Odonates returning

As the calendar turns from January to February, damselflies and dragonflies are returning to the yard. Today three lovely male Citrine Forktails (Ischnura hastata) were in the back yard while I was baby sitting for three-year-old Daniel, home with a respiratory infection. (Yay, work from home.) While he was helpfully turning the back yard into mud, I was able to corral one of the damselflies near a lovely blue Salvia flower on the side of the house (it's not Tropical Sage, Salvia coccinea, but a new variety I picked up recently—long enough ago, though, that I forget which species it is):
Citrine Forktail (Ischnura hastata). Boca Raton, FL, February 3, 2015.

Citrine Forktail (Ischnura hastata). Boca Raton, FL, February 3, 2015.

Pretty as a picture. I just love these little guys. I saw one or two of them in the yard in January, but I'm pretty sure this is the first time this year we've had three at once.

Depth of field, part two

In my post last week I talked about how depth of field is critical to macro photography. I found a couple of photos of that Citrine Forktail where it's even more apparent, although it's a bit difficult to tease out what's a result of the angle at which the photo was taken (was the camera perpendicular to the long axis of the insect or not?) and what is due entirely to depth of field. I suspect that I might have inadvertently rotated the camera slightly. The first photo was taken at f/11, which is the "standard" aperture for macro photography out of doors. The region of best focus is centered on the damselfly's eye and the body is rather blurry:
depth_of_field_1

Ischnura hastata. f/11, 1/400. Eye in perfect focus, most of body blurry.

The second image is taken at an even smaller aperture, f/14, with a correspondingly greater depth of field. And while the eye isn't in as good a focus, the entire body is crisp and clear:
depth_of_field_2

Ischnura hastata. f/14, 1/250 exposure. Eye slightly blurry, body entirely in focus.

To get a better idea of what I mean when I say that the eye is in perfect focus in the top image and in not such perfect focus in the second image, here are cropped views of the two images:
The eye, legs, and thorax are in excellent focus.

The eye, legs, and thorax are in excellent focus.

Here is a cropped view of the eye in the second image. Notice how much less impact this crop has than the first one; it turns out that the eyes are critical to good insect photography. (If you don't agree that the first crop is better than the second one, click on the image to get the full size version; it should be much easier to see.)
The eye is not in perfect focus, but the thorax and the rest of the body are crisp and clear.

The eye is not in perfect focus, but the thorax and the rest of the body are crisp and clear.

The question is, how much of the difference is due to the slight difference in depth of field, and how much is due to any inadvertent camera rotation (or movement of the subject itself)? The only way to answer that is to have a guaranteed stationary camera (use a tripod) and a guaranteed stationary subject (difficult for wildlife photography). The trouble with tripods, of course, is that they're difficult to set up and to move in areas that are dense with vegetation, which just happens to be the type of area damselflies frequent. If by chance the insect alights in a cleared-off area, chances are that maneuvering a tripod into the area will be enough to scare it off. I'm tempted to try a monopod for two reasons: first, it will help steady the camera, even if it won't guard completely against rotation issues; second, it can serve as a walking stick and, in a pinch, to beat back brush, clear aggressive spiderwebs, etc.

Citrine forktail

Last week I started to notice the persistent presence in these here parts of those ephemeral and infernally hard to see odonates, the damselflies. Two forktail species, Rambur's and Citrine, (Ischnura ramburii and I. hastata, for those of you keeping score at home) are the only ones present so far, but I'm sure that soon I'll see the bluets again. I'm generally only able to go out on photo safari during the lunch hour (I do have a day job, after all), and I've found that the local damselflies are pretty wary in the middle of the day. But the other afternoon I was able to sneak up on one bright yellow male Ischnura hastata (Citrine Forktail); it was quiescent enough to allow me to discover the effects of depth of field on odonate photography. These animals are small, but in macro photography, small distances matter. As Sid Dunkle, coauthor of the recent monographic  guide to the damselflies points out, depth of field is critical to successful odonate photography.  In the photographic Supplement to Damselflies of North America, the standard treatment of the zygoptera, Dunkle writes that
I have had the near eye and the tip of the abdomen of a damselfly in focus, but the near surface of the thorax was out of focus! ... The film plane [or in my case, the CMOS chip] must be aligned exactly with the longitudinal axis of the body to get both head and tip of abdomen in focus. A lot of patience is needed!
In my case, patience was needed simply to approach these maddeningly elusive little beasts. I say maddening because one would expect that a relatively large and slow-flying animal like this would be pretty easy to keep track of once spotted. But nothing could be further from the truth. It might just be my aging eyes, but I found it quite difficult to keep my eye on these little buggers as they flew from brightly lit areas to shade, and from grass stem to grass stem. At times I found it easier to track them by their shadows than by their actual bodies! But once you get a damselfly quiet, it is indeed possible to approach them closely enough to capture some successful photographs, as the gallery below indicates. It's also possible to discover just how critical focusing is in macro photography. I took many more than seven photos, of course; these are just the ones that are anywhere close to being keepers, or that can serve as instructional reminders for myself.  

A romp in the grass with some fine damsels

ischnura_ramburii_wheel_20120424
The last few days have seen the finest weather I can recall since moving to Florida. Daytime highs in the low- to mid-70s, overnight lows in the 50s and 60s, a light breeze making sure that even when you're out in the sun you feel cool and refreshed. This is what living in south Florida is supposed to be like! When the weather's this nice, one of my favorite things to do during my lunch break is go out and get dirty. And every now and then, getting dirty involves rolling around in the grass chasing after lovely little damsels. And every now and then, when you chase lovely little damsels you catch them. Here are some pictures of the lovely little damsels I caught during my lunch break one day this week. A beautiful, if somewhat immature, female Citrine Forktail (Ischnura hastata): Doesn't she have just the loveliest orange color all up and down her body? Were she older, her color would be a bit duller: her abdomen would have blackened up and perhaps become pruinose (powdery/waxy white), her thorax (including her eyes) would have become greenish, and she'd generally look a little less like a bright orange/red sports car. The next day I saw her, or perhaps her sister or cousin, in the front yard: Still beautiful, right? This is more likely a sister or cousin, as our original little girl didn't have any nasty mites on her underbelly, and you can see in the picture above that this little lady has acquired such a hitchhiker. My understanding is that these mites are typically acquired during the damselfly's larval stage, and they just sort of hang around until they can begin feeding on the adult form. Next, illustrating the fact that nothing in the world escapes the indignity of being eaten, whether it will or no, two different forktails, a male Citrine and a female Rambur's are both dining and being dined upon. Reminds me of "Bugs" by Ogden Nash:

Some insects feed on rosebuds, And others feed on carrion. Between them they devour the earth. Bugs are totalitarian.

—Ogden Nash

See the little mites under the thorax of this male Citrine Forktail? They probably bug him a little bit, but from all accounts, unless they are quite numerous they don't seem to measurably affect his quality of life. April must really be the month for Citrine Forktail here in Boca; my yard has been veritably plagued by them for weeks now (if you can call the presence of beautiful little insectivorous fliers a plague). Just to show how many there were, here are a male and immature female jockeying for space on the same wildflower/weed in my front yard: And now, toward the end of the month, their larger cousins, Rambur's (I. ramburii) are showing up as well: The female in the picture above has captured a nice juicy prey item (looks like a leafhopper) and is happily munching away at it, all the while being happily munched upon in her turn by those leetle tiny mites on the right side of her thorax. (It's thought that, like the lice on birds, the mites on each species of odonate are separate species. Can you imagine how abundant parasite species must be, if there's at least one separate species for each host species on the planet? One study of just one type of parasite (gregarines, one-celled protozoans) demonstrated that these organisms tend to be host-specific as well, so when you add up the number of kinds of parasites, then multiply by the number of known species of hosts, you're dealing with astronomical quantities.) The female of Rambur's Forktail is polymorphic, which means that she comes in more than one color form (but only one per customer, please). The individual pictured has what is known as andromorph coloration (from Greek andro-, "male"); that is, her color is almost exactly like that of the male. Her thorax, though, unlike the green thorax of the male, is blue. This color difference means that she is technically immature; if she were older, it would be green just like the male's. How can I prove that she's female? Well, today it was pretty easy: she's the one on the bottom in the wheel, or heart, position: Why on earth, you might ask, do these damselflies have to resort to such an odd position for copulation? Well, you see,
Male Odonata are unique among exopterygote insects [ie, those that undergo incomplete metamorphosis, with only egg-larva-adult stages of life, rather than complete metamorphosis, egg-larva-pupa-adult] in having the primary genital orifice and the intromittent organ located at opposite ends of the abdomen. (Corbet 1999)
During copulation, the female's tail tip is pressed up against a secondary genital structure located between the male's second and third abdominal segments. That structure, called the seminal vesicle, has been packed  with sperm from abdominal segment 9, right near his own tail tip—how he manages to first clasp the female and then transfer the sperm would be a complete mystery to me were it not for the helpful illustration from Corbet that I reproduce below—and is being pressed up against the female's tail tip so the sperm can be transferred from said vesicle to her spermatheca; any eggs that pass through that spermatheca then become fertilized. Here is a graphic representation of the process from the dean of odonate studies, Philip Corbet (you have to click the image to see all 8 stages; the thumbnail cuts the picture off mercilessly): The process looks inordinately complicated to our anthropocentric eyes, but it's worked for odonates, both damsel- and dragonfly, for millions of years longer than primates have been wandering the earth. And here, just because they came out nicely, are a couple more shots of the beautifully colored male Citrine Forktail: References Corbet, P.S. (1999). Dragonflies: Behavior and Ecology of Odonata. Ithaca and NY: Comstock. Paulson, D. (2011). Dragonflies and Damselflies of the East. Princeton, NJ: Princeton UP.  

New backyard bug: Ischnura hastata (Say)

ischnura_hastata_20120409
Some insects look so delicate and fragile that it's hard to remember that they can be among the most ferocious predators, at least for their size, on the planet. Case in point: the tiny little yellow damselfly Ischnura hastata, commonly known as the Citrine Forktail. It's only about an inch long and its wings look so delicate and flimsy it's a wonder that it can fly at all: But the damselfly, like its larger cousin the dragonfly, is a voracious predator both as larva and imago (adult). According to the most recent (and best) field guide published on odonates of the eastern United States,
Odonates are all predators, in both adult and larval stages... Most dragonflies take small prey, much smaller than themselves. Tiny flies, leafhoppers, and beetles are common prey. Some species vary these with larger prey, for example other dragonflies and butterflies, and others seem to be specialists on large prey... [S]ome pond damsels will take another damselfly of the same size, especially when the latter has just emerged and is quite vulnerable. Note that dragonflies that routinely take large prey are among the most effective biters when captured!

[Paulson 2011]

I've never been bothered by biting dragonflies or damselflies, but then, I've not yet invested in an insect net to capture any, either, so perhaps I should just leave that alone. My preferred mode of capturing insects is via my camera's imaging chip.

There have been relative hordes of damsels in the front and back yards lately; I suppose that means spring has sprung. Cheers!

Oops! Almost forgot the etymology.

It took some searching, but this Italian paper finally gave me the origin of the genus name Ischnura:

Ischnura - ισχηοσ = gracile + ουρα, ασ = coda; dalla coda gracile. Per la forma esile dell’addome.
My Italian is a mite rusty, but it looks like it means "from the gracile [a hifalutin English word meaning slender] tail. For the slender form of the abdomen." As for the species name hastata, that presumably comes from the Latin hasta, "spear." So this tiny little damselfly's taxonomic name basically translates to "slender spear." Say's original genus name for this species was Agrion, which presumably came from Greek agrios, wild. So "wild spear" was what he had in mind when naming this species, which later came under the older genus name, Ischnura.