Talk:Monarch butterfly
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[edit] Donated content
(Note: I'm the person who labeled the viceroy (8/24/05), and I have also found several other errors in the written text. I rewrote most of the article, re-organizing it and correcting the errors; however I don't know how and don't feel equal to completing all of the highlighting/double-bracketing that the original article contained, so I have pasted my piece below, hoping that it might be useful. I have left the last two paragraphs untouched. I am connected with the Tyler Arboretum in Media, PA (USA) and they are the source of my information.)
The Monarch Butterfly (Danaus plexippus) is a well-known American butterfly. Its wings feature an easily recognizable orange and black pattern. The females have darker veins on their wings, and the males have a small black spot on a vein in the center of each hindwing (visible in the image to the right) from which pheromones are released.
METAMORPHOSIS The life cycle of the Monarch butterfly includes a change of form called complete metamorphosis, a process that entails four radically different stages and is common to many other insects. The specifics for the Monarch are as follows. First the eggs are laid by females on milkweed leaves. Second, after about 4 days the eggs hatch into tiny worm-like caterpillars. The caterpillars consume their egg cases and then feed on the milkweed leaves whose sap includes a substance called cardenolides, related to glycoside digitalis. This substance is both distasteful and poisonous to Blue jays and other would-be predators, but it is neither distasteful nor harmful to the monarch. The caterpillars eat almost constantly for 9 to 14 days; they grow rapidly, molting several times, until they reach an inch and a half to two inches in length. At this point they stop eating, find a sheltered place (often under a leaf) to attach their hind end with a small silken thread, hang upside down in a “J” position and then molt one final time, becoming encased in an articulated green exoskeleton. This pupa stage is called a chrysalis; during this period the caterpillar undergoes hormonal changes that activate its butterfly genes and suppress its caterpillar genes, thus enabling a complete reorganization from caterpillar to butterfly. After 10 days to 2 weeks the adult butterfly will emerge, able to fly, eat nectar and mate. Most generations will live 2 to 6 weeks. The poisonous cardenolides remain in the chrysalis and the adult, thus maintaining their defense against predation.
Monarch butterflies are brightly colored in order to ward off potential predators, as a signal that they both distasteful and poisonous. This defense works because most predators associate bright colors (especially orange and black or yellow and black) with poison and other unpleasant properties. This phenomenon is called aposematism. This defense is shared by the equally distasteful - and similar-appearing - Viceroy butterfly; it is an example of Mullerian mimicry.
MIGRATION Almost all species of butterflies spend the winter in one of two of their four life stages: either as an egg or as a pupa. Monarchs are, as far as we know, unique in that they over-winter as adult butterflies. Since the adults are much too fragile to tolerate the harsh cold weather of a northern winter they make massive southward migrations in late summer and early fall, and, beginning the following spring, gradually return north over the course of several generations. Thus each migratory round trip takes several generations (one long-lived and several shorter) to complete as follows. Monarchs emerging from their chrysalis from late August through October are members of this migratory generation, forgoing their mating and egg laying until the next spring. Instead they begin their migratory flights toward their over wintering locations: Populations east of the U.S. Rocky Mountains to mountains in Michoachacán, Mexico, and western populations to various sites in central coastal California, notably Pacific Grove and Santa Cruz. How this species manages to complete flights of such great distance and return to the same overwintering locations each year remains a mystery: It is the only migrating flight made by each autumnal generation: None of them has ever done it before. While the life-span of non-migratory adult monarchs is 2-6 weeks, the migratory butterflies live several months, migrating to their wintering grounds, and spend the winter in a kind of torpor (cooled and with greatly reduced metabolic rate). As the days gradually lengthen in early spring the butterflies begin to warm up. They mate and begin to fly north again, though they go only as far as they need to go to find the early milkweed growth; in the case of the eastern butterflies that is commonly southern Texas. As they fly the females keep stopping along the way to lay eggs on the new milkweed, the host plant for the new caterpillars as they hatch. The adults will soon die; the eggs will hatch in four days, the caterpillars will eat and grow for two weeks, will pupate and spend ten days as a chrysalis, and will emerge and live for two to six weeks as adult butterflies, gradually flying northward to take advantage of the northward progression of new milkweed for their egg-laying. Each succeeding generation will follow this life cycle pattern, gradually continuing north along with the milkweed until the end of summer, when once again there will be a migratory generation. (In addition to their normal southerly fall migration, a few east coast Monarchs manage transatlantic crossings, turning up in far southwest Britain in any year when the wind conditions are right.) Much of what we know of the Monarch migrations comes from a program called “Monarch Watch” whose activities include a tagging program (similar to bird banding).
You may want to update this page with the recent discovery on how the butterflies manage to migrate without getting lost. It's quite amazing really. Here's a link to some information: http://www.primidi.com/2005/08/22.html
[edit] What happens to the Monarchs in New Zealand?
The article mentions that they are in New Zealand only in the summertime, but doesn't indicate where they might be the rest of the year. Surely they don't migrate from North America?
No, they overwinter in New Zealand. I wonder if they differ from the U.S. butterflies genetically, or if they are a recently introduced species.
Monarchs make it to Great Britain annually from Mexico, so some may have been blown to New Zealand and started a new overwinter location there, or they may have been transported there by humans.
Monarchs first came to NZ (according to the books) in the mid 1800s. It is understood that in the early 1800s some were blown or flew to Hawaii, later on they arrived in Rarotonga, and finally some got to NZ. They didn't breed here until the early 1900s when someone brought the Swan Plant (Gomphocarpus fruticosus) to NZ.
Here in Russell, Bay of Islands, some overwinter in diapause, while others continue to reproduce all year around.
Check out www.monarch.org.nz for more information.
[edit] Monarch selection of milkweed plants.
Yesterday was in my lower field garden hoeing my beans and saw a caterpillar. Picked it up and placed it on one of several milkweed plants I saved for the butterflies and it rejected it. I pickedc it up several times placing it on the plant and it continued to fall off. I moved it to a different plant and it stayed and started eating the leaves. Why? or How does it select one over the other? 204.96.124.101 22:22, 9 June 2006 (UTC)
This caterpillar may well have been changing from one instar (stage) to another. They usually leave their host plant to do this, to avoid predators, as they are quite still for some time while shedding the skin they've outgrown. It's important not to move them when they're between stages.
Monarchs go through 4-5 instars (the number doesn't change, but it depends what you call the first instar, whether it's 4-5).
[edit] Wanderer Butterfly
I was born and raised in New Zealand and I have never heard of the Monarch butterfly being called Wanderer Butterfly. Just thought I would mention that.
Likewise, I was born and raised here; I remember being told it was also known as the "Greater Wanderer" (perhaps as a US name?) but have only heard it called "Monarch Butterfly" here. Xurizaemon 00:50, 26 August 2006 (UTC)
Monarch is by far the most common name the butterfly is know as in NZ (an impromptu survey of friends and flatmates confirmed this). Maybe Australians call them 'Wandering'? I suggest the wording is changed.
- The google test would seem to back this up - wanderer butterfly "new zealand" - 52,700 hits; monarch butterfly "new zealand" - 178,000 hits. Or if you put the butterfly bit in quotes, wanderer: 604, monarch: 64,000. --Yath 11:45, 26 October 2006 (UTC)
