Avian vs Complete Metamorphosis

Name: Ramesh
Status: student
Grade: nursery
Location: IL

Question: Dear Sir/Madam, I have a 3.5 year old daughter who asked me a question 
for which I am trying to find an answer. We have got her to understand that the 
caterpillar (larva) eats and eats and goes in to pupa (chrysalis) stage before it 
gets transformed into a butterfly. We have also got a picture book that explains 
the process to her. However, when we tell her that little birds break out of their 
egg shell and fly away, she wants to know why she cannot see the "bird caterpillar" 
just as she can see a "butterfly caterpillar"? I know this is a rather complicated 
question to answer in a manner that a 3 year old can understand. However, I wonder 
if you can suggest if there is something analogous to a "butterfly caterpillar". 
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What an interesting story, I'm delighted to hear you are introducing your daughter 
to nature in such a way.
I think you need to make it clear to her that the whole anatomy and life cycle of 
insects is completely different from that of vertebrates, so that she does not 
confuse them. I don't have any references specific to explaining this to very young 
children, these sites may be of some help. Good luck.

http://www.tpwd.state.tx.us/publications/nonpwdpubs/introducing_birds/eggs/

http://42explore.com/eggs.htm

http://www.birdsnways.com/wisdom/ww36eiv.htm

J. Elliott
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Ramesh,

Curious daughters demand a response!  This question can be addressed in very 
complex approaches.  I will assume that you will be the one to discuss this with 
your daughter so I will not be writing this for her age of understanding.

Insects that use complete metamorphosis such as the butterfly rely on the 
caterpillar (larva stage) to feed to provide all the nutrients and energy to grow 
(transform) into the adult while within the chrysalis.  The adult butterfly is 
unable to eat except to acquire moisture and some nectar) sugar from flowers.  The 
sugar is only an energy source.  Most all of the other materials (protein, fats
and nucleic acids) needed to maintain life must be acquired for the adult in the 
caterpillar stage of their existence.  Most adult butterflies are therefore limited 
as to how long they can live as adults; adults exist only for reproduction purposes 
anyway.  The eggs that are laid by the females are simple in structure because of 
her limited resources and can feed immediately and grow as a caterpillar.  I am not 
going to discuss the insects exoskeleton (outside the body skeleton) which dictates 
its small size and limited store abilities.

The Monarch Butterfly is an outstanding exception for it actually migrates to Mexico 
during the winters and can survive for several years.

Avians (birds) do not need a caterpillar stage for the mother provides all the
nutrients in the yolk of the egg for the developing bird to grow directly into an
adult.  The adult bird can also eat and process all nutrients so their is no need 
for a stage to acquire needed nutrients to live and produce nutrient rich egg yolks 
to feed the young.  The young feed after hatching.
They have means of storing materials in their bodies because they can grow to a 
much larger size than insects.  This is an evolutionary function of the internal 
skeleton.  Adult birds can live a great deal longer than a butterfly for these 
same reasons.  This includes surviving winters which requires a great deal of 
energy either in migration or seeking limited food resources in colder climates. 
Birds are larger and can store and function better than the insect which is 
limited by its small size.

I think this will give you what you need for a 3.5 year old.

Steve Sample 
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