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.