Evolution and butterflies: a question

[Theodore James Varno]

> 	I hope you don’t mind my asking an amateur’s question.  A friend 
> of mine and I are having an ongoing discussion about evolution.  His 
> contention is that evolution could not possibly explain the diversity of 
> species, that the leaps which evolution makes are of the “meter” variety, 
> when what is needed is more of the “mile” variety.  

	It might help to think of it this way:  Any insect has two 
general phases of its life - a maturation phase and a reproductive 
phase.  Those qualities which are highly favorable in the maturation 
phase may not at all be favorable in the reproduction phase of the life 
cycle.  An organism that can switch its entire morph between these two 
phases will be at an advantage over those individuals that retain the 
same morph through both (assuming the cost of changing morphs is not too 
high).  

	Caterpillars are eating machines, and can rapidly grow and 
efficiently exploit resources.  Butterflies are much better at dispersing 
and reproducing.  An even better example might be mayflies - many mayfly 
adults don't even have mouths!  They simply eat and grow as larvae, 
metamorphose, and then mate and die as adults in a day or two.  High 
specialization...

	Anyway, to answer your more exact question, molting is a common 
life characteristic in (almost) all insects, and changes during molts, 
over time, can lead to the development of full metamorphosis.  Evolution 
does occur in "meter" steps.  It's important, though, to see the full 
time perspective and to understand that "meter" changes, over millions of 
years, quickly and easily become "miles"...

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 Teddy Varno 
 Duke University		"Twentieth Century, go to sleep."
 tjv at acpub.duke.edu		   - REM
 http://www.duke.edu/~tjv        
 (919) 613-3079			
  					
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