[Odonata-l] Sexual dimorphism question?

[Carlo Utzeri]

Hello Michael,
my hypothesis is that the sexual coloration dimorphism, at least in 
Libellulids, has evolved in the predator-prey context and could be explained 
by the unprofitable prey model: by their colorful apparence, dragonfly males 
signal to (potential) (bird?) predators that it is no convenience to attempt 
to capture them. Dragonflies are in fact very good fliers and are quite able 
to escape capture by most birds. They are active during day hours in open 
habitats, often in full sunlight, and their coloration probably evolved 
bright (aposematic) because it is easier for birds to learn a non-prey item 
by its bright coloration, thus promptly realising that it is not a good job 
of theirs to insist chasing such prey. On the other hand, a dull coloration 
makes females more protected (cryptic) in the shade of woods, where they 
spend most of their time between oviposition bouts.
Greetings
Carlo Utzeri

----- Original Message ----- 
From: "Pilon, Michel" <mipilon at nrcan.gc.ca>
To: <odonata-l at listhost.ups.edu>
Sent: Sunday, February 04, 2007 10:10 PM
Subject: [Odonata-l] Sexual dimorphism question?


> Hello again,
>
> I hope I don't annoy all of you with my naive questions...
>
> After reading the answers about my id's request and considering that in 
> both case the sexual dimorphism is important, I would like to ask you the 
> following question which came to my mind:
>
> What justify that sexual dimorphism amongst dragonflies...?
>
> With birds we know that the female is attracted by the colorful male and 
> that she has to be duller because she has to lay over the eggs and should 
> not be seen by predators...
>
> Is it the same thing amongst Odonata? Does the female attracted by the 
> male colors? And why usually are they duller than the male? (I'm thinking 
> also of Sympetrum obtrusum (white-faced Meadowhawk))
>
> Excuse-me again for my maybe so naive question...
>
> Michel Pilon
> Sherbrooke
> Quebec Canada
>
> Mes Parcours Nature:
> http://parcours.pilonm.org
>
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