Atlas Moth Cocoon

Description:

This is intended to provide some additional information concerning my spotting yesterday - https://www.projectnoah.org/spottings/16.... After the two Attacus atlas moths flew off yesterday evening, just after dark, I thought it might be interesting to take a look at one of the two empty cocoons. So I brought one of them down from the Citrus Tree and took the above photos. I must stress that I have no knowledge of how the metamorphosis inside cocoons works. I just want to describe what I have observed and photographed. Picture #1: shows the complete cocoon. It consists of two leaves, stuck together with the edges curved round to form an enclosure. Inside this enclosure is a kind of bag, or pouch, made entirely of silk threads which have been wound round and stuck together. The whole arrangement is immensely strong and looks to be quite waterproof. The silk threads, which can be seen protruding from the top of this arrangement, act as a tether, tying the pocket and the stems of the leaves to the twig the leaves were growing on. Having pulled on it, to test its strength, I think I can safely say that the silk tether is much stronger than the leaf stem (because I broke the stem easily, but it would have taken brute force to snap the tether). As you can see, the tether is still attached and the leaf stem is broken. Picture #2: The pocket is now free from the leaves and the twig. It took much perseverance to separate these component parts without significant damage. I will now refer to what is in this photo as the "cocoon". Please note that (not yet knowing what is inside) we now have a cocoon consisting of three parts - the tether, the pocket and the section of silk mesh between them. Picture #3: The cocoon is held upright for this picture. At the top of the pocket there is a small hole, around 3 mm in diameter. I immediately thought that I was misunderstanding what I was looking at, how could such a big moth exit through this tiny hole? A little probing with the end of a pair of tweezers gave me the answer. This exit hole or aperture is elastic. It stretches open quite easily and immediately shrinks back to its original size. The next part, is not so certain, but I think the silk mesh, leading to the tether, is probably a suitable material for the moth to cling to when pulling itself up and through the exit hole. The tether, we have already dealt with. Picture #4: As can be seen, I have cut open the pocket to see what, if anything, is inside. Lying beside the open pocket there is the exuvia from the final moult, which has obviously taken place inside. It came out in pieces, but is quite recognizable. Don't forget, the larva had to break out of it as part of the metamorphosis. So it was destroyed during the pupation. When I was cutting open the cocoon, I noticed some pinkish-brown fluid (not much, but enough to be messy). What is this fluid? I have been informed by Francis Floe that it called Meconium and that is a great help, but I still don't know how it works. I will have to do some more research on that. Picture #5: Is just an enlarged view of the exuvia to make it easier to recognise. Picture #6: The cocoon is now cut some more for further inspection. I am so unsure of what I see in this picture that I almost decided to leave it out altogether, rather than risk looking like a complete cretin, but that would be cheating. So, in for a penny, in for a pound. In this picture there is a silk mesh (or net) which seems to act as a kind of floor. It is heavily damaged by my clumsy cutting and probing around, but damage aside, what purpose does it serve. This is where I think I have a plausible idea and the rest of the world thinks I am beyond the pale. This "floor" reminds me of a coffee filter or a tea strainer. So is it there to let the meconium seep down into the bottom of the cocoon, leaving the developing moth high and dry. In other words, is the bottom of the cocoon a sump, intended to hold the excess meconium rather than let it drain out where it might be detected by predators ? Well, there it is. As usual, more questions than answers. One final afterthought; Is it possible that the ancient Egyptians got the idea of Mummification from insect cocoons? After all, they mummified their Pharaohs and other dignitaries, in the belief that they would come back to life. Isn't that an interesting possibility?

Habitat:

The habitat of the Atlas Moth (which created this cocoon and lived inside it for more than five weeks) is a stand of mahogany trees in our back yard, right next to which there is a Citrus tree, also on the Atlas Moth's list of host plants.

Notes:

Wikipedia's article on cocoons is very informative, but I decided to stay away from it and not "dip into it" as I was describing my spotting because then I would be rather like a parrot which just repeats what someone else has said. However, now I can go and read it fully and, hopefully enjoy it. https://en.wikipedia.org/wiki/Pupa#Cocoo.... The following sites give a little information on Meconium: - https://en.wikipedia.org/wiki/Meconium and https://www.reimangardens.com/butterfly/...