[Odonata-l] zygopteran appendage shape

[Dennis Paulson]

Hello, odonatists.

Bill Hull and I were just exchanging comments about and photos of  
various damselflies ovipositing in tandem, noticing how some of the  
males rest against the substrate and others are supported more or  
less vertically by the female. Species of Argia oviposit mostly in  
the open, often in current and where there would be nothing for the  
male to grasp. Enallagma much more often oviposit on emergent  
vegetation or floating vegetation in still water where the male can  
rest at water level. I speculate that the larger paraprocts (inferior  
appendages) of Argia could even be an adaptation to better prop the  
male upright in tandem. Enallagma have quite different paraprocts,  
usually pointed and slender rather than bulky and complex as in  
Argia. It seems reasonable that there is some mechanical difference  
in such different appendages. At the same time, in the few species of  
tandem-ovipositing Ischnura, I have not seen any upright males.

It would be interesting to do a survey of tandem-ovipositing  
zygopterans to see how much variation there is in male position and  
if it correlates with appendage type. Lestes have a very different  
hookup, and I have never seen a female supporting a male as you see  
so often in the Coenagrionidae. In fact, I'm not sure I've seen that  
in any other family of zygopterans but Protoneuridae and  
Platycnemididae, in which males are supported much as in Argia. I  
wonder if this is the case in all species of the latter two families.

I don't recall if Philip Corbet discussed this variable in his book,  
and I don't have my copy of it here right now.
-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson at comcast.net



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