By: Brittany Kingston
Danaus plexippus, also known as a Monarch butterfly is probably one of the most popular butterflies. Growing up it was always such an exciting event to find a caterpillar and then watch it grow into a beautiful butterfly. The Monarch butterfly is used a lot in classrooms to teach about life cycles and migration. It is pretty amazing how such a little insect can fly so far and so fast. They can fly across continents and oceans and have even been recorded at flying as many as 130 km a day during migration (Grund). Continue reading the rest of this website to learn more about this fascinating insect.
Domain: Eukarya (DNA contained in the nucleus)
Kingdom: Animilia (Multicellular heterotrophs that are mobile and lack cell walls)
Phylum: Arthropoda (Chitinous exoskeleton, segmented bodies, paired-jointed appendages)
Class: Insecta (Body consist of head, thorax and abdomen, compound eyes, and 3 pairs of legs)
Order: Lepidoptera (complete metamorphosis, proboscis for sucking, and scaly wings)
Family: Deanaidae ("milkweed butterflies")
Genus: Danaus (large-orange colored butterflies with black veins and white spots on wings)
Species: Danaus plexippus (Monarch butterfly, reduced front legs)
It is hard to tell exactly when butterflies evolved but it was somewhere around 48 million years ago (Monarch Watch). It seems as though butterflies probably evolved from moths because they share many of the same characteristics. Butterflies, however, are diurnal meaning they fly during the day and moths are nocturnal meaning they fly at night. Below is a representation of some of Danaus plexippus's closest butterfly relatives.
Danaus plexippus have a wide geographical range. Their range depends on the presence of milkweed plants that they use for breeding. They range from North and South America, to Hawaii and Australia, and recently are establishing themselves in Western Europe. They also live in a variety of biomes. They live in temperate forests and grasslands, in tropical rainforests and savannas and also in the mountains.
Danaus plexippus also follows a seasonal migration pattern like birds. In the spring and summer, Monarch butterflies can be found further north in open meadows and fields where milkweed is present. Then in the fall, millions of monarch butterflies begin their long journey to their overwintering sites. These overwintering sites are located in southern California and central Mexico. The picture to the left shows thousands of Monarch butterflies overwintering. Some butterflies fly as many as 3000 miles to these sites. Many of the overwintering sites for Monarch butterflies are beginning to disappear because of illegal logging. Luckily, steps have been taken by the American and Mexican governments to protect these overwintering sites.
But you may be wondering how do these tiny little creatures find their overwintering sites year after year? This has been debated about a lot and there are basically two theories that researchers have came up with. One theory is that since they fly during the day that the Monarch butterflies use the sun as a compass when traveling to their overwintering sites. This would involve using the angle of the sun with some sort of internal clock to predict which way was south. Another theory is that Monarchs like birds use some sort of magnetic compass to keep them on track. Both ways are still being studied. However, no matter which way they use; they will always find their way to the overwintering sites.
Migrations of the Monarch butterfly are closely watched. In fact there is a very interesting program that allows students of all ages to be a part of the migration. It is called Journey North. Students in the Northern United States and in Canada, design colorful butterflies that are unique to who they are. Then they are sent to students in areas of Mexico where the Monarch butterflies overwinter. They arrive around the time of the Dia de los Muertos or the Day of the Dead, which is the same time that the actual butterflies begin to arrive. According to Mexican legend, these returning butterflies are thought to carry the ancestors' souls and play a role in the Dia de los Muertos celebrations (About the Symbolic Monarch Migration). The students in Mexico then watch over the butterflies until the spring. When the Monarch butterflies begin to head back, the students in Mexico send the butterflies back with messages for the students in the north. This unique project allows students from all over to be a part of this amazing phenomenon.
Touch: Tactile setae are hairs that extend through a butterfly's exoskeleton and are attached to nerve cells. Setae play an important role in helping the butterfly sense the relative position of their body parts. This is especially helpful in flight. Setae is also located on the butterflies antennae and aid in touch and smell.
Taste: Butterflies have chemorecptors scattered across their bodies. Chemoreceptors are a lot like human taste buds. When a chemoreceptor runs into a chemical , it locks it in and sends a signal to the brain. In monarchs, chemoreceptors are located heavily on the antennae. Males release a chemical called pheromones and females can identify this chemical by using chemorecptors. Chemorecptors are also located on the female's legs. These chemoreceptors are used when the female is trying to find the right plant to lay its eggs on.
Sight: Adult butterflies have compound eyes made up of thousands of ommatidia. Each ommatidia collects light and perceives a picture. This allows the butterfly to look forwards, backwards and to the sides all at the same time. They are also able to perceive polarized light. This is also said to maybe aid the Monarch butterfly in migration.
You do not want to eat me!
Even though Danaus plexippus is able to enjoy great meals, they are not a very appetizing meal for other predators. Milkweed plants produce glycosides which are a type of chemical defense that the plants produce to keep away herbivores. When larvae eat the milkweed, they collect and store these glycosides. This causes the Monarch butterfly to taste horrible to its predators. Many other butterflies will actually try to mimic the Monarch butterfly's colors to scare away predators. One good example of this is the Limenitis archippus, also known as the Viceroy butterfly. The pictures below are of both a Viceroy butterfly and a Monarch butterfly. Can you tell which one is which?
The butterfly on the left is the Viceroy butterfly and the one on the right is the Monarch butterfly. Birds flying above can not tell the difference between the two butterflies so they will leave each of them alone. However, the difference between the two can easily be seen in these two pictures. The Viceroy butterfly has a black stripe across its two back wings and the Monarch does not.
Danaus plexippus reproduce early in the spring right before they begin their migration to the north. Monarch butterflies reproduce sexually and fertilization is internal. The courtship of Monarch butterflies is a little different than most Lepidoptera because the males sometimes force the females to copulate with them. Also Danaus plexippus do not depend on the release of pheromones as much as other butterflies. Courtship first begins in the air. The aerial phase consists of the male nudging and eventually tackling the female to the ground. While on the ground, copulation occurs. The male’s spermatophore is transferred to the female. Only about 30% of mating attempts at overwintering sites end in copulation (The Monarch Butterfly, 61). Then once the female reaches the breeding grounds, she lays the eggs on a milkweed plant.
Monarch butterflies also go through complete metamorphosis. Complete metamorphosis has four distinct stages. These stages include: egg, larva, pupa, and adult. The first stage of the life cycle is the egg. Once the egg is laid on the milkweed plant, it takes anywhere from 3 – 15 days to hatch. The egg then hatches into a larva. The larva feeds on the milkweed plant and grows into the caterpillar. The caterpillar is yellow, black and white striped. After about a two week period the caterpillar attaches its self upside down to a twig. Within a period of about two hours, the caterpillar will shed its outer skin and form a chrysalis. About two weeks later, the adult Monarch butterfly will emerge from the chrysalis.
Larva Pupa Adult
Danaus plexippus interact with a variety of species. In the larval stage of Danaus plexippus, the caterpillar uses a milkweed plant as its host plant. The milkweed provides the larva with food and nutrients for it to grow. Monarch butterflies also have some predators. Though most predators are driven away because of the awful taste of Monarch butterflies, some birds, mice, wasps and fire ants still eat them. The Monarch butterfly adult is least likely to be eaten by predators. During overwintering, monarch adults do have some avian predators. It is difficult to tell if the bird is actually a predator or if they are just curious about trying a Monarch butterfly. The egg and larva stage of a monarch butterfly are the most dangerous. Wasps tend to collect larvae to feed to their own larvae. Fire ants also decrease the population of Monarch butterflies in the spring and fall (The Monarch Butterfly, 47). Danaus plexippus is also used as a host. Monarch paraitoids include twelve species of tachinid flies and at least one species of brachonoid wasp (The Monarch Butterfly, 28).
About the Symbolic Monarch Migration (2007). Retrieved April 25, 2007, from http://www.learner.org/jnorth/tm/symbolic/About.html.
An Examination of Monarch Butterfly (Danaus plexippus) Autumn Migration in Coastal Virginia [Electronic version]. (2002). American Midland Naturalist, 147(Vol. 1), 170-174. from Academic Search Premier.
Butterfly Families (n.d.). Retrieved April 22, 2007, from http://imnh.isu.edu/digitalatlas/bio/insects/butrfly/main/btflycld.htm.
Danaus (2006, October 4). Retrieved April 4, 2007, from http://tolweb.org/Danaus_plexippus/76926.
Grzimek, B. (2003). Grzimek's Animal Life Encyclopedia (Vol. 3, 2nd ed.). Detroit: Gale.
Kane, E. (1999). Danaus plexippus (Monarch Butterfly). Retrieved March 27, 2007, from http://animaldiversity.ummz.umich.edu/site/accounts/information/Danaus_plexippus.html.
Monarch Butterfly- Danaus Plexippus (2007). Retrieved March 27, 2007, from http://www.nhptv.org/natureworks/monarch.htm.
Monarch Watch (n.d.). Retrieved April 5, 2007, from http://monarchwatch.org/.
Oberhauser, K. S., & Solensky, M. J. (Eds.). (2004). The Monarch Butterfly: Biology & Conservation. Ithaca, NY: Cornell University Press.
Resh, V. H., & Carde, R. T. (Eds.). (2003). Encyclopedia of Insects. San Diego, CA: Academic Press.
Schappert, P. (2000). A World for Butterflies. Buffalo, NY: Firefly Books, Inc.
Southern Australian Butterflies (2004, August 1). Retrieved April 5, 2007, from http://users.sa.chariot.net.au/~erg/plexippus_ds.htm.
University of Minnesota- Department of Fisheries, Wildlife and Conservation Biology. Research Topics (2006). Retrieved April 6, 2007, from http://www.monarchlab.umn.edu/research/Researchtopics.aspx.
The Monarch Butterfly (2007). Retrieved April 9, 2007, from http://www.kidzone.ws/animals/monarch_butterfly.htm.