Dragonfly and focus

One of the challenges of insect photography is depth of field. The focal plane of any camera is flat. Insects are three dimensional. To represent a three-dimensional object in two dimensions requires considerable ingenuity on the part of a lens designer, and considerable work on the part of the photographer. One solution is to take multiple images and stack them, focusing on different parts of the insect in each frame. Here's an example of a Blue Dasher, where I was able to get two images with sufficient alignment and sufficiently different focal areas that the resulting image gets most of the bug in sharp focus. Unfortunately, I didn't get a midrange focus, so the tail of the creature is sharp, as are the eyes, but there's an area of soft focus halfway down the back:
Blue Dasher (Pachydiplax longipennis). Boca Raton, FL, October 9, 2016

Blue Dasher (Pachydiplax longipennis). Boca Raton, FL, October 9, 2016. Put your cursor over the image (or click here) to see the labels.

Still, it's a much better image than a single-frame capture would allow. I use a many-years-old version of Photoshop (CS4), but I imagine the process is similar in almost any photo-processing software. Step one: take a few pictures at different focus points:
Blue Dasher (Pachydiplax longipennis). Boca Raton, FL, October 9, 2016

Blue Dasher (Pachydiplax longipennis). Focus is on the head. Boca Raton, FL, October 9, 2016. Put your cursor over the image (or click here) to see the labels.

Blue Dasher (Pachydiplax longipennis). Boca Raton, FL, October 9, 2016

Blue Dasher (Pachydiplax longipennis). Boca Raton, FL, October 9, 2016. Focus is on the tail. Put your cursor over the image (or click here) to see the labels.

Step two: align the images. In Photoshop, this is done by copy-pasting one image onto the other, selecting both layers, then choosing Edit-->Auto-align layers. As long as the previous step (the shooting of the images in the field) was a success, the images should be fairly roughly aligned already. In this case, the software can align them pretty well. I haven't yet figured out how to rescue a poorly aligned set of images, but it might be possible to place them manually with good precision. Step three: stack the images. In Photoshop, choose Edit-->Auto-blend layers. Here again, as long as your previous step (the auto-align) was reasonably successful, the stack will be as well. Of course, if your subject has moved slightly, turning its head or shifting a wing, the resulting stacked image will have "ghosts" in it and will have to be discarded. Step four: save as one image (not a layered file), then you can adjust the colors and highlights, etc., as you normally would. (If you're clever, you might have adjusted the images before aligning and stacking, but I'm rarely that clever. Plus, if you have 5 or 6 images to blend, that's a lot of processing that I'd prefer to do in one step on the final, stacked image.) And that's "all" there is to it!

Here there be dragons

Wow, a record for me. Three days in a row at the Yamato Scrub! My older son, Eric, surprised me midmorning on Labor Day by suggesting that we go to Yamato Scrub. I seized on the suggestion, and off we went. I brought snacks and a drink to keep him occupied, and it worked! I was able to install him on a bench with a good view of the pond while I wandered off to take a few more pictures of the insect life around the wetlands, and found some new (to me) creatures and behaviors. It wasn't long before he grew hot and bored and "suggested" that we head home, but when a place is this teeming with life, it doesn't take long to get some pictures of it, either. One of the more common insects around the pond at this time of year is a tiger beetle; I'm not entirely sure which one it is, but I believe it to be the punctured tiger beetle, Cicindelidia punctulata. There are dozens, if not hundreds, of them flying around from spot to spot around the sandy margins of the wetlands, so if I get back there anytime soon I'll be sure to take more photos to get the ID. Here's the one shot from this trip that sort of turned out:
Tiger beetle, presumed Cicindelidia punctulata. Yamato Scrub, September 1, 2014

Tiger beetle, presumed Cicindelidia punctulata. Yamato Scrub, September 1, 2014

While not as showy as other tiger beetles (seriously, do an image search on tiger beetles and you'll see some amazing walking jewelry), it has a certain charm in the metallic sheen from its hard wing covers (elytra). Tiger beetles, true to their name, are predaceous, using their impressive speed, large eyes, and hefty mandibles to attack and consume their prey. I haven't seen them catching or eating anything, but by all accounts, it's impressive. However, and as sort of a follow-up to yesterday's post that featured a damsels in distress (that is, a damselfly eating another damselfly), today's post features a truly impressive feat of predation: a dragonfly, Eastern Pondhawk (Erythemis simplicicollis) feasting on another dragonfly, Blue Dasher (Pachydiplax longipennis):
Eastern Pondhawk (Erythemis simplicicollis) enjoying a repast of Blue Dasher (). Yamato Scrub, September 1, 2014.

Eastern Pondhawk (Erythemis simplicicollis) enjoying a repast of Blue Dasher (Pachydiplax longipennis). Yamato Scrub, September 1, 2014.

It was a bit windy, and I couldn't get as close to the subjects as I'd have liked, so the picture's a bit blurry, but it's pretty easy to see what's going on here. Like any good predator, the pondhawk here is feasting on the tastiest bits of its captured prey first—in this case, the face and brains. The dragonfly that's being eaten is a bit blurry in the shot above, so here's a shot of one of its brethren (who knows? maybe it's the exact same animal, as I didn't follow this one after I'd photographed it) displaying the same markings on its tail (what dragonfly people call its "abdomen") and thorax (that part of the insect where the four wings and six legs attach):
Blue Dasher (Pachydiplax longipennis), Yamato Scrub, September 1, 2014.

Blue Dasher (Pachydiplax longipennis), Yamato Scrub, September 1, 2014.

Come on out to the Yamato Scrub if you want to see some amazing examples of nature, "red in tooth and claw." Because, unlike on the maps of antiquity or the Renaissance, here indeed, there be dragons. (Well, dragonflies, at any rate.) And tigers. (Well, tiger beetles.) Etymological note: the genus of the tiger beetle pictured at top (Cicindelidia) appear to be derive its name from the latin word for glow-worm, cicindela. (There are two North American genera with similar names, Cicindela and Cicindelidia; presumably they are named so similarly because they are suspected to be closely related.) Tiger beetles do have a bit of a metallic sheen to them, which might account for the genus name, but I really have no idea...

After the rains, the odonates appear

South Florida is typically described as having two seasons: wet (May through October) and dry (November through April). Hydrologists like to split this up a bit further, with the wet season (now called high rainfall, low evapotranspiration season) running June through October, and the dry season now divided into two subseasons: low rainfall, low evapotranspiration (November through February) and a low rainfall, high evapotranspiration season (March through May). What this translates to in layman's terms seems to be something like "wet, then dry, then really dry." Over the last three years, two Aprils have been fairly wet (7.5 inches at my rain gauge this year, and a whopping 9.22 inches the previous year), while one was quite dry (in 2011 we had only 1.15 inches of rain in April). This year, May started off with a bang: Over six inches of rain in the first three days, five and a half of them in one long rainy day that also included at least one tornado here in Boca Raton (at my dentist's office, no less!). All that moisture falling from the sky, saturating the local soil, has an effect on wildlife. Saturday morning, after what seemed like forever, the yard was full of odonates again. Damselflies (Rambur's Forktails, Fragile Forktails, and Everglades Sprites) and dragonflies both (Blue Dasher, Little Blue Dragonlet, Eastern Pondhawk) were flitting around in the tall grass (after months without having to mow, I can see that I'll be back out on a weekly basis with my trusty reel mower—no gas for me!). Here's a shot I liked of one particularly patient Everglades Sprite (Nehalennia pallidula):
Everglades Sprite (Nehalennia pallildula). Boca Raton, FL, May 4, 2013.

Everglades Sprite (Nehalennia pallildula). Boca Raton, FL, May 4, 2013.

As usual, you can click on the image for a larger view. If you look closely, you can see the individual facets in the right eye:
Everglades Sprite (Nehalennia pallildula), detail. Boca Raton, FL, May 4, 2013.

Everglades Sprite (Nehalennia pallildula), detail. Boca Raton, FL, May 4, 2013.

As you may recall, those individual facets in the compound eye are called ommatidia. These tiny simple lenses, in combinations of hundreds (in the simplest compound eyes) to tens of thousands, form a complete image in the brain of the animal. The more ommatidia there are, the greater the visual acuity of the animal in question (in addition to insects, millipedes and mantis shrimp have compound eyes featuring ommatidia). In that respect, they function very much like the pixels on a CCD chip: as you add more pixels to your camera, you can create larger and larger images at high resolution. (Can you tell I got a new camera recently? One with a ridiculously high pixel count?) Another damselfly appeared a bit after I got tired of chasing those sprites around. This one is a Fragile Forktail (Ischnura posita):
Fragile Forktail (Ischnura posita). Boca Raton, FL, May 4, 2013.

Fragile Forktail (Ischnura posita). Boca Raton, FL, May 4, 2013.

And there was the ubiquitous Rambur's Forktail as well:  
Rambur's Forktail (<i>Ischnura ramburii</i>). Boca Raton, FL, May 4, 2013.

Rambur's Forktail (Ischnura ramburii). Boca Raton, FL, May 4, 2013.

Here's the first dragonfly I've managed to image so far this month; the Blue Dasher (at one point the most commonly photographed odonate on odonatacentral.org):
Blue Dasher dragonfly (Pachydiplax longipennis). Boca Raton, FL, May 4, 2013.

Blue Dasher dragonfly (Pachydiplax longipennis). Boca Raton, FL, May 4, 2013.

And here's the second. (Surprise, surprise! Another Blue Dasher):
Blue Dasher (Pachydiplax longipennis. Boca Raton, FL, May 4, 2013.

Blue Dasher (Pachydiplax longipennis. Boca Raton, FL, May 4, 2013.

And the third, a different species this time (Little Blue Dragonlet):
Little Blue Dragonlet (Erythrodiplax minuscula). Boca Raton, FL, May 4, 2013.

Little Blue Dragonlet (Erythrodiplax minuscula). Boca Raton, FL, May 4, 2013.

If this keeps up, it might be an interesting season for backyard wildlife after all!

Blue Dasher bonanza [updated Feb 2012]

pachydiplax_longipennis_obelisk_20101001
It was a lot of fun sitting out back proofreading this morning. The humidity is down, so the temperature, while "the same" according to the thermometer as it was before T.S. Nicole/T.D. 16 blew through, is a lot more livable. (It's starting to feel like fall; the typical way it arrives here in south Florida: an inch at a time, with lots of backsliding and sweating a la summer.) I'm not sure whether it's connected to the nicer weather, but we had what I would almost call an infestation of dragonflies today: mostly Blue Dashers, but a few larger skimmer species as well. They were dripping from every available perch in the backyard: shrubs, trees, telephone wires. They were in the oak trees in the front yard, on the streetlight (boo! hiss! light pollution!) wires. It was astonishing! Here are a couple of photos (male Blue Dashers, Pachydiplax longipennis) that turned out nicely: If you want to see what a real swarm of dragonflies looks like, or find out more about how and why they swarm, see this post on the dragonfly woman's website. All I know is today it was a lot of fun to be a backyard naturalist! [UPDATE: I'd been meaning to look up the origin of this species' name, which I keep misremembering as Brachydiplax. Turns out that pachy, which we all recognize from pachyderm, is Greek for thick. Plax, placos, is Greek for plate, tablet: anything wide and flat. Longipennis is Latin for long-winged (yes, 2 n's, people). So this species' name translates to "thick double-plated long wings." I'm not really sure if Burmeister, who named it in 1839, had that exact meaning in mind, but, since I haven't been able to get to a source telling me otherwise, this is what it means to me. If anyone out there has a better translation for me, I'd love to hear it. If you go to Needham and Westfall (1955; thanks, M!) or Needham, Westfall, and May (2000; I wish!), you can find this: "the genus is easily recognized by a single venational character: the single crossvein under the distal end of the [ptero]stigma has a vacant space, about as long as four normal cells, between it and the four postnodal crossveins of the second row. ... Length of wings not remarkable, though the specific Latin name makes reference to it. Shortness of abdomen in female gives impression of long wings." So the generic name might refer to that long empty spot under the pterostigma; I'm not sure if that's what Burmeister had in mind, but it's my working hypothesis.] [Update, February 2012: Thanks to the North American Odonata checklist of Dunkle and Paulson, I can now update the etymology of the generic and specific names: Pachydiplax means "thick Diplax," referring to the "stout female abdomen in comparison with members of the old libellulid genus Diplax"; "longipennis" does indeed mean long-winged, but D&P specify that it is in relation to the relatively short female abdomen." It's so nice to have an authoritative starting point for etymological information about these creatures!]