Archive for the ‘education’ Category

Springtime Darner (male claspers)

May 19, 2018

A Springtime Darner dragonfly (Basiaeschna janata) was spotted along Popes Head Creek at Hemlock Overlook Regional Park (HORP) in Fairfax County, Virginia USA. This individual is a male, as indicated by his terminal appendages and “indented” hind wings.

23 APR 2017 | HORP | Springtime Darner (male)

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

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”).

23 APR 2017 | HORP | Springtime Darner (male)

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

Editor’s Notes

The preceding photos are new, that is, previously unpublished. Both photos are full-frame (uncropped). Springtime Darners can be quite skittish. In this case, I was very close to an unusually cooperative model.

The last photo was shot using Aperture Priority. I prefer shooting in Shutter Priority, but I like to shoot a few shots using Aperture Priority whenever I can use either a monopod or tripod. In this situation, I improvised.

In addition to my photography gear, I usually carry a Coleman camp stool when I go photowalking. The small, lightweight folding chair is good for resting while waiting for “the game to come to me.” The camp stool also enables me to get closer to subjects either on- or near the ground, such as the Springtime Darner featured in this blog post. I think it’s easier to hold my camera rock-steady when I’m sitting on the chair with my elbows resting on my knees.

Copyright © 2018 Walter Sanford. All rights reserved.

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Twin-spotted Spiketail (male claspers)

May 17, 2018

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”).

Male members of the Family Cordulegastridae (Spiketails), including male Twin-spotted Spiketail dragonflies (Cordulegaster maculata), have relatively small cerci (terminal appendages) that can be mistaken for female cerci.

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.

Related Resources

Copyright © 2018 Walter Sanford. All rights reserved.

Brown Spiketail dragonfly (male claspers)

May 15, 2018

Brown Spiketail dragonflies (Cordulegaster bilineata) were spotted on two days during May 2018 at Occoquan Regional Park. Both individuals featured in this post are male, as indicated by their terminal appendages and slightly “indented” hind wings.

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”).

Notice the epiproct for Brown Spiketail is a wide “plate” that spans both cerci, as shown in the full-size version of the following annotated image.

Male dragonfly secondary genitalia, called hamules, are located below abdominal segments two and three (S2 and S3), as shown in the preceding annotated image. Hamules come in a variety of sizes and shapes, but their function is identical for all species of odonates. Some species of dragonflies and damselflies — such as Ashy Clubtail versus Lancet Clubtail and Southern Spreadwing versus Sweetflag Spreadwing, to name a few — can be differentiated/identified with certainty only by examining the hamules under magnification.

Copyright © 2018 Walter Sanford. All rights reserved.

Common Whitetail (immature males)

May 7, 2018

A first-of-season Common Whitetail dragonfly (Plathemis lydia) was spotted perching on the ground near a vernal pool at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is an immature male, as indicated by his terminal appendages, brown colored abdomen, and pattern of wing spots.

30 APR 2018 | Huntley Meadows Park | Common Whitetail (immature male)

Another immature male was spotted along an informal trail at a remote location in the park.

30 APR 2018 | Huntley Meadows Park | Common Whitetail (immature male)

Young male Common Whitetails begin to develop white pruinescence that changes the color of their abdomen from brown to white, hence the common name for this species.

Sexing Common Whitetail dragonflies

For many of the common species of odonates found in Northern Virginia, I created a collection of annotated guides that illustrates how to differentiate gender by looking at terminal appendages. The difference in the pattern of wings spots for male and female Common Whitetails is sufficient to identify gender.

Copyright © 2018 Walter Sanford. All rights reserved.

Blue Corporal (teneral males)

May 3, 2018

Several teneral male Blue Corporal dragonflies (Ladona deplanata) were spotted near Painted Turtle Pond during a photowalk at at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

Teneral/immature/young male Blue Corporals look similar to females of the same species. Terminal appendages can be used to differentiate gender: males have three (3) appendages; females have two (2).

Some of the ground cover is charred from a recent controlled burn at Occoquan Bay NWR.

The common name for Blue Corporal is derived from two cream-colored stripes that appear on the front of the thorax, similar to the two stripes that signify the rank of corporal in the military. As a mature male, those stripes will be partially obscured by dark blue pruinescence.

Related Resource: Blue Corporal (teneral females).

Copyright © 2018 Walter Sanford. All rights reserved.

Blue Corporal (teneral females)

May 1, 2018

Lots of Blue Corporal dragonflies (Ladona deplanata) were spotted near Painted Turtle Pond at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. This is the first time the author has observed Blue Corporal at Painted Turtle Pond.

Both individuals featured in this post are teneral females, as indicated by their tenuous wings and terminal appendages.

Female 1

The first female was spotted perching on vegetation near the shoreline of Painted Turtle Pond. Some of the ground cover is charred from a recent controlled burn at Occoquan Bay NWR.

The common name for Blue Corporal is derived from two cream-colored stripes that appear on the front of the thorax, similar to the two stripes that signify the rank of corporal in the military.

Notice the abdomen of this female seems to be bent slightly to the right (facing forward). This malformation probably occurred during emergence.

Female 2

The last female was spotted perching on the gravel road leading to Painted Turtle Pond. The purple rock located in the upper-right corner of the photo might contain the mineral fluorite.

Like many teneral dragonflies, if not most, this individual was quite skittish. I followed the female to two locations before calling the photowalk a wrap.

Related Resource: Blue Corporal (teneral males).

Copyright © 2018 Walter Sanford. All rights reserved.

Focus stacking workflow

April 15, 2018

By trial and error, the workflow that I use to create focus-stacked composite images has been refined to its current semi-steady state. My goal for the workflow is to maximize efficiency and minimize unexpected results. I’m not saying this is the best way to focus stack images, but it is the best way I have found to do it…so far. Suggestions for improvement are invited and welcome.

Photo editing using Apple Aperture… [or Lightroom]

Although Apple discontinued development of/support for Aperture years ago, the desktop application still works and in many ways I prefer Aperture over Lightroom.

Make all necessary edits/adjustments to one photo except Spot & Patch, Vignette, and BorderFX (a plug-in for Aperture). This process works because I shoot the entire photo set for a composite image using manual exposure and manual flash. Add metadata (IPTC and Keywords).

  • Right-click on the photo; select “Lift Adjustments.” <Replace> <Stamp Selected Images>.
  • Right-click on the photo; select “Lift Metadata.” <Replace> <Stamp Selected Images>.
  • Select all images for focus stack; Photos / Edit with Adobe Photoshop CC 2017.app…

Editor’s Note: Aperture seems to “choke” when too many photos are selected to send to Photoshop. Alternate procedure: Select the images (to be focus stacked); export as TIFFs (16-bit), 300 dpi; save in folder entitled either “TIFF” or “TIFF versions.”

Focus stacking workflow using Adobe Photoshop…

Launch Photoshop.

  • File / Scripts / Load Files into Stack…; either Add Open Files <OK> or browse to the location of the folder where the TIFF files are saved. Do not check the box for “Create Smart Object after Loading Layers.” By default, Photoshop creates a new document called “Untitled1”; either rename the document or leave it as is.
  • Select all layers.
  • Edit / Auto-Align Layers; Auto <OK>.
  • Edit / Auto-Blend Layers; Stack Images, Seamless Tones and Colors <OK>.
  • Duplicate all masked layers to a new document [backup copy].
  • Select Untitled1: Layer / Merge Layers (Photoshop merges all layers into one TIFF, named after the first file in numeric sequence.)
  • Straighten and Crop as necessary.
  • Duplicate the layer [or drag the layer to the copy icon (at the bottom of the Layers panel)].
  • Spot image (zoom in): Spot Healing Brush: 27-54 pixels, Content-Aware.
  • Duplicate the layer [or drag the Spot layer to copy icon].
  • Select the top layer: Filter / Other / High Pass…; adjust the radius until you can just see an outline of subject <OK>; change Normal to Overlay. Don’t oversharpen! I set the radius to around 5.4 pixels or less for composite images; ~1.5 pixels for single photos.
  • Duplicate the finished layers to a New document, temporarily called “Temp1.”
  • Save documents: Untitled1 (Save As… TIFF); backup copy of masked layers (Save As… PSD); Temp1 (Save As… PSD; change name to Untitled1.psd after the file is saved).
  • Import the composite TIFF file into Aperture [or Lightroom]: add additional keywords, as appropriate; Export using BorderFX.

Adobe Photoshop | High Pass Filter

Related Resource: High Pass Filter: Ep 134: Exploring Photography with Mark Wallace (10:13).

Copyright © 2018 Walter Sanford. All rights reserved.

Phanogomphus lividus exuvia

April 5, 2018

The Backstory

An Ashy Clubtail dragonfly (Phanogomphus lividusnymph was collected by Bob Perkins. (The date and location where the specimen was collected are unknown.) The nymph was reared in captivity until it emerged on 21 March 2017 and metamorphosed into an adult female. This specimen is the exuvia from the nymph. P. lividus is a member of the Family Gomphidae (Clubtails).

A two-step process was used to verify the identity of the exuvia.

  1. Determine the family.
  2. Determine the genus and species.

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 Gomphidae (Clubtails).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in Photo No. 1 and 3.
  • Antennae are club-like (not thin and thread-like, as in  Aeshnidae larvae), as shown in Photo No. 1.

It’s simple and straightforward to recognize this specimen is a clubtail.

No. 1 | Ashy Clubtail (Phanogomphus lividus) | exuvia (face-head)

Step 2. Genus and species

Lateral spines are present on abdominal segments six through nine (S6-S9).

The superior caudal appendage (epiproct) is as long as inferiors (paraprocts), as shown in Photo No. 4. The view of the terminal appendages is still slightly obscured by debris after the specimen was cleaned, making it challenging to distinguish the cerci from the paraprocts. Nonetheless, the epiproct and paraprocts appear to be nearly the same length.

The median lobe of the labium (prementum) is straight-edged, as shown in Photo No. 5.

After emergence

The next photograph shows the Ashy Clubtail dragonfly after emergence from one of Bob Perkins‘ holding tanks. Phanogomphus lividus is 48-56 mm in total length (Paulson, 2011).

Image used with permission from Bob Perkins.

This individual is a female, as indicated by its rounded hind wings and terminal appendages.

Image used with permission from Bob Perkins.

Related Resource

The dichotomous key for Gomphus (now Phanogomphus) that appears on p. 20 in Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz, was used to attempt to verify the genus and species of the exuvia. Markers that match this specimen are highlighted in boldface green text. Three boldface green asterisks (***) are used to highlight the thread for identification of P. lividus. Disclaimers are highlighted in boldface red text.

1a. Lateral spines on abdominal segments 7 to 9 (very minute if present on 6). [2]
***1b. Lateral spines on abdominal segments 6 to 9 well developed. [3]

3a. Superior caudal appendage (epiproct) shorter than inferiors (paraprocts); Teeth on lateral lobes of labium obsolete or poorly developed. [quadricolor]
***3b. Superior caudal appendage (epiproct) as long as inferiors (paraprocts); Teeth on lateral lobes of labium well developed. [4]

***4a. Median lobe of labium straight-edged. [lividus]
4b. Median lobe of labium convex-edged. [5]


Note: The weakest aspect of this key is couplet 4, as it applies to Gomphus descriptus [Harpoon Clubtail], the difference in the “convexity” of the median lobe between lividus and descriptus being very slight and difficult to discern in practice. Donnelly (pers. comm.) has found that, at least with New York specimens, the posterior narrowing of the median lobe of the labium is more abrupt in livid, and relatively gradual in descriptus. Also, the labial teeth are better developed in livid than in descriptus. These characters are so relative that any unknown suspected of being either of these species should be compared to reference specimens.

Tech Tips

The following equipment was used to shoot Photo No. 2 and 3: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode. Photo No. 1, 4, and 5Canon MP-E 65mm Macro lens (manual focus only, set for either 2x or 3x magnification) plus the multiple-flash setup.

Photo No. 1-3 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017.

Bob Perkins’ photos were shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Copyright © 2018 Walter Sanford. All rights reserved.

Ashy Clubtail exuvia focus stack

March 30, 2018

The Backstory

An Ashy Clubtail dragonfly (Phanogomphus lividus) nymph was collected by Bob Perkins. (The date and location where the specimen was collected are unknown.) The nymph was reared in captivity until it emerged on 21 March 2017 and metamorphosed into an adult female. This specimen is the exuvia from the nymph. P. lividus is a member of the Family Gomphidae (Clubtails).

Tech Tips

The preceding image is a composite of 39 photos taken using the following equipment: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (manual focus only, set for 3x magnification); and Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode.

Adobe Photoshop CC 2017 was used to focus stack the photos and post-process the final output.

According to the “Focus Stacking Step Size Calculator” embedded in the “Focus Stacking” Web page, the “safe step size” is 0.213 mm for an aperture of f/11 at 3x magnification using a full-frame DSLR. That’s right, 0.213 mm! The safe step size is the incremental distance at which the in-focus areas of two photos overlap. The ruler on the inexpensive focus rail that I use is marked in millimeters only, so I attempted to move the focus rail in tiny increments in two passes: one pass moving from front-to-back; and a second pass from back-to-front.

Copyright © 2018 Walter Sanford. All rights reserved.

Previews of coming attractions

March 28, 2018

Several test photos were taken for an upcoming identification guide for exuviae from Slaty Skimmer dragonfly (Libellula incesta).

The exuvia has a mask-like labium with smooth crenulations, indicating this specimen is a member of the Family Libellulidae (Skimmers), the largest family of dragonflies.

No. 1 | Libellula incesta | exuvia (face-head-dorsal)

Also notice the exuvia has “pointed” eyes, rather than “rounded” eyes like the exuvia from a Carolina Saddlebags dragonfly (Tramea carolina) shown below.

No. 2 | Tramea carolina | exuvia (face-head)

The pointed- versus rounded eyes dichotomy is a somewhat subjective decision, but if you make the right choice then this marker can be used to narrow the range of possible Libellulidae genera.

Exuviae from three genera of Libellulidae have pointed eyes: Libellula (18 species); Orthemis (3 species); and Plathemis (2 species). Slaty Skimmer (Libellula incesta) is one of 18 species in the genus Libellula.

Exuviae from all other genera of Libellulidae have rounded eyes.

No. 3 | Libellula incesta | exuvia (dorsal)

This specimen needs to be rehydrated/relaxed in order to remove some distracting debris and reposition the legs for better photo poses.

No. 4 | Libellula incesta | exuvia (ventral)

To be continued…

The Backstory

A Slaty Skimmer dragonfly (Libellula incesta) nymph was collected by Bob Perkins on 29 May 2017 along Pine Creek in Carroll County, Virginia USA. The nymph was reared in captivity until it emerged on 29 June 2017 and metamorphosed into an adult male. This specimen is the exuvia from the nymph.

Copyright © 2018 Walter Sanford. All rights reserved.


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