Species Spotlight: Variable Darner

Darners are large, conspicuous dragonflies. The species in the spotlight today, the Variable Darner, is even more conspicuous because it has a penchant for landing on vertical surfaces—like fence posts, walls, tree trunks, and people. It is not a particularly common species, however, at least in the northern Puget Sound area. We generally see only a few each year.

The most distinctive field marks for the Variable Darner are the "pinched in" side stripes on the thorax. The stripes are narrower in the middle than at either end, and sometimes "pinch off" entirely to leave a spot at the top and bottom where the side stripe would normally be on other darner species.



The Variable Darner has minimal to nonexistent front stripes on the thorax. In addition, the blue line on top segment 2 of the abdomen is generally incomplete—it starts from the rear of the segment, but only goes about halfway toward the front of the segment.



The tenth segment of the abdomen is cream colored in Variable Darners, and the appendages are simple—that is, they taper smoothly to a point.

Happy Happy Happy-Face!

Over the years I've taken literally thousands of photos of the Happy-face Draongfly (aka, the Paddle-tailed Darner).  Here's a small sampling:

The two photos on the bottom right of the grid were taken on the deck in our backyard.  All of the rest were taken at Cranberry Lake, where we see the Happy-face Dragonfly all the time in the late summer and early fall.

The photo in the center is still my favorite.  In fact, it was the first one I ever took of the Happy-face Dragonfly, on October 22, 2006.  I reached into the bushes with my camera and took a shot of a dragonfly perched there without even looking at the viewfinder.  When I loaded the photo onto my computer at home I was amazed, and I called to Betsy.  "Take a look," I said, "this dragonfly has a happy-face!"  This discovery launched my interest in dragonflies, which has given me great pleasure ever since.

The following quote from Henri Poincaré summarizes my feelings about science and nature quite well.

I might add to this thought, however, that the scientist also delights in nature because it is infinitely intriguing and surprising – just take the Happy-face as an example!

I'm nearing completion of my dragonfly field guide, Common Dragonflies and Damselflies of the Pacific Coast, and one of its features will be spreads on things I've discovered in my days as a dragonflier, like the Happy-face Dragonfly, Splash-Dunk/Spin-Dry, Autumn Meadowhawks egg laying behavior, etc.

Below is the first draft of the left side of a spread on the Happy-face Dragonfly. It provides a view of a variety of Happy-face individuals, showing the variation in their facial features.



On the right side of the spread I compare the Happy-face of the Paddle-tailed Darner with the face of other species of darner. The Shadow and Variable Darners are in the same genus (Aeshna) as the Paddle-tailed Darner, and their faces are quite similar—including eyebrows that are actually pigments on the eyes. On the other hand, the California and Blue-eyed Darners are in a different genus (Rhionaeschna) and their eyes lack the eyebrows, giving them quite a different look.



It's fortunate that my first face picture of a dragonfly's face was of a Paddle-tailed Darner, since it has the most dramatic "Happy-face" look.

Species Spotlight: Variable Darner

The Variable Darner is a large, mosaic darner with a number of distinctive features.  For one, its side stripes are of variable thickness, hence the common name of this species.  The side stripes sometimes even pinch off in the middle.  Similarly, the front stripes of the thorax are small or even absent.  

Another distinctive feature is that the abdomen has cream-colored spots on the 10^th segment.  In addition, the appendages are simple.

The Variable Darner is widespread at small ponds and lakes.  This species tends to perch low to the ground, often on human-made structures with a smooth vertical surface, like a signpost or a wall.  Females oviposit their eggs in logs and other vegetation along the shore.

A Late Darner

This year featured a number of dragonfly species that were flying well beyond their usual flight season. One example of this is the Variable Darner.  We see this species only occasionally at Cranberry Lake, and so it was a particular surprise to see one on October 29, nine days after the previous late flight date.

Here's the flight season of the Variable Darner in our area, including this new extension:

Notice that they start pretty late in the year, and go almost until November.

The next graph shows the Observation Percentage for the Variable Darner – that is, the percentage of all our observations of the Variable Darner that occur in a given month:

Over 60% of our observations occur in August.  As you can see, observations of this species are rather sporadic.

The Variable Darner is widely distributed in North America, as indicated in the following dot map:

Here's its distribution in the Pacific Northwest, which is fairly uniform:

The male Variable Darner that visited up on October 29 is shown below.  Notice the thin side stripes that actually break off into spots, the cream color on the 10th segment of the abdomen, and the simple appendages.

Another characteristic of this species is its propensity for perching on a wall or other flat vertical surface.  In this case it landed on the vertical concrete wall of the dam at one end of Cranberry Lake.  It's very common to see a Variable Darner perched in this way, but the other darners in our area generally land in bushes and trees.

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.