[Odonata-l] color change in female E. geminatum

[Richard Rowe]

Nick and Ailsa Donnelly wrote:
> Is it Tyndall or Rayleigh scattering?  
>   
Tyndall is a special case of Rayleigh where the scatterer is about the 
same size as the wavelength of the light being scattered.
> Another way to change the color is to change the refractive index of the
> medium in the cuticle.  Substitute water (liquid) for air and the color of
> scattering should be similarly changed. 
>   
Richard Prum has kindly sent me a copy of his 2004 paper: Richard O. 
Prum, Jeff A. Cole and Rodolfo H. Torres 'Blue integumentary structural 
colours in dragonflies (Odonata) are not produced by incoherent Tyndall 
scattering.' The Journal of Experimental Biology 207: 3999-4009

Which indicates a different mechanism is operating. The scattering is 
not incoherent, scatterers are not independent, and the 1/(lambda^4) 
pattern isn't present.  Nice study!.

Points on migration of scattering particles and the effects of changes 
in the refractive index of the surrounding medium apply.  Room for a 
nice little project for a student interested in structural biology.  I 
suspect migration as methanol fixation tends to retain the blue ...

Richard

-- 
Dr Richard Rowe
Zoology & Tropical Ecology
School of Tropical Biology
James Cook University
Townsville 4811
AUSTRALIA

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