Cocoon spinning and pupae pictures of cecropia moths.

Hyalophora cecropia: A Life Cycle Photo Journal.

Part 3: The Cocoon and Pupa.

To return to part 2 the "cecropia caterpillar page click here.

(reported as it happened)

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 larva 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 larva 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 it's 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.

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.

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.

A video of cocoon construction is shown below.

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 larva 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.

Meanwhile, the larva above has been in it's cocoon since August 11th. I 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 larva 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)

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

Eclosure to pupa 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.

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.

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.

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

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.

Total time from spinning, prepupa to complete pupae formation was ten days. (The cocoon was made on the 11th.)

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.

Unshrouded Secrecy: Cecropia Larva, Prepupa To Pupa Transformation from David Britton on Vimeo.

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.

Below are three Cecropia pupae showing individual differences. Two are male and one is a female. Can you tell which one is the female? Remember, males have much larger antennae used for scenting and following pheromones of"calling" females. Females have larger abdomens because of the eggs they must carry.

For a study in contrast:

Below are two pupae photographed December 24th. while in diapause. Both were subjected to local area outside temperatures but were reared as caterpillars in different climates.

The lighter bronze one was reared in New Jersey

while the almost black one experienced a much faster growth period in the hot southern Texas summer of 2010.

South Texas had 90 days of mid 90s to over 100 degree Farenhiet temps. Might this have an impact on pupa color in this native Pennsylvanian cecropia?

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.

It is late Spring!
After nine months in diapause the time for fullfilment and climax of all this
incredible transformation is at hand.

The Date is now May 13th 2010. The weather seems to have warmed up for good. All pupae have been wintered over outside. I have decided to bring them in for close observation and controlled picture taking..

On May 15th I opened up a cocoon to show the the complete interior design with a fully formed pupa within its inner chamber. Here is a cutout view showing the inner structure. The central hard pupal chamber inner-lined with a "mother of pearl" silk bed is cradled and protected by a shroud of silk which is, inturn, enclosed by a tough outer parchment-like outer shell..

The second picture (upper right) is a cutaway ( done May 20th) showing the pupa housed within the pupal chamber. This individual was very dark colored, soft and vulnerable. Moth eclosure from this pupa happened the following day.

Below is the old dried up pupal skin after shedding. Can you find the area where eclosure occured?

Above (right) shows the smooth densely woven interior lining of the pupal chamber housed deep within the cocoon.

Look at the individual differences between the two pupae below. Notice the wing pads and overall color. Even the body width to length is different. Both these pupa are from the same female. Just like in people, brothers and sisters can be uniquely themselves.

Note: Out of five cocoons four are smaller and lighter in color while the fifth, and first to be spun, is darker and "baggier" in appearance. ( Compare the two in the picture below.)

Below are two cocoons that are different shapes and shades of color. The one to the left is a lighter tan while the right one in this picture is a much deeper coconut brown. The darker cocoon also exhibits a "baggier" appearance then the more slender tan cocoon. Both are siblings.

This is a 2nd male pupa taken from its cocoon May 15th 2010. Individual characteristics of shape and color between the two pupae are easily seen.

This pupa is the same individual as seen in the above prepupa to pupa sequence as it is almost nine months later.

This is a specimen I hope to use to show coloration development prior to the moth hatching. This one is a male. Not only are the antennae very large but the genitalia are clearly visible on the lower abdoman. This pupa is beginning to show colors of the adult moth forming within. (May 16th & 20th 2010) In just a few days wing color patterns are becoming more evident.

May 29th an adult moth was seen clinging to its cocoon. Eclosure had happened just a minute or so earlier.

Yet, upon looking later, the cocoon seemed intact. No escape hole was visible. I opened the cocoon to discover a hole at one end of the pupa chamber. It was simply hidden from view by the thick silk surrounding it. I could find little evidence anything had come from inside the outer cocoon casing; certainly nothing as large as this moth yet, two holes are there in the photo; one contained near the bottom on the outer skin peeled away, and the other within the silk on the facing end of the pupal chamber.

      Hopefully, at this point, you have come to appreciate how a hyalophora style cocoon is structured with it's multiiple layers and types of silk spun for different purposes.
      As a study in contrast, here is an example of a much simpler design.
The cocoon below is what an Actias luna moth spins. Lunas utilize a somewhat fragile paper-thin cocoon structure. As is evident in the lower right photo, the pupa is enclosed in a single thin silk layer.
      Unlike the obligatory single brooded cecropia, this species can have anywhere from only one to possibly four generations during a year. The number and timing of flights is dictated by local climate and summer length. One may argue lunas do not need to spin large elaborate cocoons because they only are needed for, perhaps, a month or so during the summer, whereas, cecropias spend close to nine months in pupation. Yet, these relatively simple cocoons also adequately serve lunas in their northern range climates for long periods during harsh winters as well.
     Why do you think these two species of Saturniid moths have come to make such different cocoon structures? How is it that lunas and cecropias have evolved different strategies to cope with similar environmental challenges?
       Perhaps part of the answer may be that over-wintering luna cocoons often fall to the ground with the autumn leaves. They are then buried and protected by forest ground litter and snow during the winter. Cecropia cocoons, on the other hand, remain highly visible as they are strongly attached to small branches. These cocoons are directly exposed to the elements and predation. Cecropia pupae need to be sheltered and protected by their cocoon itself. Thus cocoon design plays a much more critical role.
      This illustrates how two different ways species can adapt and solve similar problems in different ways, each unique strategy allowing individual survival in conditions common to both.

Three luna cocoons seen below as melting snow cover on the forest floor exposes them. Notice how well they blend in. How do their irregular shapes, color and patterns of dead leaves and silk create a camouflage effect? Why is this a succesful survival strategy?

A Cecropia Moth Lifestyle (Pt2)

A Cecropia Lifecycle Complete Metamorphosis Pt2 from David Britton on Vimeo.

Watch in fine detail as a pupa forms inside a cocoon, waits nine months, then emerges the following summer as a beautiful adult moth. Mating ensues followed by a short life of propagation.

Return to part 2 the "cecropia caterpillar page click here.

To see a monarch butterfly metamorphosis in transition click on one of these links. "Egg" "Caterpillar" "Chrysalis" "adult butterfly" . HOME