Danaus plexippusmonarch butterfly

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Geographic Range

Danaus plexippus ranges from North and South America and the Caribbean to Australia, New Zealand, the oceanic islands of the Pacific, Mauritius, the Canary Islands of the Atlantic, and, most recently, Western Europe.

Habitat

D. plexippus is a predominantly open country, frost intolerant species whose range of breeding habitats is greatly dependent upon the presence of asclepiad flora (milkweeds). The monarch requires dense tree cover for overwintering, and the majority of the present sites in California are associated with Eucalyptus trees, specifically the blue gum, Eucalyptus globulus. These trees were introduced from Australia and have filled the role of native species that have been been reduced by logging.

Physical Description

Both male and female monarchs are bright orange with black borders and black veins. The veins on the female are thicker than those of the male. Male monarchs also have a swollen pouch on both of their hind wings.

Monarchs are poisonous to vertebrates. Their poison comes from the milkweed they feed on.

Monarchs also use their appearance to ward off predators. Orange is considered a warning color, which will warn predators that monarchs are poisonous, and not to attack them. From a distance, monarchs can blend into their surroundings. Sometimes, their spots will appear to be the eyes of a larger animal, and will ward off predators.

  • Range wingspan
    8.6 to 12.4 cm
    3.39 to 4.88 in

Development

Small caterpillars hatch from eggs laid by female Monarchs. They grow, shedding their skin to get bigger. Eventually each caterpillar stops growing and forms a case around itself called a chrysalis. Inside the chrysalis it changes its body its body in a process called metamorphosis. When it is done it emerges as an adult butterfly.

Reproduction

The mating period occurs in the spring, just prior to migration from the overwintering sites. The courtship of D. plexippus is fairly simple and less dependent on chemical pheromones in comparison with other species in its genus. Courtship is composed of two distinct stages, the aerial phase and the ground phase. During the aerial phase, the male pursues, nudges, and eventually takes down the female. Copulation occurs during the ground phase and involves the transfer of a spermatophore from the male to female. Along with sperm, the spermatophore is thought to provide the female with energy resources that aid her in carrying out reproduction and remigration.

Once they reach their breeding grounds, the females lay their eggs on milkweed host plants. The egg and larval period is temperature dependent and lasts about 2 weeks. At the end of this period, the larva enter a period of pupation, and after 9 to 15 days an adult butterfly emerges.

  • Breeding interval
    Monarch butterflies mate in the spring before they migrate.

Behavior

Like birds, D. plexippus follows a pattern of seasonal migration. There are two distinct populations in the North America, those that breed in the East and those that breed in the West. Each autumn millions of these butterflies leave their breeding grounds and fly to overwintering sites. The Eastern population overwinters in the volcanic mountains of eastern Michoacan in central Mexico. The Western breeders spend their winters along the California coast. Similar migratory behavior has been observed in Costa Rican and Australian populations.

Food Habits

The larva feed on a wide range of milkweeds of the genus Asclepias. From these plants they acquire and store cardiac glycosides, secondary plant compounds that protect them from predation. The adults of the species forage for flower nectar.

Economic Importance for Humans: Positive

Many species of milkweed occurring in parts of the United States and Mexico are known to be poisonous to cattle ,and D. plexippus is considered beneficial because it helps reduce the abundance of these plants. Overwintering sites are of interest to tourists.

Conservation Status

The annual monarch migration is considered a "threatened phenomena" by the International Union for Conservation of Nature and Natural Resources. Steps have been taken by both the United States and Mexican governments along with numerous private individuals and organizations to protect the overwintering sites of these butterflies.

Contributors

Ethan Kane (author), University of Michigan-Ann Arbor.

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

internal fertilization

fertilization takes place within the female's body

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

semelparous

offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

References

Boppre, Michael."The American Monarch: Courtship and Chemical Communication of a Peculiar Danaine Butterfly". pp. 29, 34 in Malcolm and Zalucki (eds.) Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County.

Cockrell, Barbara J., Stephen B. Malcolm, and Lincoln P. Brower. "Time, Temperature, and Latitudinal Constraints on the Annual Recolonization of Eastern North America By the Monarch Butterfly". pp. 234 in Malcolm and Zalucki (eds.) Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County.

Feltwell, John. 1993. The Encyclopedia of Insects. Prentice Hall, New York. Pgs. 111, 143.

Lane, John. "Overwintering Monarch Butterflies in California: Past and Present". pp. 337 in Malcolm and Zalucki (eds.) Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County.

Lynch, Steven P. and Ronald A. Martin. "Milkweed Host Plant Utilization and Cadenolide Sequestration by Monarch Butterflies in Louisiana and Texas". pp. 107-108 in Malcolm and Zalucki (eds.) Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County.

Malcolm, Stephen B. and Myron P. Zalucki. 1993. Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County. Preface, pp. 397-398.

Malcolm, Stephen B. "Conservation of Monarch Butterfly Migration in North America: An Endangered Phenomenon". pp. 358 in Malcolm and Zalucki (eds.) Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County.

Schmidt-Koeing, Klaus. "Orientation of Autumn Migration in the Monarch Butterfly". pp. 282 in Malcolm and Zalucki (eds.) Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County.

Snook, Laura C. "Conservation of the Monarch Butterfly Reserves in Mexico: Focus on the Forest". pp. 364 in Malcolm and Zalucki (eds.) Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County.

Urquhart, Fred A. 1960. The Monarch Butterfly. University of Toronto Press, Toronto. Pg. 35.

Urquhart, Fred A. 1987. The Monarch Butterfly: International Traveler. Nelson-Hall, Chicago. Pgs. XIX, 173-177.

Vane-Wright, Richard I. "The Columbus Hypothesis: An Explanation for the Dramatic 19th Century Range Expansion of the Monarch Butterfly". pp. 183 in Malcolm and Zalucki (eds.) Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County.

Van Hook, T. "Non-Random Mating in Monarch Butterflies Overwintering in Mexico". pp. 49 in Malcolm and Zalucki (eds.) Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County.

Wells, Harrington, Patrick H. Wells, and Steffen H. Rogers. "Is Multiple Mating an Adaptive Feature of Monarch Butterfly Winter Aggregation". pp. 61 in Malcolm and Zalucki (eds.) Biology and Conservation of the Monarch Butterfly. Natural History Museum of Los Angeles County.