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SPECIES ACCOUNT
MONARCH BUTTERFLY
(Danaus plexippus)
The annual odyssey of the Monarch Butterfly
has long delighted scientists and backyard
naturalists alike. In early spring, these delicate,
diminutive creatures leave their overwintering
site in south-central Mexico and make their way
north - many traveling upwards of 2500 miles,
the females laying eggs as they go. As the
season progresses, typically three generations of
Monarchs, each surviving a month or two, will
eat nectar, pollinate innumerable flowers, and
procreate. The fourth generation will live for as
long as eight months, some individuals making
the entire return trip to back to Mexico over the
course of the fall. This is one of the longest
migrations on earth, rivaling that of baleen
whales. In a constant state of motion, engaged in
a transcontinental, intergenerational relay race
against the seasons, Monarch Butterflies are a
stunning, colorful embodiment of the Earth’s
cyclical changes.
Monarch Butterflies exhibit remarkable
navigational and instinctive abilities. Researchers
have found that they use a circadian clock based
in the antennae, the Earth’s magnetic field, and
the angle of the sun to navigate on their grueling
journey and find the precise overwintering spots
of their ancestors in the mountains of Mexico.
Simply following the coast helps, too! During
the southern migration, many Monarchs in
eastern North America fly southeast until they
reach the Atlantic then follow the coastline for
most of the rest of the trip. That’s partially why
coastal communities
Danaus plexippus atop an Echinacea pallida (purple
coneflower). Monarchs are effective pollinators and
cultivating a variety of native wildflowers is key to
providing suitable habitat for the species. Courtesy Matt
Pelikan/The Nature Conservancy.
receive such heavy Monarch visitation,
especially in the fall. Coastal points like
peninsulas and islands can concentrate vast
numbers of the butterflies (USDA). Monarch
tracking projects including Journey North
(Learner.org) provide graphic representations of
each season’s migration. On Martha’s Vineyard,
Monarchs typically arrive around mid-May
during northern migration, and numbers peak in
late September and early October during their
southern migration. Some northbound Monarchs
choose Martha’s Vineyard as their summer home
(although biologists are still unsure how they
afford it!).
Many theorize that the migration of the
Monarchs, which cannot survive freezing
temperatures and are truly more of a tropical
The Nature Conservancy
Massachusetts Islands Office
18 Helen Avenue, Vineyard Haven, MA 02568
Brian Lawlor,
Program Manager | [email protected] | (508) 693-6287 Ext. 10
species, evolved with the northern expansion of
milkweed, which is both a vital source of food
for the butterflies and the only plant on which
they breed. Milkweeds, which are in the
Apocynaceae family, contain milky latex that is
poisonous to many organisms. The larval
(adolescent) Monarchs are resistant to the
compounds in the latex and are specialized to
ingest large amounts of it, which in turn make
them poisonous or unpalatable to many
predators. Studies suggest that while the
milkweed diet ultimately contributes to a
spectacular defense against predators, sometimes
ingesting the toxic material has negative effects
on the larvae themselves. Often times the high
levels of toxic steroids called cardenolides found
in the latex can cause a temporary paralyzing
effect on the larvae. In other cases, the sticky
latex can render the mandibles of the larvae
immobile, causing them to starve to death
(Zalucki and Brower 1992). Monarchs that make
it to adulthood no longer feed on leaves but
become more generalist eaters, dining on the
nectar of a wide variety of flowering plants.
Several species of milkweed are abundant on
Martha’s Vineyard, which is another reason why
Monarchs are common on the island. However,
like most native plants, milkweed is vulnerable
to habitat destruction and pollution, which are
common occurrences in any area with a
significant human population. Growing
milkweed of several varieties, including
Butterfly Milkweed (Asclepias tuberosa),
Wavyleaf Milkweed (A. amplexicaulis), and
Swamp Milkweed (A. incarnata) can be a great
way to provide a valuable resource for the
butterflies. Several other native Vineyard plants
attract nectaring adult Monarchs as well,
including goldenrods, Indian Hemp, Mottled
Joe-Pye-Weed, and Common Boneset, as well as
various lilacs and asters. Bright-colored flowers
are especially attractive to Monarch Butterflies;
the stunning yellow blooms of Seaside
Goldenrod (Solidago virescens) are a particular
favorite of southbound Monarchs.
Presence of water - even a small amount - will
make your garden all the more hospitable for
insects. Bird baths, ponds, and even simple
puddles can be valuable resources for tired
traveling Monarchs. Native plant buffers can be
a great way to provide suitable habitat for
Monarchs and a host of other insects. Buffers are
strips of a wide variety of native plants and
grasses along the border of a garden or property.
They allow property owners to maintain
biodiversity and native species even if the rest of
the property is not exactly “au naturale.”
Monarch Butterflies can provide your garden
with something very valuable, too! Their
presence can be an indicator of your garden’s
health, and they are wonderful pollinators,
meaning that while they travel from flower to
flower, consuming nectar, they move pollen
from the male anthers of a flower to the female
stigmas of a flower, leading to fertilization. They
are also magnificent reminders of nature’s
beauty, consistency, and resilience.
Migrating Monarchs rest intermittently during their
migration. Shown here is a large swarm roosting on a tree
in Aquinnah in 1973.Courtesy Shirley Mayhew.
Monarchs are easily identified by their large size
(for a butterfly), bright orange color, and bold
black veins on their wings. Males have thinner
black veins on their wings than the females do,
and have small black dots (believed to be scent
scales for attracting females) on each of the
hindwings (National Wildlife Federation). As
distinctive as Monarchs are, it is easy to be
fooled by the Monarch’s lookalike, the Viceroy.
The Viceroy, which mimics the appearance of
the Monarch presumably to trick predators into
thinking that also contains the poisonous
milkweed latex compounds, has a black line
perpendicularly intersecting the rest of the black
wing veins.
Monarchs roost in such great numbers in this photo
taken in Aquinnah in the autumn of 1973 that they
resemble falling leaves. Courtesy Shirley Mayhew.
Martha’s Vineyard, especially Aquinnah and
Chilmark, tend to see great numbers of migrating
and summering Monarchs. During their fall
migration, southbound Monarchs tend to be
funneled by the shape of the Island, often
forming large concentrations near the Gay Head
Cliffs in Aquinnah. West Tisbury’s Shirley
Mayhew has long been an admirer of the
Monarchs and faithfully keeps an eye out for
them every year. Inset are her stunning
photographs of an enormous group of Monarchs
that touched down and roosted on Aquinnah in
1973.