Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Saturday, May 29, 2010

Dragons and Damsels

I love the mythological sounding names we have imposed on these lovely insects - Damselflies and Dragonflies. Identifying these creatures is really the business of specialists, but I have done my best to track down what I was photographing. If anyone has any better suggestions, I would be happy to hear from you.

When I was at Charcoal Tank (West Wyalong district, NSW) last weekend I came across a moist patch of scrub (not wet, actually, but long fresh grass, and bright green shrubs). This was a mere 100 metres from the main dam on the block, but there was no standing water apart from in the dam itself.

Anyway, I was surprised to notice a bunch of Damselflies perched on the leaves of the shrubbery. I took a few images, so you can see what they were.

I am familiar with seeing Damselflies on rushes along the edges of swamps, not on bush shrubbery in dry country, such as West Wyalong. So you can see why I was a bit surprised.
The shrub in question is, I believe, a type of Hop Bush Dodonea viscosa ssp cuneata. This shrub was very common in the eastern end of the Reserve, where the Ironbarks and some Callitris were growing in an open forest spacing, but not amongst the Mallee patches.
This is a male Damselfly,
possibly the Wandering Ringtail Damselfly
Here is the female.
Just nearby to the shrubs which were attracting the Damselflies I saw a brown Dragonfly. I only saw this single specimen, whereas there were many Damsels around this little patch of scrub.I believe this to be a female of the Wandering Percher, If I am correct in that assumption, we are looking at Diplacodes bipunctata. Apparently this is also known as the Common Percher or Red Percher. Certainly it was "perching" when I saw it. (There are several Dragonfly species in which the males are bright red.)

As Dragonflies go, this was a relatively small one, compared to other brown or yellowish Dragonflies I have seen before.

I know that Dragonflies are generally identified by wing markings, and the spacing of their eyes. I did not get a front-on view of this Dragonfly, but it seems to have eyes placed adjacent to eachother (as do most Dragonflies), not widely spaced. Beyond that I cannot say. At least the venation of the wings is fairly clearly visible. Click on this link for a comparison from the Chew Family's website.

An interesting feature of my photo above is that it clearly shows a typical feature of Dragonfly wings, which, in this case is the red-brown panel in the front of each wing, which is called the "pterostigma". This feature is now understood to be aerodynamically important, affecting their ability to glide at high speed. Both Damsels and Dragons have this feature, but it is more clearly visible in the Dragonflies, as they hold their wings open at right angles from their bodies, and they are not overlapped, whereas the Damsels generally fold their wings together, in line with their bodies.

I think of it as being analogous with the little weights which automobile mechanics add to car wheels in order to "balance them". That feature is only important at relatively high speeds, but if your wheels are out of balance, you certainly notice it.

Fancy Dragonflies and Damsels having solved a problem of the aerodynamics of flight in this way. Ain't Nature wonderful?

5 comments:

catmint said...

yes - wonderful, and even more wonderful when you have it explained and named. thanks Denis, cheers, catmint

Denis Wilson said...

Thanks Catmint.
Well, I have tried to "explain" - lets hope I am right.
I seldom see Damselflies, except when visiting swampy areas and visiting people with dams.
Cheers
Denis

Wilma said...

Nice post, Denis. You have some really great shots here! I like the new header photo, too.

Denis Wilson said...

Thanks Wilma
Glad you like the new "Header" image.
Cheers
Denis

Anonymous said...

Very nice pictures, you captured all the details! I'm impressed.