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Hyalophora cecropia: A Life Cycle Photo Journal. Part 3: The Cocoon and Pupa.
(reported as it happened) |
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A cocoon appeared a few days earlier than expected. I saw this completed cocoon all wrapped in leaves August 8th. A friend of mine spotting it asked,"what is that thing that looks like a seed pod?" The leaves were then carefully cut or pulled away to allow complete viewing of the cocoon. (spun on August 8th; photo taken August 10th 2009) An attempt is being made, as I post this on August 11th, to photograph another individual cocoon spinning sequence. This is challenging as the caterpillar moves about pulling vegetation together. Much of the spinning becomes hidden from view as new material is interwoven and incorporated into the cocoon thus, partially blocking the larvae from view. Eventually the caterpillar will be completely shrouded in a tough parchment-like two layered cocoon. The process of silk weaving is fascinating to watch. At first, the larvae spends much time covering all surfaces with a layer of silk. Every so often, every 5 to 10 minutes or so while working the outside of the cocoon, it pulls leaves and twigs into close proximity and "glues" them there with strands of silk. In a few hours a rough outline of the future cocoon is discernable. The next several hours, the larva concentrates more on reinforcing the outer coating. Then it will work its way in toward the interior and spin a smaller covering around itself. This is the actual pupation chamber where, hidden from view, it will eclose into a pupa. The entire process will take over a week to complete. |
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Here is a slide show series chronicling the cocoon forming process. The action took about 20 hours from 7pm August 11th until 4pm on the 12th. Click on any thumbnail to view full size images and access a 21 image series.. Use the controls below each picture to advance to the next. |
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| Below is the same cocoon as seen over a month later (Sept, 18,09) as the one shown in the "spinning" slide show above. Notice how the color has become a tan-brown. The silk is tough and resilient. Now the long wait for spring has begun. |
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A video of cocoon construction is shown below. |
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Another cocoon was attached to the side of one of the ten gallon aquariums used for rearing. Note: I had no difficulty rearing cecropias. Placing a sheet of glass over the fish tanks kept in needed humidity. A daily paper towel "diaper" change and an abundant supply of willow leaves is all that was needed. Below the caterpillar can still be seen through the thin outer cocoon covering. Within hours the larvae will be hidden from view. In a few days the color of the freshly spun silk will gradually darken from a "cottton white" to a "coconut brown" as the silk fibers dry, harden and assume a tough "parchment" quality. |
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| Meanwhile, the larvae above has been in its cocoon since August 11th. I have finished photographing other cocoons spinning so have decided to open up this cocoon in an attempt to see the pre-pupal stage. Below is the result. A pair of cuticle scizzers was very helpful for the delicate work of cutting the tough silk cocoon fiber without damaging the fragile insect within. The larvae is now completely helpless. All it can do is wiggle and feebly move about. The eating days are over as it can never eat again. (August 13th 2009) |
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Below: 11:00AM August 20th It was noticed the prepupa was showing bands of brown along the rear abdominal portion. The entire skin was very distended and extremely soft to the touch. light wrinkled areas showed where the old skin was sloughing off. I knew the coming shed was imminent |
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Eclosure to pupae occurred at about 11:30AM this morning. I captured the entire event on camera. Pictures were taken every 15 to 20 seconds. Eclosure itself took about ten minutes. |
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Below you can access a 20 photo sequence showing the the cecropia as it struggles out of the old caterpillar skin to become a pupa. This all happens while protected deep within the cocoon. A cocoon was carefully cut open to allow observation of the prepupa within. |
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As before. Click on a thumbnail photo below to view a full size image. Starting from the left and using the "advance" navigation function under each image will enable you to view them as a slide show of frames showing as it looks every 30 to 40 seconds into the eclose process. |
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Starting at 12:00 noon frames for the pupa "color up" sequence were taken at 20 minute intervals. . After 7PM the interval was lengthened to 45 minutes.. At 12 AM on the 21st, photo intervals were taken at two, six, six and 6 hours apart. ending at 8pm August 21st |
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Once again here is access to another slideshow, this time, showing color change in a pupa as it gradually dries and "firms up" taken 32 hours from 12:00 noon until 8PM the next evening..View the full 24 image show by clicking on a thumbnail. |
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Total time from spinning, prepupa to complete pupae formation was ten days. (The cocoon was made on the 11th.) |
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The same pupa 4 days after eclosure. The brown has deepened but the pupa is still sensitive to being touched. I shall put this cocoon and pupa in a small plastic food preserver to eventually refrigerate and keep in humidity. When the fall weather cools down most whole cocoons will be moved outside for the winter. This should synchronize hatching in late spring with the wild moths. |
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View an event rarely seen by us yet is a common ancient happening in the natural world. Witness what is normally hidden deep within the protection of a cocoon; the transition of a cecropia caterpillar, prepupa to pupa. Then watch as the pupa changes color from jade green to a rich golden brown. To watch click on the "Unshrouded Mystery" video link below. |
| October 7th 2009 I placed all cocoons into a ten gallon tank screened on top and put them outside by my apartment door.The weather is cooling down. Frost is forecast within the week (two weeks early for central Kentucky). Cocoons were covered with a white towel to shield them from morning direct sunlight and prying eyes of neighbors. As the season progresses I plan to put a few into the refrigerator. Hopefully, the low income apt administration and maintenance will not find issue with "bugs" by my front door. I have no garage or other non-climate-controlled area to put them in. |
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To see a monarch butterfly metamorphosis in transition click on one of these links.