Tuesday, December 25, 2018

Merry Christmas, 2018!

Merry Christmas 2018, and Happy Holidays!

Special greetings from the Happy-face Dragonfly:

To help us all get in the Christmas spirit, here's a physics problem from Walker Physics involving Santa:

The situation can be visualized as follows:

And now for the calculation:

Here's a bit of insight into the results:

Ah, nothing like a physics calculation to add to the enjoyment of a day.

Merry Christmas!

Wednesday, December 12, 2018

Species Spotlight: Fiery-eyed Dancer

Here's a species of damselfly I don't see very often; the Fiery-eyed Dancer. I've seen it at Lake Patagonia in southern Arizona, near the Mexican border, and at the Hassayampa River, near Wickenburg, Arizona.

For a long time those were the only places I encountered this species—and then, unexpectedly, I found one in late May at the Boyce Thompson Arboretum. It may be more common there later in the year, but we're back in the Pacific Northwest then.

In any case, here it is:

Here's a bit closer look:

The bright red on the eyes makes the origin of the name quite obvious, and the identification very easy. In addition, it's clear this is a dancer by the way it holds its wings well above the abdomen.

I hope I get more opportunities to see this striking damselfly.

Monday, December 3, 2018

Late, Late Season Dragonflies

After the last post about late season dragonflies, I wasn't sure if there would be any additional dragonflies to report on this year—especially since the weather turned gray and wet for several days after our last visit. I thought that might signal the end of the dragonfly season once and for all. Well, it turns out they're still flying.

We went up to Little Cranberry Lake yesterday at noon. Nothing. It was overcast and 44 ˚F. We went back home and had lunch. Then around 1 pm the clouds cleared and the sun came out. We returned to the lake and immediately saw an Autumn Meadowhawk sitting on the bench by the dam. It flew around some, and perched in various places. It seems that we only saw one individual, but one is a lot more than zero. I hadn't brought my camera with me, so I don't have a picture of that one. I thought I might have missed my opportunity for a last photo of a dragonfly this year.

This morning we awoke to a heavy frost outside that looked like snow covering the ground. We thought maybe that was it, for sure. Even so, we went back up to the lake at noon. It was sunny and calm, but only 40 ˚F.

At first, we saw no activity. Then I thought I saw one zip by behind me, but I couldn't be sure. Then, a few minutes later, I saw one perched on the dam. I brought the camera with me this time, so I took some pictures. Here's the male Autumn Meadowhawk we saw today:

This one flew around to various different perches, then Betsy saw another one, and I saw yet another one after that, so there were at least a few flying on this sunny, cold day. The Autumn Meadowhawk is a hardy soul!

Saturday, November 17, 2018

Late Dragonflies

Well, it's still dragonfly season!

Yesterday we went to Little Cranberry Lake here in Anacortes. We weren't expecting much, since it had been rainy the last couple days. But the clouds cleared off by mid morning, and at noon it was a nice sunny day, with a temperature of 52 ˚F, so we decided to check out the lake just in case. I'm glad we did.

First, we saw a Tule Bluet, the first damselfly we've seen at the lake since October 9. Here it is:

Next, we saw Autumn Meadowhawks all over the place, with several tandem pairs laying eggs:

They would lay eggs for a bit, in their typical Autumn Meadowhawk way (see my field guide for more details), then they would land on the shore to rest in the sun. Often, this meant that they would land on me, which is always a treat!

Darners were also present—specifically, Shadow Darners. A female was laying eggs on the shoreline for quite some time, and then a male came along and attached to her. He tried to takeoff with her to mate, but she resisted. You can see the male attaching and attempting to takeoff in the pictures below:

Eventually the male gave up, and they separated. The female then landed on the shore to rest:

All in all, quite an active day, especially for so late in the year.

Sunday, November 11, 2018

Cool Dragonflies

Well, we're nearing the end of dragonfly season. The days are getting shorter and colder, but there are still a few dragonflies out there. Yesterday, Betsy and I went to Little Cranberry Lake here in Anacortes to check out the action, and we saw quite a bit. Here's the lakeshore:

The temperature was 44 ˚F the entire time we were there, which was approximately from noon to 1:00 pm.

First, we saw quite a few Autumn Meadowhawks; mostly males, but a few females as well. We didn't see any egg laying activity, however.  Here are a few male Autumn Meadowhawks sitting on the bench near the shore:

This is a great place for them to bask in the sun. On the fence nearby a pair was in the wheel position:

Here are a couple males that at first glance appear to be in tandem, but in fact are just resting in close proximity:

Here's another male resting in the bushes just back from the shore:

We also saw darners, both Paddle-tailed Darners (Mr. Happy Face) and Shadow Darners. Here's a male Paddle-tailed Darner perched in the bushes:

For a size comparison, notice the small housefly at the 10 o'clock position.

Here's a close up of this individual, showing the happy face:

It's always wonderful to see this in person.

Finally, here's a female Shadow Darner:

A close-up look shows a bit of a happy face for her as well:

What a lovely November day at the lake.

Thursday, November 8, 2018

Wingbeat Phasing in Cardinal Meadowhawks

Here's an expanded version of this earlier post. In this new version, I include screenshots showing the various stages of a wingbeat cycle:

Cardinal Meadowhawks lay eggs while the males and females hover in tandem—this is how the male guards "his" female in this species. Here's a photo of a pair of Cardinal Meadowhawks hovering in tandem over an egg-laying site:

They hover for a second or two as the female gets ready to lay one or more eggs. They then dip down and drop off the eggs. The wingbeat frequency during this process is approximately 48 beats per second—that is, five frames at 240 frames per second.

In addition, it's possible to see how the wing beats of the male and female are related to one another. One might think they flap in sync with one another, but that's not the case. Alternatively, one might think they flap independently, but again, this is not the case. What they do is the following:

(1) The female's hindwings flap first.

(2) After 2/5 of a cycle, that is 144˚ of phase later, the female's forewings flap in unison with the
      male's hindwings. This is the key aspect of the hovering flight.

(3) The male's forewings flap 1/5 of a cycle (72˚) later.

(4) Finally, 2/5 of a cycle (144˚) later the female's hindwings flap for the next cycle.

There's a definite relationship between how the male and female flap, it's just not what one might imagine.

Here's a plot that shows the wing positions for both the male and female as a function of time for two cycles:

This same type of phase relationship between the male and female has been seen in Red-veined Meadowhawks and Autumn Meadowhawks. It will be interesting to see how widespread this behavior is among other species.

For a bit more detail, let's take a look at frame-by-frame screenshots for a typical cycle:

Here's frame 1 of the cycle. In this frame, the female's hindwings are up.

Next, frame 2 (recall that the frames are taken at 240 frames per second).

Frame 3 shows the female's forewings and male's hindwings in the up position.

Frame 4 shows the male's forewings up.

Frame 5 ends the cycle.

Frame 6 starts the next cycle, with the female's hindwings up again.

Very interesting phasing between the male and the female.

Monday, November 5, 2018

Species Spotlight: Emma's Dancer

In the spotlight today is a beautifully-colored damselfly—Emma's Dancer. As with other dancers, this damselfly holds its wing above the abdomen when perched. In addition, it has a lovely lavender color on the thorax. Most of the abdomen is also lavender, with a contrasting blue tip.

Here's a male from Lower Crab Creek near Beverly, WA on the Columbia River:

Before finding this species at Lower Crab Creek, we had seen it only a couple times before near Bend, OR; in those cases, however, we generally saw just a single individual. At Crab Creek, they were the most numerous damselfly.

Here's another male, with a bit different lighting showing off the lavender color:

A final male, with even different lighting. It shows the range of colors observed in this species:

We saw lots of females at Crab Creek as well. Here's a male and female in tandem preparing to lay eggs:

Here's a close up of the female. Notice her light brown color, and light stigmas. In addition, the ovipositor is clearly visible at the tip of the abdomen—all damselflies use ovipositors, but many dragonflies use an egg scoop instead, and just drop their eggs in the water.

The next female has her hindwings spread open, and her abdomen bent, as she fends off the advances of a male:

One final look at the female, showing her wings held well above the abdomen:

This is a species that can be locally numerous, but is not particularly widespread.

Monday, October 29, 2018

Aging in the Eight-spotted Skimmer

Dragonflies lead active lives, and as a result, they show clear signs of aging. Here are some photos showing the progression of aging in Eight-spotted Skimmers.

First, we see a fresh, clean young male. Notice the sheen on the sparkling-clean wings, and the nice clean body. Also, we see that the pruinosity (or pluminosity if you like) is not yet fully developed, and the yellow side stripes seen in young males are still visible. A beautiful individual in the prime of its live.

Next, we see a middle-aged individual. The pruinosity is fully developed here, and a dark patch is seen in the middle of the abdomen where pruinosity has been rubbed off by females grasping the abdomen at that location during mating. The wings are nice and brilliant, though not quite as "new" looking as in the previous individual.

Finally, we take a look at an individual that is clearly showing the effects of age. The wings are tattered now, with sections missing here and there. The abdomen is faded, though the dark section in the middle of the abdomen can still be seen.

It's amazing that this individual can still function with wings like that, but it was seen flying about seemingly unaffected by the wear and tear.

Friday, October 26, 2018

Sun Mountain Meadowhawks

A few years ago, Betsy and I spent a few days at the Sun Mountain Lodge in Winthrop, WA to enjoy the wonderful Fall colors. That visit was incredible also because of the six different species of meadowhawks we saw.  Here's our report from October 23 and 24, 2013:

Last week, October 23 and 24, Betsy and I went to the Sun Mountain Lodge in Winthrop, WA to enjoy the Fall colors for a couple days.  It was beautiful there, as you can see in these photos:

Sun Mountain Lodge from our room.
The Fall colors were in full effect.
A Golden-crowned Kinglet gave me an opportunity for a quick snapshot.

We went to the Beaver Pond, of course, but weren't expecting that much dragonfly activity.  We would have been happy to see a few.  As it turned out, the activity was very good, with lots of darners patrolling the shore looking for females, and meadowhawks flying in tandem over the water, dipping and laying eggs.  In some areas, each step would flush several meadowhawks from the ground into the air.  It was delightful.  We had a six meadowhawk day, with the following species:

White-faced Meadowhawk
Striped Meadowhawk
Saffron-winged Meadowhawk
Band-winged Meadowhawk
Black Meadowhawk
Autumn Meadowhawk

A six meadow hawk day would be good in the summer, but was especially pleasant to experience this time of year.  The most common species was the Saffron-winged Meadowhawk.  We saw only one White-faced Meadowhawk, and it set a new record late date by 16 days.  Here are pics of the meadowhawks:

White-faced Meadowhawk.
Striped Meadowhawk.  An older individual with frayed wings and faded stripes.
Saffron-winged Meadowhawk on the left, and Band-winged Meadowhawk on the right.
Black Meadowhawk.  We don't see Black Meadowhawks all that often, so this one was a particular treat.
Autumn Meadowhawk.  One of the "field marks" for Autumn Meadowhawks is that they land on you.

As usual, we had a great time at the Sun Mountain Lodge and the Beaver Pond.