Tuesday, May 28, 2019

Oak Flat Mine Pond

Before leaving Arizona, Betsy and I visited one of our favorite locations—Oak Flat. This is a nice wildlife area, with a couple ponds and a campground. There is also some mining going on at Oak Flat—in fact, one spot we like a lot is the Oak Flat Mine Pond. We worry that this pond will vanish one day, as a result of the mining operations, but so far it has survived, and always provides lots of odonate activity.

Here's the location of Oak Flat, just a bit north and east of the town of Superior:



The pond is smallish and shallow, with lots of shoreline vegetation. Here's a view of it:



On this trip, we had a nice view of a Roseate Skimmer:



What a beautiful dragonfly. The skimmer was fighting over the perch with a Variegated Meadowhawk, who also thought that this was an ideal perch for surveying the shoreline. Here's the meadowhawk on the same perch, after displacing the skimmer:



They took turns displacing one another.

There were lots of Variegated Meadowhawks at Oak Flat. They really are a prolific species. Here's another one at Oak Flat.



They generally perch above the ground on vegetation, but are comfortable with landing on bare spots on the shore as well. In this view, you can really appreciate the color pattern of the abdomen, as well as the yellow color along the leading edge of the wings.

One final treat from Oak Flat on this visit was a Plateau Dragonlet. We've only seen this species a couple times before, and at only one location—Tortilla Flat—so it was completely unexpected to see one here. Here's a view of the one individual we saw:



Notice the dark head and thorax, in addition to the blue abdomen with a dark tip.

This individual was vying with other insects for perching sites. Take a look at the dragonlet in the following photo:



Do you see two other insects on either side of the dragonlet, perched atop their own stems? The next photo points them out:



In addition, there are a couple of these insects below the dragonlet on the same stem. The dragonfly and these other insects were constantly interacting with one another, though, of course, the dragonfly was always the one to get his way.

Wednesday, April 17, 2019

Arizona Heating Up

Well, the dragonfly activity in Arizona is certainly heating up—as are the temperatures. In fact, the dragonflies are much more active here than they were in Costa Rica a week ago. We went to the Gilbert Water Ranch two days ago and were surprised at all the dragonflies and damselflies that were out to greet us. Here's our odonate list:

Blue-ringed Dancer
Familiar Bluet

Mexican Amberwing
Flame Skimmer
Blue Dasher
Roseate Skimmer

We don't remember seeing the Mexican Amberwing at the water ranch before, so that was a pleasant surprise. Here's a look at one of males we saw:



This small dragonfly looks a bit like a wasp, which may provide it some protection. Notice the dark brownish-red areas on top of the eyes. These are the dorsal fovea, the areas that provide the dragonfly with its best vision.

Just after seeing this dragonfly, we commented on how nice it would be to see the much larger and more brilliantly colored Flame Skimmer. Right on cue, a mature male came in and landed directly in front of us. Here it is:



Shortly after that, we saw this Familiar Bluet, just like the one we saw in Costa Rica:



All in all, a nice day at the water ranch, with lots of dragonflies and damselflies—and this was in addition to the 35 species of birds we saw!

Tuesday, April 16, 2019

Costa Rica: Familiar Friends

We had a delightful time Costa Rica, enjoying the scenery, wildlife, and friendly people. We found a few odonates, and some were rather familiar to us. For example, we ran across this Familiar Bluet on a small pond on a coffee plantation:



As its name suggests, the Familiar Bluet is a common and frequently seen damselfly, especially in Arizona where they are already out in significant numbers.

The next day, we discovered a Carmine Skimmer, which is found in the United States, and is very similar to the Roseate Skimmers we see frequently in Arizona. Here's a picture of the male:



The female was busy laying eggs on some sheet-metal roofing lying on the ground. I guess it was shiny enough, and polarized light enough, to make her think it was water. The male guarded her until she took off for a rest, then he too took time off and perched conveniently for me to take some pictures.

Wednesday, April 10, 2019

Costa Rica: Cerulean Dancer

We just returned from a wonderful trip to Costa Rica. It was a first trip to that country for us, and we explored a number of different areas and habitats. Here's a rough look at our itinerary:



We were there during the dry season, which was great for us, but not as conducive to seeing odonates. Even so, we did see a few. Our first was the Cerulean Dancer, which we saw at a small pond on a tour of a coffee plantation. Here's a look at this attractive damselfly:



Notice its "dancer" habit of holding its wings high above the abdomen when perched. Later we saw a pair laying eggs, with the female partially submerged:



Here's a side view:



It would have been interesting to watch to see if the female would eventually go completely underwater, but we had to get back to join the tour. We only had a few minutes to observe this damselfly, and get a few pictures, but it was fun to see a new species for us in a new country.

Wednesday, March 27, 2019

Dancers in the Desert

A few days ago, Betsy and I visited the Thousand Palms Oasis Preserve in the Coachella Valley, near Palm Springs, California. The temperature was in the mid 80s, and the desert was abloom with a variety of flowers. Here's the view from the valley floor, with Mount San Jacinto in the background.



There were few birds at the oasis on that day, but plenty of damselflies—in particular, dancers. Here's a male California Dancer showing off his beautiful colors:



Notice the typical dancer stance, with wings held high above the abdomen.

We also saw Vivid Dancers there, and here's an example:



Notice the backward pointing black "arrowheads" along the side of the abdomen, and the differently shaped side stripes on the thorax, compared with the California Dancer.

No dragonflies were seen, but it's good to know the vanguard of the odonate population is out in force.

Monday, February 18, 2019

Splash-Dunk/Spin-Dry Analysis for 2011 to 2018

The splash-dunk/spin-dry behavior is an interesting, and previously unreported, aspect of dragonfly behavior. Here's an illustration of the basic features of the behavior:



A dragonfly—often a male Paddle-tailed Darner—plows headfirst into the water (the splash-dunk) a number of times to bathe. When satisfied that it is sufficiently clean, it gains altitude and spins head-over-heels at 1,000 rpm to dry off. This is the spin-dry. The dragonfly spins about a horizontal axis during the spin-dry, like a bicycle wheel, as indicated in the following illustration:



We first started taking data on this behavior in 2011, and since that time we've observed 762 separate splash-dunks events. For each event, we record the number of splash-dunks, which ranges from 1 to 8. The distribution of splash-dunk numbers in an event is shown below:



Notice that roughly 40% of the events consist of a single splash-dunk, many have 2 or 3 splash-dunks, and a couple events have had 8 splash-dunks. The average number of splash-dunks per event is 2.32, which is unchanged to three significant figures over the last three years.

The temporal distribution of splash-dunks has also been stable over the last few years. Here are the results for the number of splash-dunk events seen per month from 2011 to 2018:



The peak of the season is September, which also—not coincidentally—is the peak of the flight season for the Paddle-tailed Darner.

We also keep track of the number of spin-drys seen at the end of an event. Here are the results:



In almost 30% of the events, a spin-dry isn't seen, either because the dragonfly didn't do a spin-dry, or—more likely—because it did a spin-dry out of view. A single spin-dry is seen in about 65% of the events. Sometimes a dragonfly does a spin-dry, and then immediately does another. This is seen in roughly 5% of the events. In addition, a couple events results in 3 spin-drys.

With so many events observed over the last 8 years, the results have become very stable and reproducible from year to year.

Thursday, January 24, 2019

Species Spotlight: Flame Skimmer

Next up in the spotlight is another striking skimmer—the Flame Skimmer. This flame-colored species is quite common in the southwest, but it is also found in Northern California, Oregon, and just recently a sighting was made in Washington, just across the Columbia River from Oregon.

Here's a look at a male Flame Skimmer:



This species is distinguished from the similar Neon Skimmer by having dark-red rectangular "bars" at the base of the wings, near the leading edge. In addition, the coloration in the wings extends beyond the nodus—the bend in the leading edge of the wing—but stops short of the nodus in the Neon Skimmer.

The female of the species is more lightly colored, as seen below:



Notice the "flange" near the tip of the abdomen, which is the female's "egg scoop".

Here are some additional views of the male:





The next photo shows a common practice of this dragonfly—it often perches with its front two legs tucked up behind the head.



Many dragonflies perch this way, and even fly in this configuration.