The monarch butterfly is native to North, Central, and northern South America. It has been accidentally introduced to numerous islands in the Pacific and Atlantic.
In the spring and summer, the monarch butterfly's habitat is open fields with milkweed. In the fall, monarch seek forested areas with a specific microclimate-overnight temperatures above freezing but cool in the daytime.
Monarch butterfly larva feed on milkweed. Adult gather nectar from flowers. Because most milkweeds contain bad tasting chemicals (glycosides) that are incorporated into the adult, monarchs are distasteful to predators.
Monarchs mate for the first time when they are three to eight days old. Mated pairs remain together for up to 16 hours-from afternoon until early the next morning. Both sexes mate several times during their lives.
A female prefers to lay eggs on young milkweed plants, mosts often on the underside of the leaf. By scattering eggs over many plants, monarchs increase the chance that some of their offspring survive.
The egg hatches in three to four days and the young caterpillar eats its own eggshell as its first meal.
The larva devours milkweed leaves. Monarch larva do not feed on any other plants, although they do eat many different species of milkweed.
The caterpillar molts, or sheds, its exoskeleton (skin)four times as it grows. The interval between each molt is called instars. The larva goes through five instars. During each instar the body grows, but the head size stays constant.
The larva eats voraciously for about two weeks and grows to approximately two inches in length. The fully grown larva seeks out a place to begin pupation.
The larva finds a location under a leaf or overhang, attaches itself with hooks in the last pair of legs to a silken pad, and forms a pre-pupal "j" before shedding its skin for the last time.
The larva splits its exoskeleton and wiggles out of its old skin, revealing the new skin (cuticle) of the pupa. The cremaster, a spiny appendage at the end of the abdomen, hooks into the silk pad as the larva skin is shed.
The chrysalis (pupa)stage last for approximately two weeks. The mature butterfly becomes visible through the pupal cuticle during the last twenty-four hours of this stage.
The fully developed butterfly within the pupa performs a series of contractions to expand the pupal cuticle. The contractions split the covering and allow the butterfly to emerge. Upon emergence, the butterfly begins to inflate its wings to a full size.
After a few hours, the adult monarch butterfly begins to fly and to gather nectar from flowers. Adult monarchs feed on nectar and water for the remainder of their lives. The life cycle from egg to butterfly takes approximately four to five weeks. The main function of the adult is to reproduce — to mate and lay eggs that will become the next generation.
Male: thin veins on wings and pronounced black spot.
Female: Characterized by thick veins on wings and no black spots.