Friday, September 24, 2021
Friday, September 10, 2021
Monarch butterflies are an iconic species in the United States! These bright orange and black butterflies are known for their migration in North America. How do these small creatures make the 3,000-mile journey every year?
While the bright orange butterflies can be hard to miss,
Colorado has a variety of orange-colored butterflies. You can identify a
monarch butterfly by the black veins on the wings in addition to the bright
orange color. They also have white spots on the edges of the wings. The
wingspan usually ranges from 3-4 inches long. You can identify if the butterfly
is a male or female by looking at the hind wing. If the butterfly is a male, it
will have one black spot on each hind wing along one of the center veins. If
the butterfly is female, she will not have a spot.
Monarch caterpillars have contrasting black, yellow, and white stripes on their body. Caterpillar size varies depending on what instar, or stage of growth the caterpillar is in.
|A female monarch butterfly. Photo: Lisa Mason
All butterflies including monarchs go through a lifecycle called metamorphosis that includes an egg, caterpillar, a pupa called a chrysalis, and an adult butterfly. When monarchs are caterpillars, their job is to feed as much as possible. They feed exclusively on milkweed plants (Asclepias spp.). Once they have fully grown, they will find a safe space to form a chrysalis. The chrysalis is a protective covering for the caterpillar while it transforms into a butterfly. It begins as a pale green color, then gradually turns black and orange as the butterfly gets ready to emerge. After emergence, the butterfly will soon search for a mate and the female will begin laying eggs on new milkweed plants.
|A monarch caterpillar. Photo: Lisa Mason
Adult butterflies only live two to five weeks. The only
exception is the overwintering generation of monarchs that can live up to nine
months in Mexico. Once spring arrives, this overwintering generation will migrate
north to Texas and surrounding areas. The females will lay eggs for the next
generation. Once the next generation becomes adult butterflies, they continue
to migrate north. After a few weeks, they will lay eggs for another generation
further north. Typically, monarchs will have two to three generations
throughout the summer season. Once fall arrives, the fourth generation, also
known as the overwintering generation, will begin to migrate south back to
How does each generation of monarch know how to navigate
migration? For other migratory species like Swainson’s hawks, they follow their
parents and large groups of hawks to the overwintering grounds in Argentina.
Scientists are still researching how monarchs are able to migrate to the same
location every year. Recent research suggests they use a combination of the
sun’s position in the sky, landmarks like mountains, and an internal magnetic
compass. Genetics may also play a role in the ability to navigate.
Monarchs have two migratory pathways in North America. The
eastern monarch population migrates from Mexico up north through the Midwest
and eastern US. The western monarch population migrates from the Pacific Coast
of California to the states west of the Rocky Mountains. While Colorado is not
one of the main migratory corridors, you can still see monarchs throughout our
Other species look similar to the monarch butterfly include
the queen butterfly (Danaus gilippus)
that hosts on milkweed and dogbane plants in the Apocynaceae family, and the
viceroy butterfly (Limenitis archippus)
that hosts on plants in the Salicaseae family including willows, cottonwoods,
These three butterflies look similar for one reason:
mimicry! The contrasting orange and black colors serves as a warning to
predators that the insect may be distasteful and potentially toxic. Milkweed is
full of a compound called cardenolides. When a caterpillar feeds on milkweed
plants, the cardenolides stay in the body of the monarch, which makes it
distasteful and toxic to predators like birds. The predators learn to stay away
from insects with the bright coloring.
For a long time, scientists suspected viceroy
butterflies mimicked monarchs in a form of Batesian mimicry meaning that the viceroy appeared toxic and
distasteful to predators based on coloring and wing shape, but they were not
actually toxic or distasteful. Further research indicates that the monarch,
viceroy, and queen butterflies may exhibit Müllerian mimicry, meaning all three
can be distasteful or toxic to predators and they mimic each other. More
research is needed to fully understand this mimicry relationship between the
butterflies because variations in the butterfly’s colors, wing shape,
distastefulness, and toxicity vary among different regions and caterpillar host
A viceroy butterfly
can be differentiated from a monarch by the black, circular line through the
hind wing that is perpendicular to the other black veins.
|A queen butterfly has more white spots on the hind wings than a monarch. Colors can be variable but often they are a darker orange color than monarch butterflies. Photos: Lisa Mason
Monarchs and Other Butterflies
You can support monarchs and other butterflies by providing
food, habitat, water, and space in your landscape. Each species of butterfly
has a different caterpillar host plant, for instance, monarchs rely on milkweed
plants for caterpillar food. Black swallowtail caterpillars feed on dill and
fennel. All adult butterflies will visit a variety of other flowers for nectar.
Plant flowers that have different bloom times so you will have flowers all
season. Butterflies need sunny areas and places to shelter from wind and
weather. Planting a variety of trees and shrubs can help provide sheltering
areas. Be mindful of pesticide use because they can harm caterpillars and
for more information on attracting butterflies to your landscape.
For more information on monarch butterflies, visit MonarchJointVenture.org
To learn more about butterflies in Colorado, read this CSU
Co-Horts blog post called The
Fascinating Lives of Butterflies.