Posts Tagged ‘female’

Test shots: Brachytron pratense exuvia (female)

December 10, 2018

As if it weren’t challenging enough to identify odonate exuviae from species native to the United States of America (where I live), I just started working with some specimens collected by a good friend during April 2018 in Vienna, Austria.

I decided to start with a specimen that I recognized immediately as a member of the Family Aeshnidae (Darners). Here’s the decision tree used to identify the family.

  • The specimen has a flat labium that doesn’t cover the face (not mask-like).
  • Antennae are thin and thread-like (not club-like, as in Gomphidae larvae/euviae).
  • Eyes are large relative to the size of the head.

One-off

The first photo is a “one-off,” that is, not a composite image. The focus point is on the face mask/head; the rest of the subject is in soft focus. I think this is a good way to draw the viewer’s eyes to a specific part of a photo, while adding a sense of depth.

Hairy Dragonfly (Brachytron pratense) | exuvia (face/head-dorsal)

Composite images

The next “photo” is a three-layer focus-stacked composite image: The focus point is on the face mask/head in the first photo; the thorax in the second photo; and the terminal appendages in the third photo. The entire body of the exuvia is acceptably in focus, including the legs.

Notice the unusual shape of the head. Head shape can be used to identify some species in Family Aeshnidae. Source Credit: Sue Gregoire, personal communication. Kestrel Haven Migration Observatory.

In fact, several members of the “Dragonflies and Damselflies – Worldwide Odonata” Facebook group were able to identify this specimen based upon the shape of its head and eyes. Sincere thanks to Tim Termaat, Hartwig Stobbe, and Rob Strik for kindly identifying this specimen as an exuvia from a Hairy Dragonfly (Brachytron pratense), also known as a Hairy Hawker.

Hairy Dragonfly (Brachytron pratense) | exuvia (dorsal-lateral)

The last “photo” is a four-layer focus-stacked composite image: The focus point is on the head in the first and second photos; the thorax in the third photo; and the terminal appendages in the fourth photo. The entire body of the exuvia is acceptably in focus, including the legs.

This individual is a female, as indicated by the rudimentary ovipositor that can be seen clearly on the ventral side of abdominal segment nine (S9).

Hairy Dragonfly (Brachytron pratense) | exuvia (ventral)

Related Resources

Tech Tips

The following equipment was used to shoot both of the preceding photographs: 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); and Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and several external flashes set for “Slave” mode including Canon 580 EX- and Canon 580EX II Speedlites and a Godox TT685C Thinklite TTL Flash fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier.

Adobe Photoshop CC 2017 was used to create the two focus-stacked composite images, as well as spot-heal and sharpen all three images.

Copyright © 2018 Walter Sanford. All rights reserved.

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Do-over

October 24, 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 focus-stacked composite image was created from 39 photos focused on the face and head of the exuvia. I had relatively little experience using Adobe Photoshop to make focus stacks when I created the first iterations of the Ashy Clubtail composite image. I was never satisfied completely with the final output, so I decided to do a do-over.

After…

The updated version of the composite image was created using my “Latest focus stacking workflow.”

Before…

The version that I published in late-March 2018 was created using the RAW photos (CR2) from my Canon digital camera, without any post-processing. I tried to adjust the white balance and color palette of the resulting composite image, but was unable to get the “look” I wanted. The image is probably over-sharpened too.

Which version do you prefer?

I know the version I like more. Which do you prefer, After or Before?

Tech Tips

The preceding images are composites 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.

Field marks for identification of S. rogersi

October 22, 2018

The following annotated images illustrate field marks that can be used for identification of Sable Clubtail dragonfly (Stenogomphurus rogersi). Although there is some redundancy among the images, repetition is a good strategy for learning.

Male

Male Sable Clubtails have eyes that are green to turquoise in color, with a black occiput located between the eyes. They have a thin, black abdomen that flares to a small club featuring thin yellow flanges on abdominal segments seven through nine (S7-9).

The abdomen is marked with small pale dorsal triangles (S3-7) and tiny pale lateral spots. The number of dorsal triangles can vary individually and/or geographically, ranging from S3-5 to S3-7.

08 JUN 2018 | Fairfax County, VA | Sable Clubtail (male)

Dennis Paulson, originator of the classification system for thoracic stripes in the Family Gomphidae (Clubtails), describes T1-4 as follows.

T1–2 broad and complete, touching at ends and often with stripe between them restricted and topped with spot; T3–4 fine, T3 incomplete. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 6089-6093). Princeton University Press. Kindle Edition.

Note: T1-4 refers to the dark areas located on the sides of the thorax, not the lighter colored lines and spots. Due to space limitations, thoracic stripes are labeled using a numeral only (e.g., “1”) rather than a letter and numeral (e.g., “T1”).

08 JUN 2018 | Fairfax County, VA | Sable Clubtail (male)

Their face is pale, marked with variable black crosslines (as shown in the inset photo, below).

08 JUN 2018 | Fairfax County, VA | Sable Clubtail (male)

Male Sable Clubtails, like all male dragonflies, have three terminal appendages, collectively called “claspers.” All male clubtail dragonflies have indented hind wings.

Female

Female Sable Clubtails have a noticeably thicker abdomen than males. The occiput is a pale color, rather than black. Dorsal triangles, located on abdominal segments three through seven (S3-7), are much larger than those found on males. The lateral spots are somewhat larger as well.

05 JUL 2018 | Fairfax County, VA | Sable Clubtail (female)

Female Sable Clubtails, like all female dragonflies, have a pair of cerci (superior appendages) that have little or no function. All female clubtail dragonflies have rounded hind wings.

Related Resource: Stenogomphurus rogersi exuvia.

Copyright © 2018 Walter Sanford. All rights reserved.

Unicorn Clubtail (female terminal appendages)

September 22, 2018

Two field markers can be used to identify female Unicorn Clubtail dragonflies (Arigomphus villosipes), as shown in the following annotated image: 1) they have two terminal appendages (cerci) rather than three (males); and 2) their hind wings are rounded rather than “indented” (males).

Image used with permission from Bob Blakney.

Editor’s Notes

In my experience, female Unicorn Clubtail dragonflies are seen uncommonly. Sincere thanks to Bob Blakney for kindly granting permission to use his excellent photograph of this uncommon beauty for instructional purposes.

Bob’s photo was taken on 18 May 2012 at Occoquan Bay National Wildlife Refuge using a Canon EOS Rebel T2i digital camera and Tamron AF 18-270mm macro lens.

Copyright © 2018 Walter Sanford. All rights reserved.

Gray Petaltail (female terminal appendages)

September 18, 2018

For those species of dragonflies that do not display sexual dimorphism, males and females are nearly identical in appearance except for their terminal appendages. For example, male and female Gray Petaltail dragonflies (Tachopteryx thoreyi) are similar in appearance.

Two field markers can be used to identify female Gray Petaltails, as shown in the following annotated images: 1) they have two terminal appendages (cerci) rather than three (males); and 2) their hind wings are rounded rather than “indented” (males).

30 MAY 2018 | Northern Virginia | Gray Petaltail (female)

Female dragonflies have a pair of cerci (superior appendages) that have little or no function.

30 MAY 2018 | Northern Virginia | Gray Petaltail (female)

Related Resources

Copyright © 2018 Walter Sanford. All rights reserved.

Blue Dasher dragonfly (female)

August 23, 2018

A Blue Dasher dragonfly (Pachydiplax longipennis) was spotted during a photowalk at Occoquan Regional Park, Fairfax County, Virginia USA. This individual is a female, as indicated by her coloration and terminal appendages.

This camera-shy girl was hiding her face from me behind the thin veil of her left forewing.

Copyright © 2018 Walter Sanford. All rights reserved.

Calico Pennant dragonfly (female)

August 13, 2018

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

10 AUG 2018 | Occoquan Bay NWR | Calico Pennant (female)

This individual is a female, as indicated by her terminal appendages.

Adult flight period

The adult flight period  for Calico Pennant is from 11 May to 23 September (peaks in June-July), according to records for Northern Virginia maintained by Kevin Munroe, former manager at Huntley Meadows Park. In my experience, mid-August is past peak in Northern Virginia so I was happy to see a beautiful Calico female.

According to records for the Commonwealth of Virginia maintained by Dr. Steve Roble, a zoologist at the Virginia Department of Conservation and Recreation, Division of Natural Heritage, 26 April to 27 October is the adult flight period for Calico Pennant.

Copyright © 2018 Walter Sanford. All rights reserved.

Blue-fronted Dancer damselflies (male, females)

August 7, 2018

Several Blue-fronted Dancer damselflies (Argia apicalis) were photographed along an unnamed small creek in Fairfax County, Virginia USA.

Male

The first individual is a male, as indicated by the pattern of coloration on his thorax and abdomen.

06 AUG 2018 | Fairfax County, VA | Blue-fronted Dancer (male)

Female

Female A. apicalis is polymorphic, including two morphs: tan; and blue.

06 AUG 2018 | Fairfax County, VA | Blue-fronted Dancer (female, tan)

Blue females can be differentiated from blue males by looking for the reproductive anatomy located on the underside of the posterior end of their abdomen.

06 AUG 2018 | Fairfax County, VA | Blue-fronted Dancer (female, blue)

Copyright © 2018 Walter Sanford. All rights reserved.

Black-shouldered Spinyleg (female)

July 24, 2018

A Black-shouldered Spinyleg dragonfly (Dromogomphus spinosus) was spotted along an unnamed small creek in Fairfax County, Virginia USA. This individual is a female, as indicated by her terminal appendages.

19 JUl 2018 | Fairfax County, VA | Black-shouldered Spinyleg (female)

The tip of the dragonfly’s right hind wing appears to be slightly malformed; her ability to fly didn’t seem to be impaired by the malformation.

Look at the full-size version of the following photo. Notice the fuzzy schmutz on her face and legs. I speculate the dragonfly might have enjoyed either a butterfly or moth for her last meal.

19 JUl 2018 | Fairfax County, VA | Black-shouldered Spinyleg (female)

Copyright © 2018 Walter Sanford. All rights reserved.

Damnselflies

July 22, 2018

Did you notice what I did there? It’s not that I don’t like damselflies. I do. They don’t like me. I’m comfortable identifying some members of two of the three families of damselflies that occur in the mid-Atlantic states (USA), including Family Calopterygidae (Broad-winged Damselflies) and Family Lestidae (Spreadwings). Most members of the Family Coenagrionidae (Narrow-winged Damselflies), not so much.

I remember clearly the time when I was learning to identify dragonflies. I was more than a little confused at first. With persistence, the puzzle pieces started to fall into place sooner than I expected. Same story when I started learning to identify odonate exuviae. Never happened with damselflies, for whatever reason.

For example, here’s a photograph of a damselfly that I photographed recently at an unnamed small creek in Fairfax County, Virginia USA. I made a tentative identification after I edited the photo — I misidentified both the species and gender as an immature male Powdered Dancer damselfly (Argia moesta).

19 JUL 2018 | Fairfax County, VA | Blue-fronted Dancer (female)

As it turns out, this individual is a female Blue-fronted Dancer damselfly (Argia apicalis). Sincere thanks to my good friend Mike Boatwright, administrator of the Virginia Odonata Facebook group, for correcting my misidentification!

Copyright © 2018 Walter Sanford. All rights reserved.

 


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