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Monarch Butterfly Chrysalis
Danaus plexippus
41.5617, -73.2256
Field Notes
Description:
Just before they pupate, monarch caterpillars spin a silk mat from which they hang upside down by their prolegs (the silk comes from a spinneret on their head). The caterpillar then stabs a stem into the silk pad to hang from. This stem extends from its rear, and is called a cremaster. Once they are in the pupal stage, they will begin their final transformation to become an adult butterfly. Just before the monarch butterfly emerges, their wing pattern becomes visible through the pupal covering. This is not because the pupa is transparent; rather, it is because the pigmentation on the wing scales only develops at the very end of the pupal stage. In the second and third pictures, you can see the wing pattern of the butterfly (but without any of the orange and black colors). This stage of development lasts 8-15 days under normal conditions.
Habitat:
I found this chrysalis on the edge of a rural garden near a meadow and a mixed forest. There were several milkweed plants nearby. The only defense that monarch pupae have against predators is camouflage, and this pupa was hanging in the middle of a rope fence - out in the open, which surprised me because I would have expected to find it in a more protected spot. It was very windy and the chrysalis was being blown about quite a bit, but was so firmly attached to the rope that no harm came to it. It's amazing that something so very fragile can also be so incredibly strong.
Notes:
Monarch metamorphosis from egg to adult takes as little as 25 days, However, it is estimated that fewer than 10% of monarch eggs and caterpillars survive because they are so vulnerable to weather, parasites, and disease. Monarchs are harbingers of environmental change, and it seems that their numbers may be continuing to decline. I have searched 100's of milkweed plants this summer for monarch eggs, caterpillars, and pupae. So far, I have found a total 6 caterpillars, 1 pupa, no eggs, and 4 adult monarchs.
See here for a monarch caterpillar that I spotted in this location last week: http://www.projectnoah.org/spottings/1518454619
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