Posts Tagged ‘Virginia’

You look like a tree to me!

May 22, 2019

Gray Petaltail dragonflies (Tachopteryx thoreyi) have a well-known preference for perching on gray or tan colored surfaces, including gray or tan colored clothing. Dressed appropriately, Mike Powell and I visited a hotspot for Gray Petaltail where we hoped to shoot some photographs of T. thoreyi perched on each other.

The first individual is a female, perched on the front of Mike Powell’s gray sweatshirt.

21 MAY 2019 | Northern Virginia | Gray Petaltail (female)

The last individual is a male, perched on Mike Powell’s left shoulder.

21 MAY 2019 | Northern Virginia | Gray Petaltail (male)

I’m guessing the dragonflies were thinking, “Hey Mike, you look like a tree to me!” No offense intended, good buddy. In fact, I think you should be flattered that these spectacular specimens befriended you!

Copyright © 2019 Walter Sanford. All rights reserved.

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Test shots: Aeshna umbrosa exuvia

December 3, 2018

Bob Perkins collected and reared an unknown species of odonate nymph from a tiny stream in Carroll County, Virginia USA. The larva emerged from one of Bob’s holding tanks overnight on 23-24 November 2018 and metamorphosed into an adult male Shadow Darner dragonfly (Aeshna umbrosa). Shadow Darner is a member of the Family Aeshnidae (Darners). The following test shots show the exuvia from the odonate nymph.

Test shots of this beautiful specimen were taken using a relatively small aperture of f/16 for greater depth of field. Each photo is a “one-off,” that is, not a composite image. Focus stacks will be created sometime in the near future, after the exuvia is rehydrated and its legs are repositioned  for easier posing.

Lateral-ventral view

The focus point of the first photo is on the right eye. Given the orientation of the specimen, most of the exuvia is acceptably in focus at f/16. For what it’s worth, I really like the composition of this photo!

Notice the specimen has a flat labium (prementum) that doesn’t cover the face (not mask-like). That is a characteristic field mark of two families of dragonflies: Family Aeshnidae (Darners); and Family Gomphidae (Clubtails).

Shadow Darner (Aeshna umbrosa) | exuvia (lateral-ventral)

This individual is a male, as indicated by vestigial hamules that are visible on the ventral side of the specimen.

Dorsal view

The focus point of the next photo is on the head: the head is tack-sharp; the terminal appendages are in soft-focus. Sometimes it’s necessary to create focus-stacked composite images in order to render the subject in focus from head-to-tail and edge-to-edge.

Lateral spines on abdominal segments six to nine (S6-9) indicate this specimen is A. umbrosa.

The focus point of the next photo is on the abdomen, just below the wing pads. Relative to the preceding photo, notice the head is slightly softer in focus while the terminal appendages are slightly sharper in focus.

Tech Tips

The following equipment was used to shoot all 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 spot-heal and sharpen all three images.

Copyright © 2018 Walter Sanford. All rights reserved.

Test shots: Tachopteryx thoreyi exuviae

November 30, 2018

Two Gray Petaltail dragonfly (Tachopteryx thoreyi) exuviae were collected on 23 May 2018 by Walter Sanford near a forested seep at an undisclosed location in Northern Virginia USA. Gray Petaltail is a member of the Family Petaluridae (Petaltails).

Although both specimens are similar, they aren’t identical. For example, twin rows of hook-like structures are clearly visible on the dorsal side of the abdomen on the lower exuvia, and almost invisible on the upper exuvia. The upper exuvia is dirtier and appears to be more “worn” than the lower one. Notice the “schmutz” on the face of the lower exuvia, probably a piece of leaf litter.

Both individuals might be male, as indicated by vestigial hamules that appear to be visible on the ventral side of the specimens.

Test shots of the specimens were taken using a relatively small aperture of f/16 for greater depth of field. Each photo is a “one-off,” that is, not a composite image. Focus stacks will be created sometime in the near future, after the exuviae are rehydrated, cleaned, and posed for better composition.

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 spot-heal and sharpen both images.

Copyright © 2018 Walter Sanford. All rights reserved.

Test shots: Stylurus sp. exuvia

November 23, 2018

Joe Johnston is an avid boater and sport fisherman who kindly agreed to be my “Eyes on the Aquia,” always on the lookout for odonate exuvia to share with me. On 18 July 2018, Joe collected an especially interesting specimen from Aquia Creek in Stafford County, Virginia USA.

Abdominal segment nine (S9) is elongated, strongly suggesting this individual is a member of the genus Stylurus (Hanging Clubtails).

Stylurus sp. | exuvia (dorsal)

Did you notice the spider carcass that photobombed my test shots of the exuvia? Look for the spider along the upper-edge of the thorax in the dorsal view; lower-edge in the ventral view.

Stylurus sp. | exuvia (ventral)

This individual might be Laura’s Clubtail (Stylurus laurae). Laura’s Clubtail is within range of Stafford County, although it is unknown to occur there. S. laurae would be a new species for the Dragonfly Society of the Americas Odonata Central species checklist for Stafford County, Virginia USA.

According to records for the Commonwealth of Virginia maintained by Dr. Steve Roble, Staff Zoologist at the Virginia Department of Conservation and Recreation, Division of Natural Heritage, the adult flight period for Laura’s Clubtail is 20 June to 26 September. The species is rare to uncommon. Its habitat is streams and rivers.

Tech Tips

The following equipment was used to shoot both of the macro photographs featured in this post: Fujifilm X-T1 digital camera; Fujifilm MCEX-11 extension tube; and Fujinon XF80mm macro lens plus lens hood. The camera was set for both manual exposure and manual focus. That’s right, a switch on the camera body is used to set the type of focus. It’s a Fujifilm thing. Actually, back-button focus was used to autofocus the image and adjusted manually as necessary. That’s also a Fujifilm thing. Camera settings: focal length 80mm (120mm, 35mm equivalent); f/16; 1/500s.

Godox XProF radio flash trigger, mounted on the hotshoe of my X-T1, was used to control a pair of off-camera Godox TT685 Thinklite TTL Flashes (TT685F and TT685C) set for radio slave mode. Each flash was fitted with a snap-on plastic diffuser.

Adobe Photoshop CC 2017 was used to spot-heal and sharpen both images.

Copyright © 2018 Walter Sanford. All rights reserved.

Test shots: Stylurus plagiatus exuvia

November 21, 2018

A Russet-tipped Clubtail (Stylurus plagiatus) exuvia was collected by Joe and Loren Johnston on 20 June 2018 from Aquia Creek in Stafford County, Virginia USA.

Notice that abdominal segment nine (S9) is elongated, strongly suggesting this individual is a member of the genus Stylurus. The large dorsal hook of abdominal segment nine (S9) that overhangs segment 10 (S10) is a key marker for southern specimens of plagiatus.

The “working distance” for the 11mm Fujifilm extension tube/Fujinon 80mm macro lens combo, that is, the distance from the front of the lens barrel to the subject, is long enough to be able to use the lens hood.

Hotspots from external flash units, technically known as specular highlights, are more noticeable sometimes when the flash heads are closer to the subject. It appears the lens hood may have reduced that problem; more experimentation is required to be sure.

Related Resource: Stylurus plagiatus exuvia, a photo-illustrated identification guide.

The Backstory

Joe Johnston is an avid boater and sport fisherman. On 20 June 2018, Joe and his brother Loren were fishing together on Aquia Creek in Stafford County, Virginia USA.

Fish require food and shelter. Sometimes fish shelter near trees that have fallen into water, or the wooden pilings of boat docks. Joe and Loren were casting artificial fishing lures toward one of several docks that extend far into Aquia Creek, when Loren’s lure snagged on one of the pilings. When Joe moved his boat alongside the piling in order to retrieve the fishing lure, Loren noticed an odonate exuvia on the side of the piling. Joe and Loren kindly collected several exuviae, including this one, and shared them with me. Thanks, gentlemen!

Tech Tips

The following equipment was used to shoot both of the macro photographs featured in this post: Fujifilm X-T1 digital camera; Fujifilm MCEX-11 extension tube; and Fujinon XF80mm macro lens plus lens hood. The camera was set for both manual exposure and manual focus. That’s right, a switch on the camera body is used to set the type of focus. It’s a Fujifilm thing. Actually, back-button focus was used to autofocus the image and adjusted manually as necessary. That’s also a Fujifilm thing. Camera settings: focal length 80mm (120mm, 35mm equivalent); f/16; 1/500s.

Godox XProF radio flash trigger, mounted on the hotshoe of my X-T1, was used to control a pair of off-camera Godox TT685 Thinklite TTL Flashes (TT685F and TT685C) set for radio slave mode. Each flash was fitted with a snap-on plastic diffuser.

Adobe Photoshop CC 2017 was used to spot-heal and sharpen both images.

Copyright © 2018 Walter Sanford. All rights reserved.

Macromia alleghaniensis exuvia

October 6, 2018

Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, collected an odonate exuvia on 07 June 2018 along either Little Otter Creek or Otter Creek near the place where both creeks are distributaries of Otter Lake in Amherst County, Virginia USA.

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 Macromiidae (Cruisers).

  • The specimen has a mask-like labium (prementum) that covers the face, as shown in Photo No. 1, characteristic of four families of odonates: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).
  • The teeth on the margins of the labium have a regular pattern. (The pattern reminds me of a “spork.”)
  • Its eyes are small, wide set, and stick up.
  • Image No. 2 shows there is a horn on the face-head, characteristic of Macromiidae.

Photo No. 1 shows a face-head view of the exuvia, magnified approximately three times life size (~3x).

No. 1 | Macromia alleghaniensis | exuvia (face-head)

Image No. 2 shows the top of the head of the exuvia, magnified approximately three times life size (~3x). Notice the prominent horn on the face.

No. 2 | Macromia alleghaniensis | exuvia (head-horn)

Step 2. Genus and species

Two dichotomous keys found on p. 27 of Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz, were used to determine 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 this specimen.

Key to the Genera of the Family Macromiidae

***1b. Lateral spines of abdominal segment 9 do not reach to rearward level of tips of inferior appendages [paraprocts]; Sides of head somewhat convergent behind eyes to pair of low turbercules on hind angles; Lateral setae of labium = 6; Small dorsal hook on segment 10. [Macromia]

A small dorsal hook on abdominal segment 10 is characteristic of Genus Macromia.

No. 3 | Macromia alleghaniensis | exuvia (dorsal-lateral)

Look closely at the full-size version of Image No. 4. Notice the little “nub” on abdominal segment 10 (S10), below the underside of the dorsal hook on abdominal segment nine (S9). The same structure is labeled with a white question mark in Image No. 3.

No. 4 | Macromia alleghaniensis | exuvia (dorsal-lateral)

The lateral spines of abdominal segment 9 (S9) do not reach rearward to the tips of the inferior appendages (paraprocts).

No. 5 | Macromia alleghaniensis | exuvia (dorsal)

Key to the Species of Macromia

1a. Lateral spines of abdominal segments 8 and 9 directed straight to rearward. [illinoiensis]

***1b. Lateral spines of abdominal segments 8 and 9 incurved, especially 8. [alleghaniensis]

The lateral spines of abdominal segments 8 and 9 (S8-9) are incurved, especially segment 8 (S8), indicating this species is alleghaniensis.

No. 6 | Macromia alleghaniensis | exuvia (ventral)

This individual is probably a male, as indicated by what appear to be vestigial hamules located on the ventral side of abdominal segments two and three (S2-3).

Summary

A prominent horn on the face is a key field marker for the Family Macromiidae (Cruisers), a small dorsal hook on abdominal segment 10 is one characteristic of the Genus Macromia, and the lateral spines of abdominal segments 8 and 9 (S8-9) are incurved, indicating the species is alleghaniensis. Therefore this specimen is an Allegheny River Cruiser dragonfly (Macromia alleghaniensis).

Bonus Gallery

No. 7 | Macromia alleghaniensis | exuvia (face-head)

No. 8 | Macromia alleghaniensis | exuvia (dorsal-lateral)

No. 9 | Macromia alleghaniensis | exuvia (dorsal)

Related Resources

Tech Tips

The following equipment was used to shoot Photo/Image No. 3-9: 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/Image No. 1 and 2Canon MP-E 65mm Macro lens (manual focus only, set for ~3x magnification) plus the multiple-flash setup.

Image No. 2-8 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017: Image No. 2 (eight photos); Image No. 3 (six photos); Image No. 4 (four photos); Image No. 5 (five photos); Image No. 6 (five photos); Image No. 7 (seven photos); Image No. 8 (seven photos).

Copyright © 2018 Walter Sanford. All rights reserved.

Macromiidae larvae/exuviae are horny

October 4, 2018

A prominent horn on the face is a key field marker for all larvae/exuviae in the Family Macromiidae (Cruisers).

The first image shows the top of the head of an exuvia from an Allegheny River Cruiser dragonfly (Macromia alleghaniensis), collected by Mike Boatwright on 07 June 2018 at Otter Lake in Amherst County, Virginia USA.

07 June 2018 | Amherst County, VA | exuvia (head-horn)

The next photo shows the top of the head of an Allegheny River Cruiser larva reared by fellow Virginian Bob Perkins, providing an excellent view of both the horn and antennae (2).

Image used with permission from Bob Perkins.

Tech Tips

The following equipment was used to shoot the composite image of the exuvia: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (set for 3x); 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 create the focus-stacked composite image from eight photos.

Bob Perkins’ photo of the larva, taken on 03 October 2018, was shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Copyright © 2018 Walter Sanford. All rights reserved.

Latest focus stacking workflow

October 2, 2018

I shot a small set of photos for a focus stack showing the ventral view of an unknown species of odonate exuvia. There are five “slices,” focused from head-to-tail along the body only (no shots focused on legs/feet).

The following gallery shows the five focus points along the body of the specimen, highlighted by a red square.

Although this photo set has fewer “slices” than I have been using to create focus stacks recently (~15-20 photos, on average), the resulting composite image (shown below) is perfectly in focus along the entire body and is serviceable for the purpose of identifying the genus and species of this specimen.

07 June 2018 | Amherst County, VA | exuvia (ventral)

The preceding composite image shows an exuvia from an unknown species of dragonfly (possibly River Cruiser sp.), collected by Mike Boatwright on 07 June 2018 at Otter Lake in Amherst County, Virginia USA. This individual probably is a male, as indicated by vestigial hamules located on the underside of abdominal segments two and three (S2-3).

Shooting the Photo Set

  • Set the camera for Manual Mode.
  • Set the lens for manual focus and turn off image stabilization (when the camera/lens is mounted on a tripod).
  • Compose the image so the frame is a little bigger than the scene you really want. This will give you some wiggle room during post-processing.
  • Set external flash(es) for Manual Mode. (~1/16 power is a good starting point.)
  • Select single focus point; move focus point around image.
  • Live View plus 5x and 10x magnification.
  • Drive mode: 10s timer.
  • DON’T MOVE THE CAMERA. Shoot as many images as necessary.

Advance Preparation – Edit Photos Using 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 Adobe Lightroom.

  • Edit one image: make all adjustments except spot and patch, vignette, and BFX.
  • Right-click on edited photo; select “Lift Adjustments.”
  • <Replace> <Stamp Selected Images>
  • Add metadata: Lift and Stamp selected images.
  • Select images (to be focus stacked); export as TIFFs (16-bit), 300 dpi; save in folder entitled either “TIFF” or “TIFF versions.” File / Export… / Version… [Export Preset: TIFF – Original Size (16-bit)]

Focus Stacking Using Adobe Photoshop

Launch Photoshop.

  • File / Scripts / Load Files into Stack… [Alternate option: Add Open Files <OK>] Do not check the box for “Create Smart Object after Loading Layers.” By default, Ps creates a new document called “Untitled1.”
  • 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. Layer / Duplicate Layers… / Document: New / Name: Backup-copy
  • Select Untitled1: Layer / Merge Layers. (Ps merges all layers into one TIFF, named after first file in sequence.)
  • Straighten and Crop as necessary.
  • Duplicate the layer; append name with “Spot Healing.” [Alternate option: drag layer to copy icon]
  • Remove dust spots from the image: Spot Healing Brush: 27-54 pixels, Content-Aware.
  • Duplicate the layer; append name with “HPF.” [Alternate option: drag Spot Healing layer to copy icon]
  • Select the top layer: Filter / Other / High Pass…; adjust until you can just see outline of image <OK>; change Normal to Overlay. [Don’t oversharpen! ~2.6 used for the composite image featured in this blog post.]
  • Untitled1: Save As… TIFF.
  • Backup-copy (of masked layers): Save As… either PSD or Large Document Format (for documents larger than 2 GB).
  • Import composite TIFF file [Untitled1.tif] into Aperture [or Lightroom]: add additional keywords, as appropriate [e.g., annotated, composite image, focus stack, Photoshop]; Export using BorderBFX.

Tech Tips

The following equipment was used to shoot the composite image (shown above): 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. A Sunpak LED-160 Video Light (with a white translucent plastic filter) was used to add soft light to the underside of the white “stage” used for posing the specimen.

Adobe Photoshop CC 2017 was used to create the focus-stacked composite image from five photos.

Copyright © 2018 Walter Sanford. All rights reserved.

Helocordulia uhleri exuvia

September 14, 2018

An odonate exuvia from the Family Corduliidae (Emeralds) was collected on 06 April 2018 by Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group.

The Backstory

I found a recently-emerged teneral sundragon still clinging to its exuvia along Beck Creek in Amherst County, Virginia USA. Source Credit: Michael Boatwright.

Image used with permission from Michael Boatwright.

After snapping a photo, I gently moved the teneral adult to a nearby blade of grass, snapped another shot, and then collected the exuvia. Although I have seen both Selys’ Sundragon (Helocordulia selysii) and Uhler’s Sundragon (Helocordulia uhleri) in that area, I assumed this one was Selys’ since it’s the more common species there. Source Credit: Michael Boatwright.

Image used with permission from Michael Boatwright.

This is a small genus [Helocordulia] of only two known species found in only the eastern United States and Canada. Source Credit: Needham, J.G., M.J. Westfall, and M.L. May. March 2014. Dragonflies of North America, 3rd Edition: p. 376. Scientific Publishers, Gainesville, Florida.

A two-step process was used to verify 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 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. [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, and no horn on its face-head. Although the specimen is too dirty to see the anal pyramid clearly, field observation of the teneral adult confirms the dragonfly is a member of Genus Heliocordulia (Sundragons) in the Family Corduliidae (Emeralds).

Image No. 1 shows a face-head view of the exuvia, magnified approximately three times life size (~3x). Notice the labium that covers the face is missing one of two palpal lobes; the missing lobe is shown in Image No. 4.

No. 1 | Helocordulia uhleri | exuvia (face-head)

Step 2. Genus and species

The dichotomous key for “Helocordulia larvae” that appears on p. 377 in Dragonflies of North America (Needham, et al.) was used 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 this specimen.

***1. Dorsal hooks on abdominal segments 7-9; palpal setae 7; lateral spines of segment 8 about 1/2 as long as on segment 9 [uhleri]
1’. Dorsal hooks on abdominal segments 6-9; palpal setae usually 6; lateral spines of segment 8 about as long as on segment 9 [selysii]

Image No. 2 shows a dorsal view of the specimen. Notice the mid-dorsal hooks on abdominal segments seven through nine (S7-9), labeled using white text.

No. 2 | Helocordulia uhleri | exuvia (dorsal)

Image No. 3 clearly shows the dorsal hooks on abdominal segments seven through nine (S7-9). This distinctive character confirms the identity of the species as H. uhleri.

No. 3 | Helocordulia uhleri | exuvia (lateral)

Image No. 4 shows a palpal lobe from the specimen, viewed from the inside, magnified approximately three times life size (~3x). There is one palpal seta and at least seven sites where setae might have been located before the palpal lobe broke off the prementum. Although this character is inconclusive for confirming the species (given the condition of the palpal lobe), it’s not exclusive.

No. 4 | Helocordulia uhleri | palpal lobe (inside)

Image No. 5 shows a ventral view of the specimen. Notice the lateral spine on abdominal segment eight (S8) is about half as long as the lateral spine on segment nine (S9).

When measuring spines, I measure them ventral from the inside corner to the tip. There is a suture on the ventral side, near the base, that makes a nice repeatable starting point for measuring. Source Credit: Ken Tennessen, personal communication.

No. 5 | Helocordulia uhleri | exuvia (ventral)

Takeaways

Perhaps the biggest takeaway from working to identify this exuvia is the fact that it enabled the correct identification of the teneral adult dragonfly that Mike observed and photographed. In fact, Mike is the one who first recognized the species is H. uhleri, based upon the number of mid-dorsal hooks on the exuvia.

Tech Tips

Mike Boatwright’s photographs, taken in-situ, were shot using a Canon EOS 7D digital camera and Canon 300mm prime lens paired with a Canon 1.4x Extender EF.

The following equipment was used to shoot Image No. 2, 3, and 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 and 4Canon MP-E 65mm Macro lens (manual focus only, set for ~3x 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 (seven photos); Image No. 2 (30 photos); Image No. 3 (16 photos); Image No. 4 (10 photos); Image No. 5 (24 photos).

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.


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