Tuesday, December 11, 2012

A Blue Dasher Comes In For A Landing

One of the advantages of being a dragonfly whisperer is that you have a pretty good idea what they're thinking.  In particular, you often know where a dragonfly wants to perch.  As a result, you can take a video of a particular branch or leaf and, before you know it, a dragonfly comes in for a landing.

Here's a case in point.  In the following video, keep a look out for a male Blue Dasher who finds this particular leaf irresistible as a perch.  He enters the frame from the right, rotates to the desired orientation, and then drops down for a landing.  Nice maneuver.

video

Monday, November 26, 2012

The Case Of The Constipated Darner

The story of the Constipated Darner is an interesting one for a number of reasons, not least of which is how it illustrates the deep connection I've developed over the years with the Happy-face Darner (Paddle-tailed Darner).  I first interacted with this dragonfly as a child, when I brought a live one into the house.  More recently, at Cranberry Lake, I discovered its delightful happy-face, and its method of cleaning by splash-dunking into the water and then spin-drying at 1,000 rpm in mid flight.  I've rescued a  number of them that got stuck when they splash-dunked, and have also gotten good at lifting them up from a perch onto my finger for a little visit.  I've even had a Happy-face come to my deck for a house call.  They've brought out the "dragonfly whisperer" within me.

This story begins at Cranberry Lake.  Betsy and I were observing male Happy-face Darners as they flew about the lake searching for mates and interacting with one another.  Suddenly, we saw one begin a series of splash-dunks.  We counted them out as they progressed:  "1, 2, 3, 4, 5, 6, 7, 8".  Wow, eight in a row.  That was a record!  Below is a table of the number of splash-dunks per event versus the number of events for the last two years – including this new observation.  We've seen a total of 265 splash-dunk events, with an average number of 2.31 splash-dunks/event.

Splash-Dunks per Event               Number of Events
1                                                        94
2                                                        65
3                                                        60
4                                                        28
5                                                        13
6                                                        4
7                                                        0
8                                                        1


After completing its 8 splash-dunks, and a nice spin-dry, the darner flew to a cedar tree near the shore to perch.  We could see it clearly, though it was fairly high up.  We noticed something attached to its abdomen, trailing off the back end.  Was something stuck to the darner?  Apparently so.  It was about the length and color of a pine needle.  Did this account for its record number of splash-dunks, as the darner attempted to dislodge whatever this was?  In fact, as we watched, it flexed its abdomen and tried to remove the material by rubbing it against a leaf, but was unsuccessful.

I reached up and grabbed the lowest branch of the cedar tree, and was able to pull down enough to bring the darner closer for better observation.  We saw that it was distressed over this attachment to its abdomen, and that flies were attracted to it.  We began to realize it might be a string of excrement still attached to the unfortunate creature.

At this point I realized that I could now reach up and grab the next higher cedar branch, and bring the darner even closer.  I did so, and got it close enough that I was able to reach up and lift it onto my finger.  Now we could examine it in detail.  Indeed, it had a long string of excrement attached to its abdomen that it was trying to remove.  I took hold of the far end of the string, which was dry and a light tan color, and pulled.  The string separated cleanly from the darner, and it seemed relieved.  I took a few pictures of it on my finger, and then placed it back on a cedar branch where it rested for several more minutes before flying off.

I wonder how the problem developed in the first place?  Or perhaps the better question is: Why doesn't this sort of thing happen more often, given that dragonflies have no fiber in their diet?  Whatever the case, I never imagined my connection with the Happy-face Darner would extend to a situation like this.  I was happy to help, though, and I hope it was able to continue its dragonfly pursuits in a more regular fashion.

Here are a couple photos from this adventure:

The darner perched in the cedar tree with the attachment to its abdomen.  Notice the fly, whose presence is not a coincident.

After pulling the cedar branch down I was able to reach the darner and lift it onto my finger.

So is this why he splash-dunked eight times in a row?  It seems quite likely.

I was able to pull off the attachment and make a clean break.

My friend the Happy-face Darner seemed pleased with the result.

Friday, November 16, 2012

Dragonflies In The Movies: Monster On The Campus

Science fiction movies from the 1950s are a lot of 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 is that it includes a scene that prominently features 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 Cretaceous, 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 a while and the dog reverts to normal.  Only the professor saw the 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 on the coelacanth's flesh and blood – interesting behavior for a dragonfly.  The dragonfly is shooed out the window, where it reverses its evolution until its 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 while.  No CG effects here – just models and wires, which you can probably see in the following photo.



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 – he's now a monster on the campus.

Saturday, November 10, 2012

Happy-Face Makes A House Call

A couple days ago we had a hard rain overnight, but the clouds began to part a bit the next morning.  Betsy went out into the backyard to feed the birds.  A few minutes later she was tapping on my office window.

"Come take a look," she said, pointing toward the deck.

"What is it?" I asked.

"There's a darner perched out here."

"There is? Which one is it?"

"I think it's a Happy-face," she said.

I quickly got up and looked out, and sure enough, there was a Happy-face Darner just outside my office window.  Here are a couple photos.  See if you can spot the darner in the first photo before you look at the next ones.

Our deck after an all night rain.  Can you spot our visitor?

Here's a closer look at our house guest:

The Happy-face Darner rests on one of the posts of our deck.  You can see droplets and small puddles of water from the recent rain.
A closer look at our visitor.  He's an older individual, with worn and tattered wings.  Also, notice the drops of water clinging to his body from the rain.

It was fun to have one of our favorite animals come to visit in our backyard.  We sometimes see a darner patrolling along the cliff during the summer, and I had been pretty sure they were Happy-face Darners, but this was the first time I had seen one perched.

Here's a closer look at this friendly little guy:

There's Mr. Happy-face.  Still smiling, though sitting in the shade and covered with raindrops.

The sun was starting to burn through the clouds, but our friend had perched on the shaded side of the post, and was still covered in raindrops.  He was starting to lose his grip, so I lifted him up and placed him on top of the deck rail.  Here he would get what sun could manage to break through the clouds.  He seems to be enjoying his new perch.

A better place to wait for the sun.

He still has some raindrops on his face, but he's starting to dry out and warm up.  In the next photo you can look deep into his eyes.

Look deep into my eyes.

You can also see the individual ommatidia in his compound eyes.  They are hexagonal close-packed, just like a honeycomb.

The individual eyes of his large compound eye form a honeycomb lattice.

Eventually the sun came out a bit, and he dried off and warmed up.  Here, he's scratching his head, and enjoying the improved day.  Soon he whirled his wings to warm up his flight muscles, then he took off for parts unknown.  Such a fun visit while it lasted.  I'm so lucky to have a visitor like this come right to me as I work in my office!


Toggle back and forth between these last two photos to see him scratching his head.

Tuesday, November 6, 2012

Splashdance

You've heard of Flashdance and splash-dunk.  Well, here's a combination of the two I call splashdance.

In the following video a male darner is chasing another male out of its territory.  Males usually do this by approaching their opponent from below and behind.  They swoop down low, then rise up for the attack.

In this case, however, both dragonflies are speeding along close to the surface of the lake.  As the attacking dragonfly gets closer, the intruder begins to take evasive action.  The attacking dragonfly mirrors these moves, as it continues flying at high speed, but its wing tips hit the surface of the water.  The graceful little dance it does to avoid an unintentional splash-dunk or cartwheel is what I call the splashdance.

video

Monday, November 5, 2012

Intense Interactions And A Split-S Maneuver

The darners at Cranberry Lake are still active on nice days.  Today many were flying over the water, and at one point at least 15 were perched in the bushes.  It was 50 ˚F, calm, with filtered sun.

Both Shadow Darners and Happy-face Darners (Paddle-tailed Darner) were present, but only males were seen.  The interaction between the males seems more intense than in the middle of the season, when females are numerous.  This time of year the males seem desperate to find a female, and as a result are more aggressive with one another.  I also get the impression that sometimes one male grabs another male hoping it might be an andromorphic female.  In any case, the males are grabbing hold of one another this time of year much more than is seen earlier in the year.

Here's a video showing two males that grab one another, spin around, then fall into the water.  They both get out and fly upward.

video


A third male observing the interaction flies upward too, and then does a wonderful aerobatic move where it rolls 180˚ and pitches in the dorsal (positive) direction.  What a nice maneuver.  In aerobatics, this is referred to as a split-s – basically, an Immelmann turn in reverse.

Sunday, November 4, 2012

Splash-Dunk Data For 2011 And 2012

Well, splash-dunking is just about over for this year – though there could be a few more splash-dunks if we get a nice couple days soon.  So far, though, the data for the last two years looks as follows:




In these last two years we've seen 265 splash-dunk events.  Each event consists of 1 to 8 separate splash-dunks, with an average number of splash-dunks per event of 2.31.  The case of 8 splash-dunks, seen just once this year, is an interesting case in its own right.  A later post titled "The Case Of The Constipated Darner" will tell that story in detail.  Here's the link:

http://thedragonflywhisperer.blogspot.com/2012/11/the-case-of-constipated-darner.html

The drop off in the number of splash-dunks in an event is roughly exponential, indicating that splash-dunks are approximately independent of one another.  Roughly speaking, each time a dragonfly dunks there is about a 67% chance it will splash-dunk again.

Most of the splash-dunks were performed by Happy-face Darners (Paddle-tailed Darner).  Here's one of them that was at Cranberry Lake just a few days ago:

A male Happy-face Darner (Paddle-tailed Darner) at Cranberry Lake recently.  What a treat to go to the lake and see these wonderful creatures.

Sunday, October 28, 2012

A Useful Field Mark For Darners: The Dorsal Stripe On Abdominal Segment 2

Field marks are the bread-and-butter of birding and dragonflying.  Having a good suite of field marks for a particular species is important in accurate identification, because a single field mark can be variable or hard to see in a particular situation.

For example, when identifying Hutton's Vireo it's useful to keep in mind a variety of good field marks that distinguish it from the Ruby-crowned Kinglet.  The vireo has light-colored lores, wing bars that lack a dark border, and black feet (as opposed to the yellow feet of the kinglet.)  It's common for only one or two of these field marks to be visible on a given individual as it hops from branch to branch in the bushes, so having a number of field marks to work with can be quite helpful.

With that in mind, a similar situation occurs when identifying certain darners that are quite similar in appearance.  For example, Shadow Darners lack blue spots on the tenth segment of their abdomens (S10), whereas Paddle-tailed Darners (Happy-face Darner) do have blue spots on S10.  The tenth segment of the abdomen isn't always easy to get a look at, and so other field marks are useful, like a strong facial line in the Paddle-tailed Darner that is lacking in the Shadow Darner.

Another field mark that I find to be useful for a number of different darners is the blue stripe that appears on the dorsal surface of S2.  For orientation, the "wasp waist" in male darners is S3, and S2 is the bulbous segment closer to the thorax.  Here is a photo comparison of the dorsal stripe in four different, but similar-looking darners.

A comparison of blue dorsal stripes on four different darner species.  The stripes vary from thin and straight to broad and spindle shaped, to half a stripe, to a stripe that is wider at the base that the top.

The blue dorsal stripe is straight, thin, and fairly uniform in the Paddle-tailed Darner.  In the Shadow darner it is broad and spindle shaped – almost like a chess piece.  Only half a stripe appears on the Variable Darner, and Walker's Darner has a stripe that is wider at the base than at the top.  I need to work more on these to see how consistent they are, and how they can be extended to other species as well.

Here's a gallery of photos showing these darners.  Check out the dorsal stripes as an additional means of identification:

Paddle-tailed Darner (Happy-face Darner).  Note the thin, straight, uniform dorsal stripe on S2.

Again, a nice Paddle-tailed Darner (Happy-face Darner).  You can't see S10 in this photo, but the dorsal stripe on S2 is quite definitive.

A triplet of free-range darners.  From lef to right we have Shadow, Shadow, Paddle-tailed.  These dragonflies were never captured – simply lifted one at a time onto my fingers.  They were free to fly away at any time.

A Shadow Darner shows off his broad dorsal stripe on S2.

Two free-range Shadow Darners.

A Variable Darner sports just half a stripe on S2.

Walker's Darner has a dorsal stripe on S2 that is wider at the base than at the top.

A closer look at the dorsal stripe on S2 for a Walker's Darner.

I've enjoyed using this field mark, and will continue to apply it and test it out for consistency and dependability.

Thursday, October 25, 2012

Sky-Diving Dragonflies

Dragonflies are known for their impressive aerobatic skills.  They can turn on a dime, hover with precision, plow into the water to create a splash-dunk, and even spin-dry at 1,000 rpm in mid flight.  They're amazing flying machines.

A couple days ago, Betsy and I were watching some late-season darners at Cranberry Lake when one made an impressive maneuver and caught a fly right in front of us.  The darner was flying straight and level at about eye level.  It suddenly noticed a fly just above and slightly behind it, and it came to an abrupt stop.  The darner hovered with its body almost vertical, and as it hovered it rotated and repositioned itself slightly so that it was on a direct line with the fly.  Once in position it accelerated and captured the fly in the blink of an eye.  What a display of precision, patience, and power.

All of this is well and good, but did you know that dragonflies can sky dive?  Well, at least that's what I call it.  What they do is bend their abdomen upward, raise their wings up over their body, and then drop briefly in free fall.  They look like a skydiver with arms and legs pointing upward as they plummet toward Earth.  Here are a few photos of a sky-diving darner taken from a slow-motion video:

A darner (probably a male Paddle-tailed Darner) just before doing a sky dive.

The sky dive is beginning, as the darner raises its abdomen.

Now abdomen and wings are raised upward.  At this point the darner drops briefly in free fall.

The same darner is getting ready for a second sky dive.

There goes the abdomen pointing upward.

Now the wings follow the abdomen in pointing upward, and the darner drops downward.

Here the darner is pulling out of his brief free fall.

Here's the video from which these screen captures were taken.

video

So what's going on with sky diving – why are they doing it?  It's hard to know for sure.  At first I wondered if they might be losing altitude quickly, like whiffling geese that sometimes even turn upside down as they drop down to land.  A good link for photos of whiffling geese is the following:

http://clives.shawwebspace.ca/photos/view/whiffling_geese_/

With more observations this explanation seems less and less likely – the darners are able to increase or decrease altitude much more quickly than they do while gliding in free-fall sky diving.

It may be that they are cleaning their wings or abdomen.  Sometimes a perched damselfly will be seen to arch it's abdomen upward – it appears to be rubbing the abdomen against the wings in a cleaning action.  Darners may be doing the same sort of thing, only in mid flight, as they do so many things in their life.  Sky diving isn't very common, so it may be a while before we know more about its purpose.

Friday, October 19, 2012

A Darner In The Bush Is Worth Two In The Hand

A couple days ago there was a brief break in our autumnal rains, and I took advantage of it by zipping up to Cranberry Lake for a few minutes.  It was cool there, 55 ˚F, and breezy – only a bit of sun filtered through the clouds.  Still, five or six darners were flying over the water and checking for females along the shoreline.  In addition, six or seven darners were perched in the bushes, perhaps hoping for a little more sun, and a few Autumn Meadowhawks were perched on the ground.

I decided to do some dragonfly whispering.  I went up to one of the Happy-face Darners (Paddle-tailed Darner) in the bushes and lifted him onto my finger.  Remember that this was a "free-range dragonfly", completely free to take wing at any time.  It had never been caught or manipulated in any way – I simply lifted it up on my finger, which took the place of a branch.  Here's what he looked like as he sat happily on my hand.

A male Happy-face Darner (Paddle-tailed Darner) resting on my hand.  Such a charming fellow.  (The white spots on the eyes are reflections of the Sun.)

Here are a couple more photos of him.  If you toggle back and forth between the photos you'll get an idea of what it looks like as he cocks his head.




After the darner flew off to go about his busy day, I decided to lift another Happy-face Darner onto one finger, and then while he was going along for the ride, lift a Shadow Darner onto a second finger.  This makes for a nice comparison between these two similar species.  Again, remember these are "free-range dragonflies".

A male Happy-face Darner (Paddle-tailed Darner) on the left, and a male Shadow Darner on the right.  The Happy-face has blue on the tenth segment of its abdomen, but the Shadow Darner's tenth segment is black.  In addition, the blue spots are large, and actually get a bit larger, as you go toward the end of the Happy-face abdomen.  In the Shadow Darner, the blue spots get smaller and eventually disappear altogether.

Here's another view.  In this case, notice the top of segment 2 of the abdomen.  For orientation, segment 3 is the one that is narrow – almost like a wasp waist.  Segment 2 is the large, bulbous segment that is closer to the thorax.  On the top of this segment, the dorsal surface, there is a blue stripe in both species.  The blue stripe on the Happy-face Darner is thin and uniform in width.  In contract, the blue dorsal stripe on the Shadow Darner is broad and nonuniform.  It looks a bit like a chess piece, or the profile of a tree.

Happy-face Darner (left) and Shadow Darner (right).  Notice the difference in the blue dorsal stripe on segment 2 of the abdomen.  It is thin and uniform in the Happy-face, broad and nonuniform in the Shadow.

The blue dorsal stripe on segment 2 is a field mark that I haven't seen mentioned in any of the field guides, but I find it quite helpful.  I often see a darner in the bushes, and a leaf blocks a view of the tip of the abdomen.  No worry – if I can see segment 2 I'm in business.

Tuesday, October 16, 2012

We're Off To See The Darner – Walker's Darner

Edmund Murton Walker (1877-1969) was a Canadian entomologist, zoology professor at the University of Toronto, and an assistant director of the Royal Ontario Museum.  His specialty was dragonflies, and it was for him that Walker's Darner was named.

I'm not related to Edmund Walker, as far as I know, but the fact that one of the mosaic darners carries the name Walker has always been a fun connection with my interests.  This is especially true since Walker's Darner is a close relative of the Paddle-tailed Darner (Happy-face Darner), to which I have such a special connection.  Thus, I've long looked forward to seeing a Walker's Darner.

The problem with seeing a Walker's Darner for me is that they had never been seen in Washington.  Their range is mostly restricted to California, with just a few isolated observations in Oregon.  In addition, they don't start flying until mid-summer, when I'm usually in Washington watching Happy-face Darners splash-dunking and spin-drying.

Last week, Betsy and I decided to take a short road trip to enjoy the good weather while it was still with us.  Just minutes before we left I checked OdonataCentral to see if we might be going near any of the observation sites for Walker's Darner in Oregon.  I knew there were a couple sites along the Columbia Gorge, and I thought we might visit one of them – even though it was too late in the season according to some of the field guides.  I was surprised, then, when I saw a new dot on the Walker's Darner map in Washington State, on the Washington shore of the Columbia River!  It was a state record for Walker's Darner, and it was observed just a few weeks before I checked, in the last half of September.  We decided to give the location a try, even though we would be getting there in the second week of October.

OdonataCentral provided details of the location.  It was near White Salmon, on Old Highway 8, about a mile north of the highway on Major Creek Road.  There's a sharp bend in Major Creek Road where a small creek passes underneath, and that's where they were seen.  We arrived there at about 2:00 pm, and just as I was getting out of the car a darner flew by.  We followed its flight until it landed and, sure enough, it was a Walker's Darner.  This was on October 9, 2012, a new late flight date for both Oregon and Washington.

So fun to finally see Walker's Darner, and in Washington to boot, where it had never been seen before.  Below are a couple photos from Major Creek Road.  The darner is perched high in a tree, making photography difficult, but the photos do show everything that's needed for a confirmed sighting.  We've entered our observation with OdonataCentral – it's listed in their records as OC#382101.


Walker's Darner, male, perched high in a tree.  Notice that the side stripes on the thorax are whitish, compared with yellowish stripes on the Paddle-tailed and Shadow Darners.

Walker's Darner.  Notice the paddle-shaped appendages and whitish side stripes on the thorax.  In addition, the tenth segment of the abdomen (S10) is mostly black, but with a light-colored posterior edge.  In the Paddle-tailed Darner, S10 is covered with blue, and in the Shadow Darner S10 is usually completely black.  Notice also the blue dorsal stripe on S2; it is wide at the base and narrow at the top.  In the Paddle-tailed Darner this stripe is uniform and narrow, and in the Shadow Darner it is broad and shaped somewhat like a vase.

Walker's Darner.  A good look at the whitish side stripes on the thorax.

Betsy took a quick picture of me to document the time and place of our first sighting of a Walker's Darner.