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MONARCH &
VICEROY BUTTERFLIES Dr. E. F. Legner, University of California, Riverside (Contacts) Monarch and
Viceroy Butterflies share a unique quality.
Both of these butterflies have a similar shape, both are almost the
same size, and both have the same colors (Figs. 1 & 2). These butterflies have orange wings with
black veins and white spots on the black wing tips. The big difference is that the viceroys have a narrow black
band across each hind wing (Fig. 2).
This black band is absent from the hind wings of the monarch (Fig.
1). However, to the untrained eye,
the monarch and the viceroy look alike.
Monarch
Viceroy The butterfly, or adult stage, is the only time when these two insects look so much
alike. The larval (or caterpillar)
stage, of the monarch has yellow, black, and white rings around its
body. On the other hand, the viceroy
caterpillar is blotched with green, yellow, and tan. At the pupal stage (or nonmotile stage when internal changes are
occurring), the viceroy chrysalis
(or protective case) is tan and cream colored, but the monarch=s chrysalis is light green with shiny
gold dots. Even the shapes of the two
chrysalises are different. When specialists began studying these
butterflies, they asked questions such as, why are these animals colored
similarly? They decided that the
reason for the similar appearance was that the viceroy had evolved colors
that mimic, or copy, the monarch colors to confuse
predators and thereby protected themselves.
Monarch larvae eat milkweed plants that contain chemicals poisonous to
birds and other predators. Because of
these chemicals, monarchs taste bad when they are eaten by an animal. The animal becomes ill, vomits and learns
to avoid this butterfly or others that look similar. Because viceroys look like monarchs, the
viceroys benefit because the birds learn to avoid them as they do the
monarchs. This kind of mimicry, where
one insect tastes bad (the monarch) and the other tastes good (the viceroy),
is called Batesian Mimicry. It was named after Henry Bates, a 19th
Century English naturalist who first described this phenomenon. Ever since, specialists have looked
further into the viceroy/monarch relationship and realized that this is, in
fact, not an example of Batesian
Mimicry. It was found that the
viceroy butterfly also has a taste that is offensive to the predators. Because both butterflies look alike and
both taste bad, any predators who would have the misfortune of eating either
species learn twice as quickly to avoid either butterfly. This type of mimicry, in which both
similar looking species taste bad, is called Mullerian Mimicry and was named after Fritz Muller who was a 19th
century Brazilian zoologist who first described this phenomenon. MONARCH
BUTTERFLY MIGRATION
Cold weather in autumn and winter is
fatal to most adult insects. Most
butterflies die in autumn and leave their young chrysalises so they can survive the weather extremes in
winter. The monarch butterfly, Danaus plexippus, is an insect that is
unable to survive cold weather in any life stage (larval, pupal, or
adult). In developing mechanisms to
protect itself from the cold winter weather, the monarch has acquired the
ability to migrate. Monarchs spend the winter in the warm
areas of coastal California, or in small, protected land areas in the
mountains of central Mexico. Once the
weather in the north begins to warm and the milkweed plants (the favorite
food of monarch caterpillars) begin to grow, the delicate insects begin their
2,000 mile journey to the north. The migration north from California and
Mexico to Canada, which covers most of the United States, begins around
March. On their way to Canada, the butterflies
stop only to eat flower nectar or to lay eggs on milkweed plants. These larvae hatch in about three days
after the eggs are laid, and in about two weeks the larvae are fully grown. After a larva is about 2 inches long, it
hangs upside down from a branch on some silk strands that are produced by a
spinneret in its mouth. After 24
hours, its skin falls away revealing a light green chrysalis. From 1-3 weeks later, the chrysalis will
open to show a new, brightly colored butterfly. When autumn arrives and the weather
becomes colder, the migration south begins.
This time, the newly-emerged butterflies leave their birthplaces and
travel south where they will spend the winter with millions of other
monarchs. None of the butterflies
that migrated north are alive to lead the migration south, and it is not
understood how the young butterflies find their destination to Mexico. When butterflies reach their southern,
winder destinations, they gather on trees in such large numbers that entire
trees become completely covered with butterflies. The monarch migrations return to these trees year after year. The distance of 2,000 miles is amazing
for any animal, such as birds and butterflies, to migrate. For insects with such small, fragile
bodies, it is even more remarkable.
Be sure this autumn to look outside for monarchs in any life stage in
this process as they are coming back from the north In Riverside, the monarch migration should pass through
sometime in October or November, depending on weather events further
north. (For more information about
monarch butterflies and their migration, contact Julie Ellis at
JELLIS@KUHUB.CC.UKANS.EDU (or c/o O. R. Taylor, Dept. Of Entomology, Univ. Of
Kansas, Lawrence, KS 66045). For
information about helping with the next spring migration, contact Elizabeth
Donnelly at JNORTH@INFORMNS.K12.MN.US (or Journey North, 125 North First St.,
Minneapolis, MN. 55401). INSECTS
FROM THE LAWN
To make the net, your parents or older
brother, sister or friend might help.
An inexpensive insect net can be constructed from a wire coat
hanger. First, bend the hanger into a
square (Fig. 3). The bag for the net
should be made from a fine mesh cloth.
A 5-gallon nylon paint strainer is a good size to sew The net is swung back and forth so that a
flat side is brushing the tops of the blades of grass (Fig. 5). Begin by sweeping for about 30
seconds. Then swing the net swiftly
through the air to force the insects to the bottom. Quickly grab the net about 1/3rd of the way from the bottom to
prevent the insects from escaping.
While a friend holds a clear, self-sealing plastic bag (for example,
ZIPLOC), turn the insect net inside-out into the bag, and shake the insects
into the bag. Once the insects are
inside, seal the bag. After sealing the bag, count the numbers
and kinds of insects. Using your
memory and the guide book, try to identify as many insects as you can. How many different colors of insects can
you count? How do you think an insect=s color might help keep it from being
eaten by other animals? What other
kinds of animals did you catch beside insects? Empty the bag and make another sweeping collection for 30
seconds. Did you catch the same
number of insects? Make several
60-second collections. Did you catch
about twice as many insects in the 60-second collection as you did in the
30-second collections? If you keep a
nature journal, you can record these observations. Do this experiment several times throughout the year and see
how the insects change. When using the sweep net, be careful to
avoid areas where clover or other flowers are to avoid catching bees and
getting stung. References: Arnett, R. H., Jr. & R. L.
Jacques, Jr. 1981 Guide to Insects. Simon An Schuster Publ, N.Y..Entomological
Society of America. 1995. Monarchs and viceroys. Mimicry: the art of disguise. Ent. Soc.
Amer. Newsletter, August 1995. |
