Monday, August 29, 2005

Apple #102: Monarch Butterflies

Photo from Kidzone

The past few days, I've seen all kinds of Monarch butterflies. Their wings are so freakin' orange it's astonishing. I wondered if they were on their way to wherever it is they migrate to, and the more I looked at them, the more I wanted to know about them. They flitter and flutter in such a haphazard looking way, it's hard to believe that they can all get organized about where to fly to, hundreds of miles away.
  • The Monarch's orange wings signal to predators that they are poisonous. As a larva (caterpillar), it eats only milkweed, and this is what makes the butterfly poisonous.
  • Monarchs spend the winter in warm roosting locales, which are actually in tropical climates and which makes the Monarch a tropical butterfly.
  • No other tropical butterfly migrates as far as the Monarch, which may travel up to 3,000 miles.
  • Monarchs are split into two distinct groups, separated by the Rocky Mountains. The groups look the same and act the same on either side of the mountain range, but as far as anybody can tell, the two groups don't interbreed.
  • In late summer and early fall, the cooler air tells the new Monarch it's time to come out of its pupa, or chrysalid. While other butterflies get to the task of mating at this point, the Monarch does not. Instead, the Monarch feeds to build up fat, which gets stored in its abdomen, and then begins the long journey south.
  • While they travel, the Monarchs continue to eat, scooping nectar out of flowers with their long tongues which they unfurl like a tiny yet very long carpet. They actually gain weight as they travel south. Exactly how they're able to keep flying even though they're getting fatter is a mystery to lepidopterists.
  • During the day, they fly by themselves, but at night they gather in clusters and keep flying. It's dangerous for them to stay in groups in daylight because this makes it easier for predators to snag several at a time.
  • Depending on where they've come from, the Monarchs will fly to very specific places in southern California and Mexico and Florida.

Migration map from Queen's University Dept of Psychology

  • The butterflies will go back to the same area each winter, often roosting in the exact same trees. The puzzling thing is, these are not the same butterflies that made the trip the previous fall. These are actually the great-great-grandchildren of the butterflies who left the roosting places the previous spring. No one knows how the butterflies know where to go to.
  • Some researchers think that Monarchs navigate by using an internal sun compass that compensates for differences in time as they travel. As far as I can tell, this means they navigate according to the position of the sun relative to the equator. How in the world the butterflies know where the equator is, I have no idea.
  • However, just this month, researchers also discovered that butterflies have special photoreceptors in their eyes that detect UV light. These UV receptors are connected to the part of the butterfly's brain that tells it when it's time to start flying. Presumably, these two things working in concert help the butterfly stay on course.

This is a ton of monarchs when they get where they're going.

  • Monarchs are now endangered, and if you "molest a Monarch" in Pacific Grove, California, you may be fined $500.
If you want to see where the Monarchs are now, check here. I don't think this map is inclusive by any means, but as we move into fall, you'll be able to get an idea of where the butterflies have traveled.

P.S. The Daily Apple is getting indexed by more and more search engines! Technorati, a search engine that tracks only blogs, has found us! Click here and scroll down quite a ways.

Monarch Watch, Migration & Tagging
Animal Facts, The Monarch Butterfly
Insecta Inspecta World, Monarch Butterfly
Queen's University, Department of Psychology, Animal Navigation, Monarch Butterflies
"How Butteflies Fly Thousands of Miles Without Getting Lost," News@HebrewU, the Hebrew University of Jerusalem, August 8, 2005
Journey North, Monarch Butterfly, Help track the monarch migration to Mexico

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