Monday, June 22, 2015

U. S. Open Dragonflies

Last Wednesday, Betsy and I went to the U. S. Open at Chambers Bay.  We logged 6 miles according to Bety's pedometer.  It was worn it, though, because it's quite a course, and the setting is spectacular.  Here's what it looks like at the 18th green.

The view from the 18th green at the U. S. Open at Chambers Bay.

We saw a few golfers we recognized, but also saw some dragonflies.  It turns out there are a couple nice ponds at Chambers Bay, though not on the course itself.  We saw many Blue-eyed Darners flying about, and also several Cardinal Meadowhawks.  During the television coverage we often saw dragonflies zipping across the screen.

Here are some pictures of these dragonflies taken at other locations.  First, the very common Blue-eyed Darner.

A  male Blue-eyed Darner.  Many were seen patrolling the greens of Chambers Bay.

We also saw a number of Cardinal Meadowhawks.

A male Cardinal Meadowhawk.  Notice the intense red color, especially on the abdomen, and the dark red patches at the base of the wings.

Some of the Cardinal Meadowhawks were even flying in tandem, a sure sign that water must by nearby in which they could lay their eggs.

Cardinal Meadowhawks flying in tandem as they lay eggs,

During the tournament, on Saturday, we saw Dustin Johnson getting ready to putt at the 9th green.

Dustin Johnson at the 2015 U. S. Open.

We also noticed a Blue-eyed Darner that was patrolling back and forth near the hole, apparently using it as a landmark to define his territory.  Johnson got ready to putt, but then backed off when he noticed the darner.  His caddy then got out a towel and shooed the darner away.  It was funny, because they both acted like this big "bug" might sting them.  Here's the gentle creature that was causing all the fuss:

A child holding a Blue-eyed Darner.

Dragonflies often have a bad reputation, even though they are quite innocuous – no sting, no bite, and no venom.

In any case, it was fun to watch the U. S. Open on TV and recognize the features we'd seen in person, including the many beautiful dragonflies.

Monday, June 1, 2015

Wing Drooping in Red Saddlebags

The following is an article I've submitted for publication to Argia, the scientific journal of the Dragonfly Society of the Americas.  It reports an interesting type of wing behavior recently observed in red Saddlebags.


Wing Drooping in Red Saddlebags

James S. Walker
Anacortes, Washington

In a recent article (Walker, 2015), I discussed the behavior I refer to as wing whacking.  This type of wing-related behavior was in addition to previously described wing behaviors like wing grabbing (Walker, 2013a), sky diving (Walker, 2013b), and spin-drying (Walker, 2011, 2014).

When I wrote the wing whacking article, I didn’t expect to be reporting on a different modality of wing behavior anytime soon – but I was wrong.  In the last couple months I’ve encountered another type of wing use in which a dragonfly depresses, or “droops,” its hindwings.  The details of “wing drooping,” and its associated behaviors, are the subject of this article.

The Wing Droop

This dragonfly season has been notable in a number of significant ways.  For one, our backyard pond in Mesa, Arizona has played host to two new species this year.  Starting in March, we began to see Red Saddlebags (Tramea onusta) and Red-tailed Pennants (Brachymesia furcata) at our pond.  These new species were in addition to our usual early-season residents, which include Mexican Amberwings (Perithemis intensa), Familiar Bluets (Enallagma civile), and Rambur’s Forktails (Ischnura ramburii).

The Red Saddlebags were of particular interest because they were actively laying eggs, giving many opportunities to observe the detach-and-reattach procedure that is typical of saddlebags.  I was able to obtain several slow-motion videos of their egg-laying behavior, some of which can be viewed on YouTube at the links given at the end of this article.  One video shows a nice example of the typical egg-laying process, while another shows a pair separating so the female can lay eggs, only for her to be intercepted by a second male trying to make off with her as a mate of his own.

I also obtained videos showing pairs of Red Saddlebags gliding serenely in tandem between egg-laying events.  It was in one of these videos that I first observed wing drooping – the second significant development of this dragonfly season.  Once I noticed the drooping, I found that it was happening in virtually all of my videos.  In fact, wing drooping had also occurred – though unnoticed at the time – in videos I took of Black Saddlebags (Tramae lacerata) years ago. 

It’s funny how a new behavior, once properly identified, turns out to have been present and visible all along.  As Sherlock Holmes said in The Hound of the Baskervilles, “The world is full of obvious things, which nobody by any chance ever observes.”  In fact, it turned out that wing drooping was also occurring in still photos I’ve taken of perched Red Saddlebags.  I’ll begin by describing wing drooping in a perched individual, because it’s easier to see the “droop” in that case.

In Figure 1, we see a male Red Saddlebags perched in its normal fashion, near the tip of a twig.  Notice that the plane of the hindwings is more or less parallel to the long axis of the abdomen.


 Figure 1  A male Red Saddlebags perched normally.

In Figure 2, we see the same individual doing a quick wing droop.  In this case, the hindwings are depressed downward below the abdomen, which shows off the saddle patches to good effect.  A moment later the hindwings were returned to their normal position.  The droop and return to normal position is usually completed in a fraction of a second, and can be hard to see in real time – unless you’re looking for it.


 Figure 2  The same male Red Saddlebags “drooping” its hindwings.

Drooping the hindwings like this seems to serve at least a couple different purposes for the dragonfly.  These uses are explored below.

Wing Drooping to Brake

As mentioned earlier, I first noticed wing drooping in a slow-motion video of a pair of Red Saddlebags gliding in tandem.  They were progressing smoothly, slowly gaining altitude in a slight headwind.  Then, suddenly, the male drooped his hindwings, effectively deploying his “air brakes.”  The pair immediately slowed almost to a stop, and descended 10 to 15 centimeters.  The male then returned his hindwings to their “upright and locked position,” and the pair continued flying at a lower altitude.

I decided to digitize the frames of the video over the time span of the wing drooping.  In all, I digitized 120 frames, shot at 240 frames per second, for a total real-time span of 0.5 s.  For each frame I recorded the horizontal and vertical positions of the dragonflies relative to a nearby fixed object.  Figure 3 shows the results, where for clarity I have plotted data points for every fifth frame.  Thus the elapsed time between successive points in Figure 3 is about 0.02 s.


 Figure 3  Position of a pair of Red Saddlebags during the process of wing drooping.

The onset of wing drooping and loss of altitude is clear in Figure 3.  The descent lasts for only about 0.2 s, and hence the whole process is over in the blink of an eye.  Once you know what to look for, however, it can be seen.  The flash of the “saddles” at the start of the descent is particularly easy to spot.  It would be much harder to study this behavior if the saddle patches were not present – perhaps other families of dragonflies are drooping their wings to air brake while in tandem also, but just haven’t been noticed yet because their wings are clear.

It’s not surprising that wing drooping can be used for braking.  This is quite evident from Figure 2, where the Red Saddlebags looks just like an airplane with its flaps lowered.  It turns out, however, that there is at least one other use for wing drooping.  We consider that use next.

Wing Drooping to Signal

After noticing the wing droop in the gliding videos, I looked more carefully at the videos showing the detach-and-reattach egg-laying process.  It turned out the male was wing drooping there as well.

In a typical egg-laying video, a pair hovers over a spot for several seconds – perhaps half a minute or more – before finally deciding to lay eggs at that location.  Careful inspection of the slow-motion videos shows that the male quickly droops his hindwings just before releasing the female.  She then detaches, and the male returns his hindwings to their normal position.  The female descends, dips her abdomen into the water, and rises as the male reattaches.

So far, in all the cases I’ve seen in my videos, the release of the female is immediately preceded by a brief wing droop.  Is the droop a visual signal to the female?  After all, with such large wing patches the droop is a distinctly visible action.  Does it indicate that the male intends to detach?  Alternatively, could the wing droop simply be a side effect of the action necessary for the male to release his grip on the female?  Further study should clarify the matter, but at first glance it appears the male is sending a signal to the female.

Using wing patches as a signaling device is nothing new, of course.  Such behavior is well known in species like the River Jewelwing (Calopteryx aequabilis), for example, where various types of fluttering wing movements are used by the male to show off its wing patches for the benefit of the female (Paulson, 2009).  In the case of the Red Saddlebags the display is very brief, and much harder to see and recognize – at least it’s harder to see with the human eye.

Conclusions

Analysis of slow-motion video shows that wing drooping is a stereotypical motion in which a dragonfly depresses its hindwings.  The drooping can have the effect of an air brake, slowing the dragonfly and decreasing its altitude.  It appears that the drooping can also serve as a signal between the male and female, especially in species with prominent wing patches, as in the case of saddlebags.  Perched individuals also exhibit wing drooping, and in such cases the possibility of a signal to nearby rivals must be entertained.

Acknowledgements

I would like to thank Betsy Walker and Dennis Paulson for helpful discussions and comments.

Literature Cited

Walker, J. S. 2013a.  Attaching in Tandem: The Role of “Wing Grabbing” and “Wing Pulling.”  Argia 25(4): 28-29.

Walker, J. S. 2013b.  Skydiving Dragonflies.  Argia 25(1): 20-21.

Walker, J. S. 2011.  Spin-Dry Dragonflies.  Argia 23(3): 29-31.

Walker, J. S. 2014.  Life at 1,000 RPM.  Argia 26(2): 11-13.

Walker, J. S. 2015.  Wing Whacking.  Argia 27(1): 28-29.

Paulson, D. R. 2009.  Dragonflies and Damselflies of the West, page 42.  Princeton University Press, Princeton, New Jersey.

Online Material

The original, unedited version of this article can be found at the following link:


Red Saddlebags gliding in tandem, and then putting on the air brakes:


Another air brake video:


Normal egg laying in Red Saddlebags:


A second male Red Saddlebags attempts to intercept a female:

Thursday, May 7, 2015

Dragonflies in the Movies: Sci-Fi

Science fiction movies from the 1950s are fun to watch.  They can be so serious in their treatment of a topic, but silly and unintentionally funny, too.

A good case in point is Monster On The Campus from 1958.  It stars Arthur Franz and Joanna Moore, and marks an early appearance by Troy Donahue.  Most interesting from my point of view, however, is that it includes a scene prominently featuring a dragonfly.  But more on that in a moment.  First, here are a couple movie posters for this campy flick:




Hard to resist a movie after seeing posters like that!

Here's the basic premise of the film.  A professor at a small university obtains a coelacanth specimen for his research.  Coelacanths are often referred to as a "living fossils" because they were thought to have gone extinct in the Cretaceous period, until one was found alive and kicking by a fisherman off the coast of South Africa in 1938.  The professor's specimen was preserved by using gamma rays, then sent to his university.  Now we have all the basic ingredients we need for some 50s-style sci-fi – a "living fossil" and radiation.

When the coelacanth is delivered to the professor there is blood is leaking out of its crate, and a dog drinks some of it.  Now, what happens when a dog drinks radiation-treated, living-fossil blood?  Well – naturally – his evolution reverses, devolving him into a "fossil" wolf-like dog.  The effect of the blood wears off after awhile, and the dog reverts to normal.  Only the professor saw the dog's transformation, and without proof no one believes him.

Here's the coelacanth in its crate:


A little later, the professor examines the coelacanth in his lab for a class of students.


Now, here's the key scene:  A dragonfly comes in through the open window and lands on the coelacanth.  The dragonfly now begins to feed on the coelacanth's flesh and blood – interesting behavior for a dragonfly.  The dragonfly is shooed out through the window where, in a matter of minutes, it reverses its evolution until it's a hawk-sized prehistoric dragonfly.  Here it is wanting to get back into the lab for some more coelacanth.


The professor wants to study this "fossil dragonfly", so he lets it back in the lab, where it flies around for a some time.  No CG effects here – just models and wires, as you can probably see in the following photos.



Finally, the professor nets the dragonfly and takes it as a specimen for study.


He doesn't learn that much from the dragonfly, however.  A little later he accidentally gets coelacanth blood on his pipe and smokes it, whereupon he becomes a prehistoric man.  He's no longer a big man on campus – now he's a big monster on campus.

Tuesday, May 5, 2015

Grey Owl

Grey Owl is a delightful 1999 movie by Richard Attenborough, starring Pierce Brosnan as a real-life Canadian trapper turned conservationist, who became a work-wide phenomenon in the period between WWI and WWII.


One of the most enjoyable aspects of the movie is Brosnan's co-star, Annie Galipeau, shown below.  She steals virtually ever scene in which she appears.


The real-life Grey Owl was a great lover of beavers, and firmly opposed to their reckless exploitation.  The beaver shown below with Grey Owl was his friend "Jelly Roll."


At one point in the movie, Grey Owl visits his childhood home in England.  As he explores his old bedroom, we catch a glimpse of an insect collection mounted on the wall, prominently featuring some dragonflies (ah, I finally got around to mentioning dragonflies).


This is a quite enjoyable movie, though little known to the general public.  The role of Grey Owl is certainly a bit of a departure from the roles we normally associate with Pierce Brosnan.

Monday, May 4, 2015

Roseate Skimmer

One of the most common dragonflies at the Gilbert Water Ranch these days is the Roseate Skimmer.  The color of the male shows aptness of the name:

A male Roseate Skimmer resting on its favorite perch.

The female is more cryptically colored, as one would expect.  Here's an example:

A female Roseate Skimmer at the Gilbert Water Ranch.

Notice the large "flange" near the tip of the abdomen.  This is where the eggs come out!

Here's a group of three Roseates, two females and one male, just hanging out near Roseate Bay.  The male is the one at the bottom, lacking a flange.


It's interesting to be able to see so many of these dragonflies of different sex and at different stages of maturation all in one compact location.

Wednesday, April 29, 2015

Rambur's Forktail

One of the first odonates we see each year is the Rambur's Forktail.  In terms of coloration, it is similar to the Western Forktail that is common in Washington – green thorax with a blue tip to the abdomen – but the ranges are quite different.  Notice that the abdomen is black above and yellow below, with a nice straight line demarcating the two colors.  Here's a look at a male Rambur's Forktail:

A male Rambur's Forktail at the Gilbert Water Ranch.  Notice the hamules under segment 2 of the abdomen.

The eyes are similar to those of the Pacific Forktail – black above and greenish-blue below.

Female Rambur's Forktail can look a lot like a male, in which case they are said to be andromorphic (male form).  An example is shown below:

An andromorphic female Rambur's Forktail at the Gilbert Water Ranch.

Notice the flat bottom to segment 2 (S2) of the abdomen.  Thus, this individual lacks hamules, which indicates clearly that it is a female.  In the photo of the male above, the hamules are seen prominently on the bottom of S2.

Females can also look different from the males, and in this case are referred to as heteromorphic (different form).  Here's an example:

Heteromorphic female Rambur's Forktail.

Notice the orange thorax with the black front stripe, and the lack of hamules under S2.  As this individual matures it will become more greenish-brown.

Monday, April 13, 2015

Happy-face On My Finger

I have many pictures of the Happy-face Dragonfly sitting on my finger.  I decided to convert one of them to a drawing.  Notice the paddle-shaped appendages – which are responsible for its official common name, the Paddle-tailed Darner – and the presence of a light-colored spot on the tenth segment of the tail (abdomen).


The official name, Paddle-tailed Darner, isn't particularly apt because a number of different species have paddle-shaped appendages.  For example, the Shadow Darner, Walker's Darner, and the Lance-tipped Darner all have appendages with a similar paddle shape.  This leads to confusion because people often think that paddle-shaped appendages must be distinctive to the Paddle-tailed Darner, and are surprised to find the same shape in other darners.

In addition, the use of "tailed" in the name is unfortunate, because "tail" usually refers to the abdomen, not the appendages.  As an example, the Common Whitetail has a white abdomen (tail); similarly, the Red-tailed Pennant has a red abdomen (tail).  On the other hand, the Brush-tipped Emerald has appendages (tips) that are brush shaped.  So, the Paddle-tailed Darner has a name that is not particularly appropriate – of course, I think it's official name should be the Happy-face Darner!

It's been a long time since I seen one of these guys, much less had one on my finger.  I'm looking forward to becoming reacquainted with them later this year.  In the meantime, here's a YouTube video slideshow of a variety of dragonflies on my fingers:  Slideshow.