Chrysalis vs. pupa

[Chris J. Durden]

Bill,
    Exuviae is correct, it is plural because it is often in pieces. It is 
the shed cuticle or outer deposits of the epidermis (skin), and consists 
mostly of chitin and wax.
    I have never heard the eggshell referred to as exuviae. The shed skins 
of both larval stages and pupa are exuviae.
    Think of the individual insect as your letter which is capable of 
maturing a series of "envelopes", much like one of those nested Russian 
dolls. Each envelope is however a little larger than the one before, 
permitting the insect to increase in size within a carefully creased and 
folded exoskeleton. Think also of a tree. The outer bark splits as the tree 
grows, exposing the younger bark beneath.
    Chrysalis and pupa are equivalent, but cocoon is of manufactured silk, 
glued bits of the environment or both, as constructed by the pre-pupal 
larva. Some larvae do this too, like bagworms (psychid moths) and caddis 
flies that construct larval cases.
...................Chris Durden

At 10:20 AM 10/22/2001 -0400, you wrote:
>Just a simple question, maybe I should know the answer but I don't.
>When the last instar of a dragonfly larva climbs up on a rock and
>emerges the exoskeleton it leaves behind has a technical term: Exuivae.
>When a adult butterfly, let's say a Monach, emerges and flies away what
>has it left behind?
>How about a Prometheus moth? What does it leave behind?
>
>It's like a letter. When the postman delivers a letter and you have it
>in hand you say, "Hey I got a letter" holding the object up. But what's
>in your hand is actually a letter AND an envelope. The letter is what's
>inside. We say "letter" for both for convenience.   So it is with
>chrysalis, cocoon, pupa IMHO. There's always a pupa inside, it's the
>envelope that gets a special term.
>                                                                   Bill
>Yule with the same $.02 said a little differently.



 
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