Posts Tagged ‘Potomac River’

Swift River Cruiser exuvia

April 25, 2018

A late-stage emergent teneral female Swift River Cruiser dragonfly (Macromia illinoiensis) was spotted on 27 May 2017 along the Potomac River at Riverbend Park in Fairfax County, Virginia USA. The exuvia was collected, with permission from park staff, after the female flew away from the place where she metamorphosed from a nymph to an adult.

No. 1 | 27 MAY 2017 | Riverbend Park | Swift River Cruiser (female)

The next image is a composite of 35 photos. The specimen is perfectly in focus from head-to-tail, including the legs.

The last image is a composite of eight photos. The focus point for each photo in the set is limited to the body only. Surprisingly, all six legs are acceptably in focus except for the tip of the left hind leg.

The official early-date for Swift River Cruiser dragonfly is 08 May in the Commonwealth of Virginia. Since the early-date for Royal River Cruiser dragonfly (Macromia taeniolata) is 15 May, the exuvia helps to confirm the identity of the adult is Swift River Cruiser. 10 October is the late-date for both species.

Tech Tips

Photo No. 1 was taken using my Panasonic Lumix DMC-FZ150 superzoom bridge camera plus Canon 580EX Speedlite, my go-to kit for photowalking.

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. 2-3 are focus-stacked composite images created using Adobe Photoshop CC 2017.

Related Resource: Swift River Cruiser (emergent female).

Copyright © 2018 Walter Sanford. All rights reserved.

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Before and after

March 6, 2018

A recent blog post entitled Getting Started features photos of four odonate exuviae collected by Michael Powell during a photowalk along the Potomac River in Fairfax County, Virginia USA.

Before

The first photograph is one of several quick-and-dirty shots I took of one of the exuviae, without removing it from the small plastic tub in which it is stored. As you can see, the specimen appears to be in poor condition. Well, appearance can be deceiving, as they say.

No. 1 | Potomac River, Fairfax County, VA | Zygoptera exuvia

After

The last photograph shows the same exuvia after soaking in a bath of soapy water for at least 24 hours. When the specimen was pliable, it could be re-posed and allowed to dry/harden for another 24 hours.

No. 2 | Potomac River, Fairfax County, VA | Zygoptera exuvia

The exuvia is missing a set wing pads and the abdomen is still dented/twisted. That being said, most people would agree the specimen looks much better. More importantly, it’s easier to see the anatomy of the exuvia.

Taxonomic classification

This individual is a member of the Family Coenagrionidae (Narrow-winged Damselflies) as indicated by its keystone-shaped prementum, shown in Photo No. 1. The next challenge is to identify its genus and species.

Copyright © 2018 Walter Sanford. All rights reserved.

Head-to-head

March 4, 2018

Head shots of an odonate exuvia from a Russet-tipped Clubtail dragonfly (Stylurus plagiatus) were taken using two macro lenses: Canon EF100mm f/2.8L Macro lens (smallest aperture = f/32); Canon MP-E 65mm Macro lens (smallest aperture = f/16).

No. 1 | Canon EF 100mm Macro lens | f/22

Although there is more depth of field at f/22 than f/11, the more dramatic shot appears to be the one taken at higher magnification using the Canon MP-E 65mm Macro lens (shown below). Which photo do you prefer?

No. 2 | Canon MP-E 65mm Macro lens | f/11

Tech Tips

The following equipment was used to shoot Photo No. 1: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tube; Canon EF100mm f/2.8L Macro lens (set for manual focus, ~1x magnification); and Canon MT-26EX-RT Macro Twin Lite.

Photo No. 2: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification); and Canon MT-26EX-RT Macro Twin Lite.

Sunpak LED-160 Video Light (with a white translucent plastic filter) was used for both photos.

Related Resource: Stylurus plagiatus exuvia.

Copyright © 2018 Walter Sanford. All rights reserved.

Stylurus plagiatus exuvia

March 2, 2018

Michael Powell collected several odonate exuviae during a photowalk along the Potomac River in Fairfax County, Virginia USA, including two damselflies and two dragonflies. The exact date is uncertain, although Mike thinks the exuviae were collected sometime between 19-23 July 2017.

Both dragonfly exuviae are from the Family Gomphidae (Clubtails), as indicated by a flat labium that doesn’t cover the face as well as club-like antennae. The smaller specimen was identified as an Erpetogomphus designatus exuvia; this post describes the decision tree used to identify the larger specimen.

No. 1 | Stylurus plagiatus | exuvia (face-head)

Refer to Photo No. 2, 3, and 4. Notice that abdominal segment nine (S9) is elongated, strongly suggesting this individual is a member of the genus Stylurus.

The dichotomous key for Stylurus larvae that appears on pp. 310-312 in Dragonflies of North America, Third Edition by Needham et al. was used to identify the species of the exuvia. The ninth couplet [9, 9′] is as follows.

9(7’). Length of abdominal segment 9 at least equal to its basal width; lateral spines of abdominal segment 9 at least 1-1/2 times as long as those of segment 8; dorsal hook of segment 9 often large, in southern specimens overhanging segment 10; each labial palp with 3 teeth in addition to end hook; greatest width of prementum at least 4/5 its length. [plagiatus]
9’. Length of abdominal segment 9 less than its basal width; lateral spines of abdominal segment 9 no more than 1-1/2 times as long as those of segment 8; dorsal hook of segment 9 small, sometimes vestigial; labial palp with 2-3 teeth in addition to end hook; greatest width of prementum no more than 3/4 its length. [10]

Abdominal segment nine (S9) is slightly longer than its basal width, as shown in Photo No. 2. The lateral spines of segment nine (S9) are much longer than segment eight (S8).

No. 2 | Stylurus plagiatus | exuvia (dorsal)

Photo No. 3 shows a dorsal view of the distal abdomen. Notice the large dorsal hook of abdominal segment nine (S9) overhangs segment 10 (S10), a key marker for southern specimens of plagiatus. The dorsal hook couldn’t be seen before the exuvia was cleaned.

No. 3 | Stylurus plagiatus | exuvia (dorsal)

The flat labium doesn’t cover the face, as shown in Photo No. 4 and 5.

No. 4 | Stylurus plagiatus | exuvia (ventral)

Photo No. 5 shows a close-up of the prementum. Each labial palp features at least three (3) teeth in addition to the end hook. The greatest width of the prementum is approximately four-fifths (4/5) of its length.

No. 5 | Stylurus plagiatus | exuvia (prementum)

This specimen is confirmed as an exuvia from a Russet-tipped Clubtail dragonfly (Stylurus plagiatus).

The Backstory

Photo No. 6, featured in a recent blog post entitled Getting Started, is focused on abdominal segment nine (S9).

This specimen may need to be cleaned in order to see more clearly some key field markers used for identification.

No. 6 | Potomac River, Fairfax County, VA | odonate exuvia

The specimen was soaked in soapy water for at least 24 hours. A plastic spoon was used to scoop the exuvia from the water bath and transfer it to a dry plastic tray. Then a soft artist’s paintbrush was used to clean the exuvia, with extra attention on abdominal segment nine (S9). Two damselfly exuviae are soaking in the same water bath, shown below. Other useful tools include a magnifying glass and a plastic toothpick.

The odonate exuviae cleaning station at BoG Photo Studio.

The exuvia is pliable after soaking in water for at least 24 hours. After the specimen was cleaned, it was posed and allowed to dry for another day. The handle of a plastic spoon is a good drying rack that makes it easier to pose the legs. The Stylurus plagiatus exuvia is shown in the following photograph. The broken leg resting on the handle of the spoon was attached to the body only by spider web.

Stylurus plagiatus exuvia, posed on the handle of a plastic spoon.

Tech Tips

The following equipment was used to shoot Photo No. 1, 2 and 4: 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 LitePhoto No. 3 and 5: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification); and Canon MT-26EX-RT Macro Twin Lite. A Sunpak LED-160 Video Light (with a white translucent plastic filter) was used for some photos.

A Panasonic Lumix DMC-FZ150 superzoom bridge camera was used to take photos of the odonate exuviae cleaning station.

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resources

Copyright © 2018 Walter Sanford. All rights reserved.

Erpetogomphus designatus exuvia

February 28, 2018

Michael Powell collected several odonate exuviae during a photowalk along the Potomac River in Fairfax County, Virginia USA, including two damselflies and two dragonflies. The exact date is uncertain, although Mike thinks the exuviae were collected sometime between 19-23 July 2017.

A two-step process was used to identify the genus and species of one of the two dragonfly exuviae.

  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). [See Photo No. 4.]
  • Antennae are club-like (not thin and thread-like, as in Aeshnidae). [See Photo No. 1.]
  • Eyes not exceptionally large compared to the size of the head (not large, as in Aeshnidae). [See Photo No. 1.]
(See a full-size version of the original photo, without annotation.)

Step 2. Genus and species

The dichotomous key for Erpetogomphus larvae that appears on pp. 156-157 in Dragonflies of North America, Third Edition by Needham et al. was used to identify the genus and species of the exuvia. The first couplet [1, 1′] is as follows.

1. Dorsal hooks well-developed on abdominal segments 2-9 (Fig. 183a) [2]
1’. Dorsal hooks absent or vestigial on abdominal segments 7-9 (Fig. 183c) (usually present on at least some of the more anterior segments [3]

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

A leap of faith is required to see the small dorsal hooks present on abdominal segments two through nine (S2 – S9), but they are there.

Notice the divergent wing pads. The white filaments that extend from the split in the thorax (as shown above) are breathing tubes, artifacts of the unique respiratory system of dragonfly nymphs.

2(1). Lateral spines present on abdominal segments 6-9 only; femora with long, hair-like setae [designatus] [Eastern Ringtail]
2’. Lateral spines present on abdominal segments 5-9 only; femora without long, hair-like setae [constrictor] [Knob-tipped Ringtail]

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

The caudal appendages (terminal appendages) are all about the same length, a key marker for designatus.

Notice the flat labium that doesn’t cover the face, as shown in the following photo.

This specimen is tentatively identified as an exuvia from an Eastern Ringtail dragonfly (Erpetogomphus designatus). The exuvia that Mike Powell collected is similar in appearance to the following excellent photograph of an Erpetogomphus designatus nymph by Steve Krotzer, Haysop Hill Photography.

Image used with permission from Steve Krotzer.

Tech Tips

The following equipment was used to shoot Photo No. 2 and 4: 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 LitePhoto No. 1 and 3: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification); and Canon MT-26EX-RT Macro Twin Lite. A Sunpak LED-160 Video Light (with a white translucent plastic filter) was used for some photos.

Adobe Photoshop CC 2017 was used to annotate selected images.

Copyright © 2018 Walter Sanford. All rights reserved.

Getting started

February 26, 2018

Michael Powell, a good friend and fellow Northern Virginian, collected several odonate exuviae during a photowalk along the Potomac River in Fairfax County, Virginia USA.

The four exuviae that Mike collected are stored in one of those empty containers of Philadelphia cream cheese spread that I endorsed in a recent blog post. I shot several quick-and-dirty photographs of the exuviae, without removing them from the small plastic tub. Usually I wouldn’t publish photos of this quality. The photos are like a sketch pad that will be used to make a tentative plan for photographing the specimens and attempting to identify them to the genus and species level, if possible.

Spoiler Alert: If you can identify any of the exuviae featured in this post, then PLEASE DON’T TELL ME! I enjoy the challenge of solving the mystery of their identity. Thank you!

Dragonfly exuviae

Mike collected two dragonfly exuviae that are from the Family Gomphidae (Clubtails), as indicated by a flat labium that doesn’t cover the face as well as club-like antennae.

My working theory is the first specimen might be an exuvia from an Eastern Ringtail dragonfly (Erpetogomphus designatus).

Potomac River, Fairfax County, VA | odonate exuvia

Post Update: The identity of the first specimen is confirmed as an Erpetogomphus designatus exuvia.

The next exuvia appears to be a member of the genus Stylurus, possibly plagiatus (Russet-tipped Clubtail).

Potomac River, Fairfax County, VA | odonate exuvia

The preceding photo was focused on the head; the following photo was focused on abdominal segment nine (S9). This specimen may need to be cleaned in order to see more clearly some key field markers used for identification.

Potomac River, Fairfax County, VA | odonate exuvia

Post Update: The identity of the first specimen is confirmed as a Stylurus plagiatus exuvia.

Damselfly exuviae

It is relatively easy to identify damselflies (Suborder Zygoptera) to the family level based upon the shape of the prementum. Both damselfly exuviae that Mike collected are members of the Family Coenagrionidae (Narrow-winged Damselflies).

It is more challenging to identify damselfly specimens to the genus/species level. In this case, possible genera include Argia (Dancers), Enallagma (American Bluets), and Ischnura (Forktails).

Potomac River, Fairfax County, VA | odonate exuvia

The last damselfly exuvia is smaller than the first. It will need to be soaked in soapy water for at least 24 hours in order to make the specimen pliable so it can be re-posed before it is photographed.

Potomac River, Fairfax County, VA | odonate exuvia

Copyright © 2018 Walter Sanford. All rights reserved.

Cobra Clubtail dragonflies (females)

December 6, 2017

Male and female Cobra Clubtail dragonflies (Gomphurus vastus) are nearly identical in appearance except for their terminal appendages: females have two terminal appendages (cerci); males have three (claspers). Also notice the subtle difference in the shape of their hind wings: female hind wings are rounded; male hind wings are “indented.”

Several female Cobra Clubtails were photographed during the annual mass emergence along the Potomac River at Riverbend Park, Fairfax County, Virginia USA.

The first female, shown above, has a malformed wing.

Notice part of an insect leg on the wooden beam, underneath the female’s abdomen. Is it a leftover from a late-morning snack?

Copyright © 2017 Walter Sanford. All rights reserved.

Incredible!

December 4, 2017

Odonates are aquatic insects. They spend most of their life as larvae that live in water; this stage of their life cycle can last from a few months to a few years. Finally, they emerge from the water and metamorphose into adults in order to reproduce; their offspring return to the water and the cycle begins again.

Careful and/or lucky observers will notice exuviae (sing. exuvia), also known as either “cast skins” or “shed skins,” left behind when odonate larvae emerge. Would you believe this…

metamorphosed into that? (See below.) It’s a miraculous transformation! The adult stage of the odonate life cycle can last from a week-or-so to a month-or-so, depending upon the species.

The first photo shows an exuvia from a Cobra Clubtail dragonfly (Gomphurus vastus), photographed in situ at Riverbend Park, Fairfax County, Virginia USA. All other photos in this gallery show adult male Cobra Clubtails, as indicated by their terminal appendages and “indented” hind wings.

Copyright © 2017 Walter Sanford. All rights reserved.

Reminiscing

December 2, 2017

As I was reminiscing about the annual mass emergence of Cobra Clubtail dragonflies (Gomphurus vastus) along the Potomac River at Riverbend Park, Fairfax County, Virginia USA, I realized there are lots of photos shot in May 2017 that were never edited.

This photo set features a female perching on colorful kayaks in a storage rack near the boat ramp. Both photos are uncropped, that is, they are full-size images (4,000 x 3,000 pixels).

Related Resource: Because it’s fun, a blog post featuring photos of a male Cobra Clubtail (perching on the same kayaks) shot on the same day using my Fujifilm X-T1 digital camera.

Copyright © 2017 Walter Sanford. All rights reserved.

Exuviart

August 22, 2017

Regular readers of my blog remember when I coined the term “Odonart” and created an “Odonart Portfolio.”

I just coined a new term: “Exuviart.” Exuviart is a concatenation of two words: exuvia; and art. The following photographs are the first additions to the Exuviart wing of my Odonart Portfolio.


Unpublished Photo

An Eastern Amberwing dragonfly (Perithemis tenera) exuvia, from the Family Libellulidae (Skimmers), was collected from the Potomac River in Fairfax County, Virginia USA.

Whenever possible, I like to collect exuviae along with some of the vegetation that was the site for emergence. The vegetation helps to show scale. In this case, the small specimen is approximately 1.4 cm (~0.6″) in length and approximately 0.6 cm (~0.2″) in maximum width. I like the way the desiccated leaf retained its color and gained a velvety texture.

Tech Tips

The following equipment was used to shoot the preceding photograph: Canon EOS 5D Mark II DSLR; Canon EF100mm f/2.8 Macro lens plus Raynox DCR-250 close-up filter; Canon 580EX II Speedlite; Canon 580EX Speedlite; and a coiled six-foot Vello Off-Camera TTL Flash Cord for Canon Cameras. The specimen was staged on a piece of white plastic (12″ square, matte finish).


Published Photos

A Common Green Darner dragonfly (Anax junius) exuvia, from the Family Aeshnidae (Darners), was collected at Hidden Pond, Meadowood Recreation Area (MRA), Fairfax County, Virginia USA.

Tech Tips

The following equipment was used to shoot the preceding photograph: Canon EOS 5D Mark II digital camera, in manual mode; Canon EF100mm f/2.8L Macro lens (set for manual focus); Canon 580EX II external flash, off-camera, in manual mode; Canon 580EX external flash, off-camera, in manual mode; and a Yongnuo YN-622C-TX E-TTL II Wireless Flash Controller for Canon plus a two-pack of Yongnuo YN-622C II E-TTL Wireless Flash Transceivers for Canon.


A Cobra Clubtail dragonfly (Gomphurus vastus) exuvia, from the Family Gomphidae (Clubtails), was collected at Riverbend Park with permission from park staff.

Tech Tips

The following equipment was used to shoot the preceding photograph: 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 and Raynox DCR-250 close-up filter; Canon 580EX II external flash, off-camera, in manual mode; Canon 580EX external flash, off-camera, in manual mode; and a Yongnuo YN-622C-TX E-TTL II Wireless Flash Controller for Canon plus a two-pack of Yongnuo YN-622C II E-TTL Wireless Flash Transceivers for Canon.

Copyright © 2017 Walter Sanford. All rights reserved.


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