterpillar
that emerges will have plenty to eat, and it will be protected from
predators by becoming toxic from eating the milkweed. This toxicity will continue through the entire
metamorphisis, thus the
adult butterflies are also poisonous, and thus protected from
predators. Scientists are able to genetically trace the butterflies
during migration by knowledge of the species of milkweed the butterfly
fed upon as a caterpillar.The newly hatched caterpillar (larva) immediately eats the eggshell from which it emerged, then voraciously feeds on the milkweed host plant for 10 to 20 days. During that time, the caterpillar must shed its yellow, black and white striped skin four times as it expands from 1/16th of an inch to about 2 inches in length, and increases its weight by a factor of 2,700 times.
After it has reached its full size, the caterpillar spins a
sticky button called a cremaster on or near the milkweed and attaches
to the button by its rear claspers, letting go with all its legs and
hanging for about a day in a "J" shape. During this time many changes
take place within the body of the catterpillar. Then the caterpillar
sheds its skin for the fifth and last time, kicking the entire
caterpillar body off (head, eyes, antennae, stripes and legs),
revealing the chrysalis forming.
The chrysalis at first resembles a sticky, wet jellybean with yellow
stripes. During the first hour, the stripes move upward and form a
crown of gold buttons near the top and down a side seam. The hardening
chrysalis looks like a jade jewel and hangs quietly for approximately
10
days. Slowly the chrysalis becomes more and more transparent until the
orange and black pattern of the butterfly within is revealed. The
butterfly is ready to emerge from its chrysalis.
As soon as the chrysalis splits open along the seam, a Monarch, with an
enlarged abdomen and very crumpled wet wings, emerges. Immediately, the
Monarch begins to pump fluid from its abdomen into the crumpled wings
along all the black lines which become veins. This action causes the
wings to fully expand and flatten until they are perfectly formed. The
Monarch stays very still for approximately three hours to let its wings
dry and harden. The butterfly is now a fully grown, adult Monarch.Photos courtesy Sally Herrgott
