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Re: Lemurs and Feathers



On Wed, 20 Jun 2001 21:21:58  
 Jaime A. Headden wrote:
>David Marjanovic (david.marjanovic@gmx.at) wrote, in reply to
>
><Flying insects probably did evolve from swimmers. See Pat
>Shipman: Taking Wing and a Nature paper that I can't find now,
>perhaps I haven't copied it.>
>
JAIME:
>  Irrelevant to vertebrate flight. Arthropods went airborne
>presumably before they went terrestrial, whereas vertebrates
>were terrestrial then went airborne.

I disagree here.  Of course, insect flight may not tell us much about 
vertebrate flight per se, it can be used as a comparison.  I believe in her 
book, Shipman talked about some research by a Penn State team that "discovered" 
that mayflies (or something similar) were poor fliers and seemed to hover on 
water.  This led them to hypothesize that this type of flying did not take much 
energy, and may be a transitional stage in the evolution of insect flight. They 
also hypothesized that aquatic insects developed wings as an extension of their 
gill plates, and after they became large enough these wings could be used to 
hover on the water (not fly, but hover while the body is still touching the 
water-this way less energy is used and a new feeding niche is exploited).  So, 
yes, I do agree that insects started out as aquatic, then became airborne, and 
only then became terrestrial.  Of course, that is assuming that this research 
is correct.  

The evolution of the insect wing and insect flight can tell about the evolution 
of the avian wing.  Why?  I believe another team, which Shipman also mentions 
in her book if I'm recalling correctly, found that the size of insect wings 
determines if they can be used to make the insect an efficient glider.  I 
believe the data stated that the wings had to be more than 20% of the body 
length (or was it mass??) to be efficient gliding mechanisms.  If we compare 
the insect data with the data we can deduce from bird wings, it may help clear 
up the arboreal/cursorial hypotheses that are still heavily debated.  Of 
course, these hypotheses are not the subject of these posts, so I will not go 
into them.  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.  

Steve

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