Archive for the ‘dragonflies’ Category

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.

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Gray Petaltail (male terminal appendages)

September 20, 2018

“Bender,” my nickname for a male Gray Petaltail dragonfly (Tachopteryx thoreyi) with a malformed abdomen, is featured in the following set of annotated photos.

06 JUN 2018 | Northern Virginia | Gray Petaltail (male)

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”).

Gray Petaltail males have “indented” hind wings, as shown in the last photo.

06 JUN 2018 | Northern Virginia | Gray Petaltail (male)

Related Resources

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.

Studio macro photography rig

September 12, 2018

This blog post features a couple of quick-and-dirty photos that provide a behind-the-scenes look at some of the photography gear I use for studio macro photography.

The following equipment is shown in the first photo, taken using an iPad mini (with retina display): 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.

The Canon DSLR is mounted on a Neewer Pro 4-Way Macro Focusing Rail Slider using a Manfrotto quick-release plate. Although the quick-release plate isn’t essential gear, it makes set-up and tear-down easy and fast. The focusing rails are mounted on a Manfrotto 405 Pro Digital Geared Head, connected to a Manfrotto 055XPROB Pro Tripod [discontinued].

Photography gear used for studio macro photography.

A Canon 580EX II Speedlite is mounted on a Manfrotto 054 Magnesium Ball Head with Q2 Quick Release [discontinued], connected to a Vanguard Alta Pro 263AB 100 Aluminum Alloy Tripod. A Canon 580EX Speedlite is mounted on a Sunpak 8001 UT medium duty aluminum tripod.

The last photo, taken using a Panansonic Lumix DMC-FZ150 superzoom bridge camera, shows the “stage” used for posing subjects such as the Zebra Clubtail dragonfly (Stylurus scudderi) exuvia shown in the preceding photo. A Tether Tools “Rock Solid Master Articulating Arm & Clamp Kit” connects one end of the articulating arm to a leg of the Manfrotto tripod; a Manfrotto 2909 Super Clamp is connected to the other end of the articulating arm and used to hold a piece of opaque white plastic that is 12″ square. (Yep, that’s a folded paper towel used to prevent the clamp from scratching the plastic.) The plastic has a smooth side and a textured side; I prefer the textured side. An Opteka Triple Axis Spirit Level is used to level the “stage.”

Macro photography “stage.”

Product Reviews

See “Good news, bad news,” a related blog post in which I reviewed the Manfrotto 405 geared tripod head and Neewer focus rails.

Manfrotto makes an articulating arm that is similar to the one made by Tether Tools, shown above. The Manfrotto 244N Variable Friction Magic Arm is more expensive than the Tether Tools “Rock Solid Master Articulating Arm,” so I chose the less expensive arm. I’m reminded of the old saying “you get what you pay for.” In retrospect, I don’t recommend any of the articulating arms and clamps made by Tether Tools.

Copyright © 2018 Walter Sanford. All rights reserved.

Epitheca princeps exuvia

September 6, 2018

An odonate exuvia was collected by Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, on 07 June 2018 at Otter Lake in Amherst County, Virginia USA.

A two-step process was used to identify the genus and species of the specimen.

  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 Corduliidae (Emeralds).

  • The specimen has a mask-like labium (prementum) that covers the face, as shown in Image No. 1, characteristic of four families of odonates: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).
  • There is no horn on 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: It’s probably Corduliidae if the cerci are at least half as long as the paraprocts, as shown in Image No. 4. [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).

No. 1Epitheca princeps | exuvia (face-head)

Step 2. Genus and species

Characters from two dichotomous keys were used to identify the genus and species: Prince Baskettail dragonfly (Epitheca princeps). See Epitheca princeps exuvia, another of my illustrated guides to identification of odonate exuviae, for a detailed explanation of the decision tree used to identify the genus and species of this specimen.

No. 2 | Epitheca princeps | exuvia (dorsal)

This individual is a male, as indicated by the vestigial hamuli visible on the ventral side of abdominal segments two and three (S2-3).

No. 3Epitheca princeps | exuvia (ventral)

Notice the cerci are at least half as long as the paraprocts, as shown in Image No. 4.

No. 4Epitheca princeps | exuvia (posterior abdomen)

Image No. 5 shows a dorsal-lateral view of the mid-dorsal hooks.

No. 5Epitheca princeps | exuvia (dorsal-lateral)

Look-alike species

I really wanted this specimen to be Stream Cruiser dragonfly (Didymops transversa). I think exuviae from D. transversa and E. princeps are similar in appearance — an opinion not shared by at least one expert on identification of odonate exuviae.

Two characters proved to be the deal-breaker that forced me to abandon D. tranversa in favor of E. princeps. 1) The specimen does not have a horn on its face-head. 2) This specimen is only 25 mm long (2.5 cm); D. transversa larvae/exuviae are 30 mm long (3.0 cm), according to Dragonflies of North America, Needham, James G., et al.

Tech Tips

The following equipment was used to shoot Image No. 1-5: 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.

Image No. 1-5 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017: Image No. 1 (7 photos); Image No. 2 (22 photos); Image No. 3 (19 photos); Image No. 4 (10 photos); Image No. 5 (20 photos).

Copyright © 2018 Walter Sanford. All rights reserved.

Stylurus sp. exuvia

August 25, 2018

Two similar odonate exuviae were collected by Michael Boatwright on 11- and 13 July 2018 along a medium-size stream in Amherst County, Virginia USA. Mike and I collaborated to identify the specimen collected on 13 July.

A two-step process was used to identify the genus and species 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 (prementum) that doesn’t cover the face (not mask-like), as shown in Image No. 1, 3-5.
  • Antennae are club-like (not thin and thread-like, as in Aeshnidae larvae), as shown in Image No. 1.
  • Eyes not exceptionally large compared to the size of the head (not large, as in Aeshnidae), as shown in Image No. 1.

It’s relatively simple and straightforward to recognize this specimen is a clubtail. Determination of the genus and species is more challenging.

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

Step 2. Genus and species

Several dichotomous keys were used to determine the genus and species of the exuvia. (See Related Resources.) By far the easiest keys to use are found in Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz. Markers that match this specimen are highlighted in boldface green text. Three boldface green asterisks (***) are used to highlight the thread for identification of this specimen.

p. 7 – Key to the Genera of the Family Gomphidae

p. 9
***8a. Tibial burrowing hooks vestigial or lacking; 1-4 palpal teeth [see Image No. 5]; abdomen slender, no wider than head [see Image No. 2]. [Stylurus]

p. 16
[diagrams (showing palpal lobe)] … traced from Walker (1928)

This specimen is a species from the genus Stylurus, confirmed by Kenneth J. Tennessen, Ph.D. in Entomology (personal communication).

p. 17 – Key to the Species of the Genus Stylurus

***1b. Abdominal segment 9 less than twice as long as wide at base [see Image No. 2]. [2]

2a. Vestigial dorsal hook, represented on segment 9 by small flattened triangular rearward projection on mid-dorsal line, not hooklike in form. [3]
***2b. Nothing representing a hook on 9. [4]

3a. … [notatus] ← Elusive Clubtail
3b. … [plagiatus] ← Russet-tipped Clubtail

4a. Total length less than 34 mm; median lobe of labium very convex. [amnicola] ← Riverine Clubtail
***4b. Total length more than 34 mm [see Image No. 2]; median lobe of labium only slightly convex [see Image No. 5]. [scudderi] ← Zebra Clubtail

Note: See Walker (1928) for a complete description of the nymphs of Stylurus.

[diagrams (showing posterior abdomen)] … traced from Walker (1928)

The exuvia is ~37 mm (~3.7 cm) long, measured from end-to-end, including the antennae that extend ~1-2 mm in front of the face. The overall shape of the posterior abdomen most closely matches S. scudderi, as shown by tracings in the Soltesz key. The length of abdominal segment nine (S9) is less than its basal width. S9 is only slightly longer than S8. S10 is wider than its length.

No. 2 | Stylurus sp. | exuvia (dorsal)

Notice the flat labium (prementum) doesn’t cover the face of the specimen, as shown in Image No. 1, 3-5. The basal width of the lateral spine on abdominal segment nine (S9) in lateral view is approximately equal to the basal width of the spine in dorsal view.

No. 3 | Stylurus sp. | exuvia (lateral)

The lateral spine on abdominal segment nine (S9) is nearly as long as abdominal segment 10 (S10).

No. 4 | Stylurus sp. | exuvia (ventral)

The overall shape of the palpal lobes most closely matches S. scudderi, as shown by tracings in the Soltesz key. Note the median lobe of the labium (prementum) is only slightly convex, as shown by both the tracings and Image No. 5.

No. 5 | Stylurus sp. | exuvia (prementum)

What it is

According to the identification key for the genus Stylurus compiled by Ken Soltesz, this specimen is Zebra Clubtail (Stylurus scudderi).

Soltesz’s key is based, in part, on the excellent work of E. M. Walker in 1928. (See Related Resources.) Neither Walker’s paper nor Soltesz’s identification key includes Laura’s Clubtail (Stylurus laurae), described in 1932 (Benjamin Coulter, personal communication). There is considerable overlap in the characters used to identify S. laurae and S. scudderi that cannot be ignored.

We referred to two more identification keys, one of which is known to contain misinformation in the keys for S. laurae and S. scudderi (Kenneth J. Tennessen, personal communication) — if one is flawed, then so is the other since both keys refer to many of the same characters. That being said, the greatest number of matching characters indicates S. scudderi although S. laurae cannot be 100% ruled out.

Further evidence

One of the two virtually identical odonate exuviae that Mike Boatwright collected included a teneral adult that failed to emerge successfully.

After careful examination, Mike tentatively identified the adult as a male Zebra Clubtail (Stylurus scudderi) based on the following characteristics.

Face yellow with crossbars forming a dark “X” with a light center. Front half of frons yellowish; rear of frons and vertex dark. Top of thorax dark brown with two vertical yellowish white stripes, and a light colored mid-dorsal stripe narrowing to a point at the yellowish-white collar stripe. Humeral and anti-humeral stripes (T1 and T2) dark brown and almost completely fused. Area between T2 and T3 a fairly broad yellow stripe. T3 and T4 dark brown, mostly fused, and bordered by light colored broad oval area below.

Abdomen slender with dark blackish-brown segments. Two pale yellow spots on the sides of S2 with one completely covering the auricle. Anterior end of S3-6 and posterior end of S9 with thin pale yellow to whitish ring. Lateral edges of S7-9 widely expanding forming a club with broad irregular whitish-yellow markings on lateral surfaces. Source Credit: Michael Boatwright.

Significance

Either Zebra Clubtail (S. scudderi) or Laura’s Clubtail (S. laurae) are new species of odonates for Amherst County, Virginia USA, as shown by the Dragonfly Society of the Americas species checklist for Amherst County.

Zebra Clubtail is not within range of Amherst County; Mike’s discovery could indicate expansion of its range farther eastward into Virginia. Laura’s Clubtail is within range of Amherst County, although unknown to occur there.

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, the adult flight period for Zebra Clubtail is 13 July to 02 October; Laura’s Clubtail is 20 June to 26 September.

Related Resources

Tech Tips

The following equipment was used to shoot Image No. 1-4: 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); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode. Image No. 5Canon MP-E 65mm Macro lens (manual focus only, set for ~2x magnification) plus the multiple-flash setup.

Image No. 1-5 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017: Image No. 1 (13 photos); Image No. 2 (14 photos); Image No. 3 (11 photos); Image No. 4 (18 photos); Image No. 5 (six photos).

Mike Boatwright’s photos, taken soon after the specimens were collected, were shot using a Samsung Model SM-G950U cell phone.

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.

Needham’s Skimmer dragonfly (female)

August 21, 2018

10 AUG 2018 | OBNWR | Needham’s Skimmer (mature female)

A Needham’s Skimmer dragonfly (Libellula needhami) was spotted during a brief photowalk at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. This individual is a mature female, as indicated by her terminal appendages, muted coloration, and slightly tattered wings.

Copyright © 2018 Walter Sanford. All rights reserved.

Stylurus sp. exuvia, ongoing work

August 17, 2018

The work to identify an unknown species of odonate exuvia continues. More focus-stacked composite images are in the pipeline to be published in one or more follow-up blog posts.

13 JUL 2018 | Amherst County, VA | Stylurus sp. exuvia (dorsal view)

Tech Tips

The preceding image is a composite of 21 photos taken using the following equipment: 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 in “Slave” mode.

Adobe Photoshop CC 2017 was used to create the composite image.

Related Resource: Stylurus sp. exuvia

Copyright © 2018 Walter Sanford. All rights reserved.

Stylurus sp. exuvia

August 15, 2018

The following image is a composite of 18 photos taken using the following equipment: 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 in “Slave” mode.

Adobe Photoshop CC 2017 was used to create the composite image.

13 JUL 2018 | Amherst County, VA | Stylurus sp. exuvia (ventral view)

The Backstory

I am collaborating with my good friend Mike Boatwright, administrator of the Virginia Odonata Facebook group, to identify an odonate exuvia that he collected on 13 July 2018 in Amherst County, Virginia USA. We know the exuvia is from the Family Gomphidae (Clubtails) and are fairly certain it is a species from the genus Stylurus. At this point, several species are still in play.

Sincere thanks to Benjamin Coulter for providing guidance and related resources as Mike and I work through several dichotomous keys for identification of Stylurus larvae.

Look for one or more follow-up blog posts as the work progresses.

Related Resource: Stylurus sp. exuvia, ongoing work

Copyright © 2018 Walter Sanford. All rights reserved.


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