Sunday, October 11, 2015

Four-spot Capture

One of the slow-motion videos I took this summer showed a Four-spotted Skimmer chasing and catching a small fly.  The way he did it was a bit surprising, though.  He waited until the fly passed him, turned and flew ahead of the fly, and then approached it head-on for the capture.  Here are some frames from the video that document the event.

In this frame, we see the small fly (red dot) ahead and to the right of the skimmer.  A blue dotted line goes from the head of the dragonfly to the prey.  The fly is traveling in a straight line at uniform speed – apparently oblivious to the potential danger in its vicinity.

In this frame the dragonfly is basically in its same position, soaring motionless in a headwind, as the fly gets closer.

Here the fly is passing the dragonfly, while the dragonfly continues to hold its position.

As the fly continues on its path, past the position of the soaring predator, the dragonfly suddenly initiates a turn to go toward the potential prey.

Now you might think the dragonfly would overtake its prey from behind and make the capture that way, but instead it zips ahead of the prey and turns to face it, as we see in this frame.

The dragonfly now drops below the prey, and puts itself in a position to rise and capture the prey head-on, which it does just a split second after this frame.

Of course, in real time this happened so quickly that no details could be made out.  I knew a capture had occurred, but that was about all.  Fortunately, the slow-motion video allowed for a detailed look at just how the dragonfly effected its capture.  Cool!

Friday, October 9, 2015

Gray Sanddragon

This April, my sister and her husband joined Betsy and me for a delightful walk around the Boyce Thompson Arboretum, just east of Phoenix, Arizona.  It's a beautiful place, and is particularly good for birding.

One of the stops along the walk is Ayer Lake, shown below:

It's a beautiful spot where we usually see several interesting birds, and an occasional dragonfly.  We often see Flame Skimmers and Blue-eyed Darners here, but this time, quite unexpectedly, we suddenly saw a Gray Sanddragon perched on the shore.  My sister grabbed her camera and took a quick shot, shown below.  It's a good thing she did, because it immediately took off and was never seen again.

We sometimes see this dragonfly at the Arboretum, but until now they had only been seen in Queen Creek, never at the lake.  Thanks to Jennifer's quick camera work, we have documentation of this unusual sighting.

Thursday, October 8, 2015

Longing for the days of Summer

Well, the weather has taken a definite turn toward the cloudy and rainy.  There are still lots of nice Fall days to come, with lots of splash-dunking and spin-drying, but I find myself longing for those bright sunny days of Summer.

Until next year, here's to the memories.

Wednesday, October 7, 2015

Big Man (or Monster) On The Campus

I just happened to see this movie again.  It's a fun example of 1950s sic fi.  I'll repeat this report on the movie in case you missed the original post:

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.

Friday, October 2, 2015

Autumn Has Arrived!

Yes, autumn has arrived – both as reckoned by the calendar, and by nature.

In our backyard, we have lots of Dark-eyed Juncos, which ushered in the Fall season right on schedule on September 23.  The juncos leave our yard at the beginning of Spring – heading for the nearby forests – and return at the beginning of Fall.  They are really incredibly reliable in cueing us in to the changes of the seasons.

Another key indicator of Fall are the Autumn Meadowhawks.  Just a few days ago I had an Autumn Meadowhawk land on my shoulder at Cranberry Lake.  It reminded me of a wonderful dragonfly haiku:

Red dragonfly on my shoulder
calls me his friend.
Autumn has arrived.

In general, if a red dragonfly lands on you – especially in the Fall – you can be pretty sure it's an Autumn Meadowhawk.

Here's a female Autumn Meadowhawk that was seen at Beaver Pond in Winthrop just a few days ago:

She seems to be busy eating something she caught on the wing.  Also, note her yellow legs.  Formerly, this dragonfly was known as the Yellow-legged Meadowhawk, but the legs turn dark with age, and so the name was changed to Autumn Meadowhawk to recognize their late-flying proclivity.

That this individual is a female is clear by the lack of hamules on the underside of the second segment of the abdomen.  This is indicated in the photo below:

You can also see the prominent "egg scoop" near the tip of the abdomen.  The female dips the tip of her abdomen into the water, and collects a droplet of water that is held in place by the scoop – almost like a scoop of ice cream held in place by a cone.  She then lays eggs into the droplet, and finally slams into the shoreline vegetation to dislodge the droplet.  Another view of the egg scoop is shown below:

With Fall in full swing, it's good to see that the orbital changes of the Earth are reflected in the natural world.

Thursday, September 17, 2015

Double Seams

On a recent trip to Magnuson Park in Seattle, I took a few pictures of a young Cardinal Meadowhawk.  When I looked at the photos later it seemed like I was seeing double.  Here's an example of what I mean:

Notice the double images along the abdomen, specifically at the seams between the segments.  I wondered if I had jiggled the camera somehow, or had a smudge on the lens, but the double images were in all the photos.

I had never noticed before that the seams are doubled, but it turns out that it's easier to see the effect in young individuals, when the abdomen is light colored.  The double seams are still present in a mature adult, but they're not as prominent, as can be seen in the following photo:

I decided to check other meadowhawks, and have found that Striped Meadowhawks also have these unusual double seams.  Here's an example:

I haven't found this effect in other meadowhawks yet, like the Autumn Meadowhawk in the next photo.  I'll keep checking, though.

Tuesday, September 15, 2015

Back to School

Well, it's that time of year again – time to head back to school.  Be sure to get everything you need for the new year.  And be sure to be happy!