Archive for the ‘Photoshop’ Category

Mocha Emerald dragonfly claspers

July 13, 2017

Mocha Emerald dragonfly (Somatochlora linearis) was spotted along a small creek at a remote location in the forest at Huntley Meadows Park. This individual is a male, as indicated by his terminal appendages and hamules.

All male dragonflies have three terminal appendages, collectively called “claspers,” that are used to grab and hold female dragonflies during mating: an upper pair of cerci (“superior appendages”) and a lower unpaired epiproct (“inferior appendage”).

09 JUL 2017 | Huntley Meadows Park | Mocha Emerald (male)

(See a full-size version of the original photo, without annotation.)

09 JUL 2017 | Huntley Meadows Park | Mocha Emerald (male)

(See a full-size version of the original photo, without annotation.)

Male dragonfly secondary genitalia, called hamules, are located below abdominal segments two and three (S2 and S3), as shown in the following annotated image. Hamules come in a variety of sizes and shapes, but their function is identical for all species of odonates.

hamules: paired structures that project from genital pocket under second segment and hold female abdomen in place during copulation Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 11618-116198). Princeton University Press. Kindle Edition.

09 JUL 2017 | Huntley Meadows Park | Mocha Emerald (male)

(See a full-size version of the original photo, without annotation.)

Technique Hint: Did you notice that the “focus” of each photo (not to be confused with the focus point) is shown against a lighter background? That’s no accident — I composed each shot that way. As a result, the terminal appendages (cerci and epiproct) are much easier to see in the first two photos than the last shot, in which the composition highlights the hamules.

Copyright © 2017 Walter Sanford. All rights reserved.

Calico making the case for claspers

June 27, 2017

A Calico Pennant dragonfly (Celithemis elisa) was spotted at Painted Turtle Pond, Occoquan Bay National Wildlife Refuge (OBNWR), Prince William County, Virginia USA.

Mature adult female Calico Pennants are yellow; mature adult male Calico Pennants are red. So the following individual must be female, right? Wrong!

20 JUN 2017 | OBNWR | Calico Pennant (immature male)

This individual is an immature male, as indicated by his terminal appendages and yellow coloration.

Male dragonflies have three terminal appendages, collectively called “claspers,” that are used to grab and hold female dragonflies during mating: an upper pair of cerci (“superior appendages”); and a lower unpaired epiproct (“inferior appendage”).

20 JUN 2017 | OBNWR | Calico Pennant (immature male)

(See a full-size version of the original photo, without annotation.)

In contrast, female dragonflies have a pair of cerci (superior appendages) that have little or no function.

20 JUN 2017 | OBNWR | Calico Pennant (female)

(See a full-size version of the original photo, without annotation.)

Color can be a deceptive field marker. Immature males appear similar to immature females of the same species (and some mature females) for many types of dragonflies that display sexual dimorphism. This is true for many members of Family Libellulidae (Skimmers), such as Calico Pennant. Terminal appendages may be used to differentiate gender for many species of dragonflies.

20 JUN 2017 | OBNWR | Calico Pennant (immature male)

Related Resource: Odonate Terminal Appendages — single-topic field guides for dragonflies and damselflies featuring both text and annotated photos.

Copyright © 2017 Walter Sanford. All rights reserved.

“Record shot”

June 21, 2017

As a wildlife photographer with a focus on insect photography, one of my mantras is: “Get a shot, any shot; refine the shot.” In other words, don’t miss the opportunity to document a spotting by trying to get a great shot first.

11 JUN 2017 | Fluvanna County, VA | Dragonhunter (male)

The preceding photograph — heavily-cropped in order to compensate for the distance to the subject — is a “record shot” (at best) of a male Dragonhunter dragonfly (Hagenius brevistylus) that was spotted at the Hardware River Wildlife Management Area, Fluvanna County, Virginia USA.

The dragonfly was photographed from the banks of the Hardware River, approximately 20 feet above the water. Distance seems to be compressed in the photo, an effect of the mid-range telephoto lens used to take the shot. The Dragonhunter was perching ~10 feet above the water. I settled for a “record shot” since there was no way to get closer to the subject.

Tech Tips

The photo was taken using a Fujifilm X-T1 digital camera, Fujinon 55-200mm zoom lens, and Fujifilm EF-X500 shoe mount flash. Adobe Photoshop was used to remove a small distracting element from the left edge of the photo.

Editor’s Note

Thanks to fellow Virginians Karen Kearney and Mike Boatwright for adding the phrase “record shot” to my vocabulary.

Copyright © 2017 Walter Sanford. All rights reserved.

Cobra Clubtail external reproductive anatomy

May 28, 2017

I liked to make paper- and plastic models when I was a child. Seems like the directions for assembling many models — not that anyone reads the directions — always started by saying something like “Insert Tab A in Slot B.”

Oddly enough, that line reminds me of how odonates copulate, in general, and Cobra Clubtail dragonflies (Gomphurus vastus) in particular.

Male

The hamules are “Tab A.”

Female

The subgenital plate is “Slot B.”

Putting it all together

Insert Tab A in Slot B. That’s the PG-rated version of how Cobra Clubtail dragonflies copulate in order to reproduce.

The Backstory

There is an annual mass emergence of Cobra Clubtails during the first week-or-two of May at Riverbend Park. It’s a spectacular event worth seeing firsthand!

The following photo shows a dead female, one of several Cobra Clubtails that were trampled by groups of elementary school children visiting the park on 09 May 2017. Her premature death saddens me because it was avoidable — the students should have been warned to watch their step because there were lots of Cobra Clubtails perching on the ground almost everywhere.

In the hope the female didn’t die in vein, I reluctantly decided to photograph the corpse in order to illustrate her external reproductive anatomy.

Editor’s Note: Sincere thanks to Dennis Paulson for help in identifying the female parts on the ventral side of abdominal segments eight and nine (S8-9).

Copyright © 2017 Walter Sanford. All rights reserved.

Common Baskettail (terminal appendages)

May 18, 2017

A male and female Common Baskettail dragonfly (Epitheca cynosura) were spotted recently at the same location in Fairfax County, Virginia USA.

Male and female Common Baskettails look similar. Terminal appendages can be used to identify gender.

Male

Male dragonflies have three terminal appendages, collectively called “claspers,” that are used to grab and hold female dragonflies during mating: an upper pair of cerci (“superior appendages”); and a lower unpaired epiproct (“inferior appendage”).

03 MAY 2017 | Fairfax County, VA | Common Baskettail (male)

(See a full-size version of the original photo, without annotation.)

Female

Female dragonflies have a pair of cerci (superior appendages) that have little or no function. The abdomen of female Common Baskettails is noticeably thicker than males of the same species.

03 MAY 2017 | Fairfax County, VA | Common Baskettail (female)

(See a full-size version of the original photo, without annotation.)

A better view of the subgenital plate is provided by the following digital scan of the underside of the abdomen of a female Common Baskettail. The subgenital plate looks a little like a pair of calipers. Also known as vulvar lamina, the subgenital plate is located under the ninth abdominal segment (S9) of some female odonates and “serves to hold eggs in place during exophytic oviposition.” Remember that all dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back.

Image used with permission from Ed Lam.

Copyright © 2017 Walter Sanford. All rights reserved.

Lancet Clubtail dragonflies (males)

May 14, 2017

At least two Lancet Clubtail dragonflies (Phanogomphus exilis) were spotted during a photowalk along a mid-size stream in Fairfax County, Virginia USA.

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

These individuals are males, as indicated by their terminal appendages and indented hind wings.

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

The next photograph was taken at a later time than the first two photos. All of the photos in this post were taken near the same location. Is this another male, or the same one featured in the preceding photos? Who knows?

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

Lancet Clubtail versus Ashy Clubtail

Lancet Clubtail looks similar to Ashy Clubtail (Phanogomphus lividus). The only way to differentiate the two species with certainty is to examine their external reproductive anatomy; this is impossible unless the specimens are captured and examined in-hand.

Relative size is used sometimes to identify the two species: Lancet Clubtail is slightly smaller than Ashy Clubtail. There are two problems with this method of identification. First, it is virtually impossible to determine the exact size of a specimen in the field unless it is captured and measured. Second, some natural variation in size should be expected among individuals of the same species.

A quick-and-dirty method for differentiating Lancet- and Ashy Clubtails with some degree of certainty is to look at the markings on abdominal segments eight and nine (S8-9). Lancet Clubtail has a “spearpoint” on top of abdominal segment eight (S8) that almost reaches the end of the segment, a wide yellow stripe on top of segment nine (S9), and irregular yellow markings on the sides of segments eight and nine (S8-9).

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

(See a full-size version of the original photo, without annotation and inset photo of Ashy Clubtail.)

In contrast, Ashy Clubtail has a spearpoint on top of abdominal segment eight (S8) that is less than half the length of the segment, segment nine (S9) may or may not have a pale yellow stripe on top, and the sides of segments eight and nine (S8-9) may or may not have “poorly defined” yellow markings.

03 MAY 2017 | Fairfax County, VA | Ashy Clubtail (male)

(See a full-size version of the original photo, without annotation.)

Coloration is variable among individuals of the same species, so looking at abdominal markings isn’t always a reliable method of identification. In this case, it works beautifully.

Editor’s Note: The word “spearpoint” and the phrase “poorly defined” are descriptors attributed to Dennis Paulson, Dragonflies and Damselflies of the East (Princeton Field Guides). Princeton University Press. Kindle Edition.

Copyright © 2017 Walter Sanford. All rights reserved.

Spine-crowned Clubtail (terminal appendages)

May 10, 2017

A male and female Spine-crowned Clubtail dragonfly (Hylogomphus abbreviatus) were spotted recently in Fairfax County, Virginia USA.

Male

Male dragonflies have three terminal appendages, collectively called “claspers,” that are used to grab and hold female dragonflies during mating: an upper pair of cerci (“superior appendages”); and a lower unpaired epiproct (“inferior appendage”). The epiproct for Spine-crowned Clubtail is essentially a wide plate with two prongs.

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

(See a full-size version of the original photo, without annotation.)

The hind wings of male clubtail dragonflies are “indented” near the body, as shown in the preceding photograph. In contrast, the hind wings of female clubtails are rounded (shown below). Also notice the right hind wing of the male is slightly malformed.

Female

Female dragonflies have a pair of cerci (superior appendages) that have little or no function. The abdomen of female Spine-crowned Clubtails is noticeably thicker than males of the same species.

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (female)

(See a full-size version of the original photo, without annotation.)

Copyright © 2017 Walter Sanford. All rights reserved.

Spine-crowned Clubtail dragonfly (male)

May 8, 2017

A Spine-crowned Clubtail dragonfly (Hylogomphus abbreviatus) was spotted recently in Fairfax County, Virginia USA. Spine-crowned Clubtail is relatively uncommon in Northern Virginia, and a new species of dragonfly for my life list.

This individual is a male, as indicated by his terminal appendages and indented hind wings. Notice the right hind wing is slightly malformed.

Spine-crowned Clubtail versus Cobra Clubtail

Spined-crowned Clubtail looks similar to Cobra Clubtail (Gomphurus vastus). Two field markers can be used to differentiate the species.

Spine-crowned Clubtail features large yellow spots on the sides of abdominal segments eight and nine (S8-9); Cobra Clubtail has a small yellow spot on the side of abdominal segment eight (S8) and a large yellow spot on the side of abdominal segment nine (S9), as shown below (see inset photo).

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

(See a full-size version of the original photo, without annotation and inset photo.)

The face of Spine-crowned Clubtail is yellow and unmarked; the face of Cobra Clubtail is yellow with horizontal black markings (see inset photo).

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

(See a full-size version of the original photo, without inset photo.)

More photos, Spine-crowned Clubtail

This guy was a cooperative model as I followed him to several perches on rocks along a large stream.

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

Editor’s Notes: Special thanks to Mike Boatwright, curator of the Virginia Odonata Facebook group, for help in verifying my tentative field identification. As far as I know, this is the first official record for Hylogomphus abbreviatus in Fairfax County, Virginia.

Copyright © 2017 Walter Sanford. All rights reserved.

Epitheca cynosura exuvia

April 26, 2017

On 13 April 2017, a late-stage emergent teneral female Common Baskettail dragonfly (Epitheca cynosura) was observed at Painted Turtle Pond during a photowalk around Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

Several dragonfly exuviae were collected near the same location as the emergent teneral female. All of the exuviae look identical, although there is some variation in size. A two-step process was used to verify the genus and species for one of the larger exuvia.

  • Determine the family.
  • Determine the genus and species.

This specimen is approximately 22 mm (~0.87 in) in length.

Step 1. Family

First, determine the family of the specimen. For reference, watch the excellent Vimeo video, Identifying dragonfly larva to family (8:06). Here’s the decision tree used to identify the exuvia as a member of the Family Corduliidae (Emeralds).

  • The specimen has a mask-like labium that covers the face, characteristic of four families: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).
  • There is no horn on top of the face-head, characteristic of Macromiidae, so it’s not a cruiser.
  • Cordulegastridae has jagged crenulations on its labium, so it’s not a spiketail. The crenulations for Corduliidae and Libellulidae look similar.
  • Look at the anal pyramid to differentiate Corduliidae and Libellulidae [See Photo No. 7.]: It’s probably Corduliidae if the cerci are at least half as long as the paraprocts. [Editor’s Note: It’s probably Libellulidae if the cerci are less than half the length of the paraprocts.]

In summary, the exuvia has a mask-like labium with relatively smooth crenulations, no horn on its face-head, and the cerci are more than half as long as the paraprocts, confirming that the specimen is a member of Family Corduliidae (Emeralds).

(See a full-size version of the original photo, without annotation.)

Notice that dorsal hooks are present and well developed on most abdominal segments.

No. 4 | Common Baskettail (Epitheca cynosura) | exuvia (dorso-lateral)

A lateral view of the exuvia provides a good look at the labium, also known as the mentum, a two-segment hinged “jaw” that is used to grab food: the prementum is the segment of the labium closer to the mouth; the postmentum is the segment closer to the base of the head.

The white filaments that extend from the split in the thorax (as shown in Photo No. 1-7) are breathing tubes, artifacts of the unique respiratory system of dragonfly nymphs.

(See a full-size version of the original photo, without annotation.)

A closer view of the head shows two “bumps” that may be a pair of tubercles.

Step 2. Genus and species

Characters from Identification Keys to Northeastern Anisoptera Larvae, dichotomous keys compiled by Ken Soltesz, were used to identify the genus and species for the exuvia. Although palpal/mental setae were not examined, all other characters match Epitheca cynosura.

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

Alternate Key to the Genera of the Family Corduliidae, p. 29.

Key to the species of the genus (subgenus) Tetragoneuria, p. 32.

No. 7 | Common Baskettail (Epitheca cynosura) | exuvia (anal pyramid)

(See a full-size version of the original photo, without annotation.)

The last photo shows a ventral view of the exuvia. The vestigial hamuli located between abdominal segments two and three (S2-3) strongly suggests this individual is a male, therefore this specimen probably is not the same exuvia from which the teneral female emerged.

(See a full-size version of the original photo, without annotation.)

Tech Tips:

The following equipment was used to shoot all of the preceding photographs: Canon EOS 5D Mark II digital camera, in manual mode; Canon EF100mm f/2.8L Macro lens (set for manual focus) plus a Kenko 20mm macro automatic extension tube; Canon 580EX II external flash tethered to the camera by a coiled six-foot Vello Off-Camera TTL Flash Cord for Canon Cameras, off-camera, in manual mode; the Canon flash optically triggered a small Nissin i40 external flash (in SF mode) used for backlight; and a Sunpak LED-160 Video Light with a white translucent plastic filter used for side light.

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resources:

Editor’s Note: Sincere thanks to Sue Gregoire, Kestrel Haven Migration Observatory, for verifying my tentative identification, and for sharing some good odonate nymph knowledge regarding vestigial hamuli!

Copyright © 2017 Walter Sanford. All rights reserved.

Non-stop flight

April 22, 2017

On 18 April 2017, a Common Baskettail dragonfly (Epitheca cynosura) was spotted patrolling part of the shoreline at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a male, in flight.

108mm (600mm equivalent) | ISO 100 | f/5.2 | 1/800s | -1 ev | flash fired

The photograph was taken using a Panasonic LUMIX DMC-FZ150 superzoom bridge camera and a Canon 580EX Speedlite external flash set for manual mode at 1/8 power and 105mm zoom.

Related Resource: Stop-action photography of dragonflies in flight, a blog post by Walter Sanford, features Phil Wherry’s answer to my question “How fast would the camera shutter speed need to be in order to freeze all motion of a dragonfly in flight?”

Copyright © 2017 Walter Sanford. All rights reserved.


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