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Name: Ramesh
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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".


Replies:
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 so their is no need for a stage to acquire needed nutrients to live and produce nutrient rich egg yolks to feed the young. 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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