In addition to being beautiful, monarch butterflies have an amazing life cycle. Many people—students, naturalists, scientists
and others—have made it their life’s work to learn more about this incredible insect!
In the entire world, no butterflies migrate like the monarchs of eastern North America. Individuals travel much farther than
all other tropical butterflies, up to 2,000 miles.
Monarch females can lay several hundred eggs, usually laying a single egg on a plant. The eggs hatch about four days after
they are laid.
Monarch caterpillars eat plants only in the milkweed family. There are over 100 known species of milkweeds in North America.
Monarchs have been reported to feed on 27 of them, but they undoubtedly feed on others as well.
Adult monarchs drink nectar from many species of flowers. Nectar contains sugar, which serves as the main energy source for
Monarchs have an effective chemical defense to protect them from predation; when they eat milkweed, they sequester the poisonous
cardiac glycosides in the milkweed. Cardiac glycosides are poisonous to vertebrates; as a result, most monarchs face little
predation from frogs, lizards, mice, birds and other species with backbones. Their bright colors also serve as a warning to
predators that they contain these poisonous chemicals.
Several species of birds—most particularly black-headed grosbeaks and black-backed orioles—can eat adult monarch
butterflies in the overwintering colonies. While grosbeaks are relatively insensitive to the cardiac glycosides, the orioles
have figured out which parts of the monarch bodies are safe to eat and avoid the most poisonous parts. Grosbeaks and orioles
can kill more than 10% of the total monarch populations in a winter.
The monarch caterpillar stage is also known as the larval stage; the caterpillar is an eating machine, taking few breaks even
The monarch larva molts, or sheds its skin, five times before entering the pupae stage. The entire larval state lasts from
9-14 days under normal summer temperatures.
The pupa stage is often called a chrysalis and usually lasts from 8-13 days (the lower time corresponds to warm conditions.
It is not a cocoon, since it has no silken covering.
Male and female monarchs are easily distinguished: males have a black spot on a vein on each hind wing that is not present
on the female.
Adult monarchs in summer generations live from 2-5 weeks; those that emerge in late summer and early fall can live up to 8-9
months to survive the trip to and from their overwintering sites in Mexico.
Most monarchs found east of the Rockies winter in the Transverse Neovolcanic Mountain Belt in Mexico; those found west of
the Rockies winter along the California coast where they roost in Eucalyptus trees, Monterey pines and Monterey cypresses.
California monarchs make up about 5% of the overall worldwide monarch population.
In Nahuatl, an indigenous language of Mexico, butterflies are called 'papalotl' . From this word comes the Spanish word for
kite: 'papalote'. Monarchs are known as kites of the mountains.
Monarch butterflies are found throughout the U.S., in southern Canada, Caribbean Islands, Australia, New Zealand and other
In 1983, the IUCN Invertebrate Red Data Book designated monarch migration a threatened phenomenon.
Not all monarchs migrate. There are continuously-breeding populations throughout the New World tropics and the Caribbean that
remain in the same place throughout the year.
When monarchs migrate, they are in a physiological state called "reproductive diapause," or arrested sexual development. These
monarchs will not mate or lay eggs until their diapause ends in the late winter or early spring.
Monarchs use "thermals," or updrafts of warm air, to allow them to glide as they migrate, thus conserving energy for their
long flight. Migrating birds also use thermals.
Monarchs are in the butterfly family Nymphalidae. Members of this family appear to have only 4 legs, but they really do have
6; their front pair of legs is greatly reduced in size and tucked up under their head.
Mating monarchs remain in copula for up to 16 hours. During that time, the male transfers nutrients to the female, along with
sperm. These nutrients are used by the female in egg production.
Spiders, mites, ambush bugs, ants, lacewings, wasps and stinkbugs all eat monarch eggs or larvae.
Monarch larvae, like other caterpillars, have very poor vision. They see through six pairs of simple eyes, called ocelli.
The long black tentacles on monarch larvae are not antennae. The antennae are very small and are on the bottom of the larval