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

[Nick and Ailsa Donnelly]

Is it Tyndall or Rayleigh scattering?  

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. 

-----Original Message-----
From: odonata-l-bounces at listhost.ups.edu
[mailto:odonata-l-bounces at listhost.ups.edu] On Behalf Of Richard Rowe
Sent: Thursday, June 21, 2007 7:57 PM
To: Thomas Schultz
Cc: Ode List Serve
Subject: Re: [Odonata-l] color change in female E. geminatum

Thomas Schultz wrote:
> Dear All,
>
> I tried to send this message before but it didn't come back to me so I 
> concluded that it didn't go through.  I apologize if this is redundant.
>
> Has anyone else noticed that females of /Enallagma geminatum/ change 
> their color during copulation?  I am aware of "voluntary" color change 
> in male /Argia apicalis/, but not in any female /Enallagma/.
>
> In the three photos, the top two are of the same tandem before and 
> during copulation.  The lower photo is of a different tandem after 
> copulation.  I have also seen many ovipositing females that have lost 
> their andromorphic coloration.
>
>
> Tom
>
The blue is almost certainly the result of tyndal scattering (it's the right
colour). Hence migration inwards of the scattering particles will change the
shade. Something similar happens in Austrolestes species (there is a Veron
paper from 1973 on this).  In Austrolestes this colour shift is associated
with the thermal environment. Males are dull in the morning until they get
up to temperature, females are dull, but can become brightish blue if they
are in a hot, sunny environment for any length of time (e.g. sometimes when
egg laying).  Your female may be getting cold while she is immobile.

What happened to the two mites on the female's abdomen in the top photograph
(absent in the late wheel photo below,

Richard

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

ph +61 7 47 81 4851
fax +61 7 47 25 1570
JCU has CRICOS Provider Code 00117J 

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