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Posts Tagged ‘Monarch caterpillar’

Over the years I have developed the habit of checking milkweed plants carefully whenever I spot them. Milkweed plants host an extensive cast of colorful characters including ladybugs, milkweed beetles, and Monarch butterfly caterpillars (Danaus plexippus). Though I have been keeping an eye out for them for the last couple of months, I was unsuccessful in spotting a Monarch caterpillar until this past Sunday when I finally spotted one at Occoquan Bay National Wildlife Refuge.

This Monarch appears to be in one of its final phases of development as a caterpillar, when fattening up seems to be a priority before forming a chrysalis. It is not surprising, therefore, that most of the edges of the leaves in this photo have been gnawed on by the caterpillar. This caterpillar seems to be a little late calendar-wise in its path to becoming a butterfly, but I did spot several Monarchs yesterday, so it seems that the Monarch migration has not yet taken place, or at least not in its entirety.

 

Monarch caterpillar

© Michael Q. Powell. All rights reserved.

 

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If you ever get invited to dinner by a Monarch caterpillar, you know what will be on the menu—milkweed. Monarch caterpillars consume amazing quantities of milkweed (and nothing else), growing over 2,000 times their original mass during this 14-day phase of their lives, according to Rick Steinau.

Almost everything you read emphasizes that milkweed is toxic to humans (and to animals), but scienceviews.com notes that native peoples all over the United States and southern Canada used milkweed for fiber, food, and medicine. The article warns that milkweed may be toxic “when taken internally without sufficient preparation.” It is especially fascinating to read of the medicinal uses of the plant. It was used to treat backaches and bee stings, to induce postpartum milk flow, and to deal with a variety of stomach problems. The Meskwaki tribe, according to the article cited above, even used milkweed as a contraceptive, that worked by producing temporary sterility.

Milkweed, however, contains cardiac glycosides that are poisonous to humans and livestock, but also may account for its medicinal effect.  Symptoms of poisoning by the cardiac glycosides include dullness, weakness, bloating, inability to stand or walk, high body temperature, rapid and weak pulse, difficulty breathing, dilated pupils, spasms, and coma. (It sounds a lot like being in love!)

I don’t care how well Monarch caterpillars can prepare milkweed, if they invite me over for dinner, I think I’ll probably refrain from eating and just watch them eat (as I did this past weekend). I love Monarch butterflies in all their forms. Nevertheless, I would take my cue from the artist Meat Loaf, who sang, “I would do anything for love, but I won’t do that.”

Monarch caterpillar feeding on milkweed

© Michael Q. Powell. All rights reserved.

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I love examining milkweed plants, because I always find interesting insects there to photograph. Yesterday I spotted a tiny caterpillar on a milkweed leaf that I was pretty sure was a Monarch butterfly-to-be (Danaus plexippus). The colored stripes were very similar to the one whose photo I previously posted, but this one was significantly smaller.

I decided to do some research on the life cycle of the Monarch to try to find out why this caterpillar was so small. The website butterflybushes.com has a wonderful article on the development of the Monarch. I learned that the larva is so small when it hatches that it can barely be seen, but it then consumes its body weight in milkweed leaves daily (Don’t try that at home!). During the 9-14 day larval stage, the caterpillar sheds its skin five times. Obviously this little guy is in a much earlier stage of development than the previous one, who was probably about ready to move to the pupal stage.

Here are a couple of shots of the little Monarch caterpillar that I took with my Canon 100mm macro lens.

Tiny Monarch caterpillar at rest

Tiny Monarch caterpillar eating milkweed

© Michael Q. Powell. All rights reserved.

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The day before I left for my recent trip I managed to get some photos of Monarch caterpillars with my macro lens. It was the first time that I had seen them live. Not surprisingly they were on milkweed plants and seemed to be chomping away with great appetite. I noted too that some of the milkweed plants were full of aphids (and some of them had lots of ladybugs too). I checked a number of sources on-line and they all suggest that the aphids are not directly harmful to the Monarch caterpillars during the two-week stage when they are caterpillars. I looked around today to see if I could see any chrysalis, the next stage of development, or more caterpillars, but found neither. I’ll keep looking!

Monarch caterpillar (click to see more details)

© Michael Q. Powell. All rights reserved.

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