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

[Richard Rowe]

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