I wonder

This is like my educational todo-list about dragonflies. Still very much in the learning, here I'm listing things I wonder about, and would like to know about, but haven't had time to find out about yet. Most of the answers are probably already out there, so it's just a question of finding them. But should it happen that my subject of wonder is not that easily explained, then maybe you'll feel inspired to start wondering yourself, and perhaps find the answers, letting me and the world know about it. Fun.
 
No 1 Saddlebags (Tramea sp.) hiding their frontal legs.
When looking through Dennis Paulson's guides from west and east USA, I came to the tramea species, the magnificent saddlebags, and then I was puzzled by the fact that they only had two pairs of legs! Looking at several photos of different species it looked like they all showed that deviant character. Why? The general structure of the odonates seems to be very similar across species, and it would seem unlikely that just a single tiny lineage of species should have developed out of sync with the others.

And of course it was. When I read the description of the genus it stated that often the saddlebags rest their frontal legs behind the head when perched. And when I looked closer at the photos, it certainly looked like they were there behind the eyes (many photos are unfortunately dark making it difficult to really appreciate details). An unusual behavior since most large dragonflies only do this when they are flying. So my wonder changed from leg number to leg behavior and still stands.

Ok, I looked through my own photos from Denmark, and found that members of the genera Libelula (chasers) and Orthetrum (skimmers) do the same at times. And sometimes with only one leg at a time.

I thought the frontal pair would always be active when catching and eating prey, and that it therefore was logic that the frontal legs could be spared while in a non-eating and resting mode. But then I noticed this photo I have of a male Keeled Skimmer (Orthetrum coerulescens) that is holding and eating a prey item while both legs of the frontal pair are pulled back behind the eyes, and I remain as puzzled as before.
No 2 Salt water not attractive.
Having been around for ages, ancestors dating back to the carboniferous period, some 300 million years ago, these animals certainly have adapted through dramatically changing environments. But assuming that the oceans have been around all their time and water saline also through that time, how come that practically none of the species have adapted to a life cycle depending on salt water pools as environment for larval development, but instead preferring fresh water environments? I know several species can deal with brackish waters, but it is not the same as pure oceanic salinity.
No 3 Aeshna species wintering larvae?
I know that the hawkers seen in Denmark all have a one year cycle going from egg to imago, meaning that the eggs winter and are hatched early in spring whereas the imagos emerge after only a few months in the larva stage. But is it also possible that some larvae hatch late in the season forcing them to winter because there isn't time to complete a full cycle that same year?
No 4 Why doesn't size matter when developing from larva to imago?
How can it be that some large dragonflies can develop from larva to imago in one year, or even the same year, when some smaller damselfly species last several years to develop? I would assume that a larger body mass would require a longer process to mature.
No 5 Late behavior of sympetrum individuals.
Late in the season, October, here in Denmark you see the fully mature individuals of especially Common Darter (Sympetrum striolatum) [Stor Hedelibel] gather where there is sun and no wind. But this often happens away from water, in forest clearings, often sitting on the ground or wood surfaces.
If fully mature I would expect them to be concentrating on finding a mate to complete the reproduction cycle. But they normally just sit there, males and females together without giving much notice to each other.
My instant thought has been that they are individuals that have in fact already ended their reproductive cycle, and now are just relaxing until they die. But then I saw a few mating wheels the other day, end of October, at a pond, and later egg-dropping in the same pond. So, some of them are still active this late in the year, leaving me in doubt now whether they all continue to try to mate until they die, or in fact 'retire' awaiting the grand transition. ??
No 6 Why dragonflies are earlier on the wings than Damselflies in Denmark?
Most of the really early species emerging in Denmark (April) are dragonflies, like Downy Emerald, Four-spotted Chaser, Ruby Whiteface. Except for the Winter Damsel it is only Large Red Damsel that emerge early among the damselflies. Perhaps because they are more dependent on a tall enough ground vegetation to hide in, where the others easily use trees and bushes as protection or to rest in.