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MONARCH & VICEROY
Dr. E. F. Legner, University of California, Riverside
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.
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
Home lawns and school yards are homes to many insects. Thy may be collected by a process known as sweeping. Sweeping for insects involves swinging an insect net back and forth almost like sweeping with a broom.
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 onto the hanger as a net. Paint strainers are available at most paint stores for about $1.20 each. The wire hanger can be connected to a broom handle or wooden dowel with duct tape (Fig. 4). Wooden dowels, 5/8 X 36 inches are available at most home supply stores for less than $1.00. You can have fun trying to use an insect field guide to identify the insects you find. An easily understood guide is Simon & Schuster=s, Guide to Insects, by Ross H. Arnett, Jr. and Richard L. Jacques, Jr..
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.
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.