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Re: Lemurs and Feathers (well, Arthropods, too!)

On Thu, 21 Jun 2001 19:23:13  
 Jaime A. Headden wrote:
>  I sincerely hope I don't come across as aggravating...


>Steve Brusatte (dinoland@lycos.com) wrote:
><Basically, I could have prevented saying all of the above by
>writing this one statement: insect flight is not related to bird
>flight per se, but studying both the evolution of insect wings
>and how insects utilize those wings can tell us about the
>evolution of the avian wing. Better study is needed, though.>
>  The method in which an insect's wing moves through air is
>different than the manner in which a bird's does. This is
>mechanically related to the size of the wing, and relative size.
>It is also essentially not a birds wing, but a helicopter rotor,
>from what I'm to understand, only sideways and paired (or quad).

I didn't say that it was like a bird's wing.  I said that comparisons may give 
new insights into the reasons for and methods involved with the evolution of 
the avian wing.  

>  That insects went through a "hover" phase is corrolary to
>birds, but the mechanics and origins are distinctly different. A
>vertebrate has different constraints on its design than an
>arthropod does, even a volant one, and these must be considered.
>So while I'm no flight expert, I can see the distinction here is
>to be essentially noted: whether one has ascended from a
>viscuous, thick to diffuse, open environment as water to air, or
>one has remained in an open environment, makes all the
>difference in differentiating how an animal learns to fly.
>Generalizing flyers is not to be done without studying each
>group separate from the others, and not saying "well, in birds
>it did this, so let's see if they did this in arthropods...".
>It's saying "what a unique thing, I wonder what intermediate
>arthropods might elaborate on the evolution of such a structure,
>keeping in mind functional aerodynamics and physics..."

I was not, and am not, generalizing fliers.  I was careful to point out that 
"arthropod flight is not like bird flight per se, but we may be able to gain 
new insights by comparing them." (something like that)  I agree very much with 
most everything you are saying, Jaime.  Birds and insects are definitely not 
one and the same, and the evolution of their wings are incredibly different 
(birds evolved theirs from the arms, insects from gill flaps), as is the 
evolution of their flight (birds either from the ground up or trees down and 
insects from the water up).  However, comparing the two can give interesting 
information and data.  It is not correct in saying that insect flight has 
nothing to do with avian flight.  Both lineages somehow conquered the air, 
modifying structures to exploit a totally new environment.  Of course, the 
structures are not homologous, but definitely analogous.  Birds and insects 
basically did the same thing (evolve flight), so some comparisions can be made!
 although additional study is definitely needed.  


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