Posts Tagged ‘Family Corduliidae (Emeralds)’

Baskettail dragonflies

May 10, 2019

Several species of baskettail dragonflies (Epitheca sp.) are among the first odonates to emerge in spring.

22 APR 2019 | PRR | baskettail dragonfly (Epitheca sp.)

Two baskettail dragonflies, possibly either Common Baskettail (E. cynosura) or Slender Baskettail (E. costalis), were spotted at the North Tract of Patuxent Research Refuge, Anne Arundel County, Maryland USA.

Look closely at the full-size version of the following photo. Notice the leading edge of the left fore-wing is slightly malformed.

22 APR 2019 | PRR | baskettail dragonfly (Epitheca sp.)

[Baskettails] have proven to be very difficult to identify, particularly from photographs. Most species are quite variable and there is evidence that they may hybridize and or integrade, making identifications even tougher. Source Credit: Identification of Male Epitheca (Tetragoneuria) in Texas, by John C. Abbott.

I’m unable to identify these dragonflies to the species level. In fact, I’m not sure they’re the same species! I defer to odonate hunters with more expertise than me for help with identification of both species and gender.

Post Addendum

According to Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, both individuals are male Common Baskettail. Male Common- and Slender Baskettail have curved cerci; females of both species have straight cerci. That’s good baskettail knowledge, Mike Boatwright!

Copyright © 2019 Walter Sanford. All rights reserved.

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Beware of dismissive thinking!

April 26, 2019

An unknown species of teneral baskettail dragonfly (Epitheca sp.), possibly either Common Baskettail (E. cynosura) or Robust Baskettail (E. spinosa), was spotted near a mid-sized pond at the North Tract of Patuxent Research Refuge, Laurel, Maryland USA.

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

That’s a very wide abdomen, hairy thorax, and cerci as long (if not slightly longer) as S9. I’m fairly confident it’s a Robust Baskettail but I have limited experience with that species. The pattern of dark spots at the wing base is definitive for Robust but I can’t see them well in your picture. Mike Moore’s opinion would he good. Source Credit: Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group.

I consulted Dr. Michael Moore.

It certainly suggests Robust based on the dimensions of the abdomen and the “hairiness” of the thorax but I would really need to see the pattern of black at the base of the hind wings to be sure. Female Commons can be surprisingly fat. Source Credit: Dr. Michael Moore, a professor in the Department of Biological Sciences at University of Delaware and odonate expert extraordinaire. Dr. Moore’s new Web site is a treasure trove of helpful resources.

The reason neither Mike nor Michael can see the definitive field mark on the base of the baskettail dragonfly’s hind wings is because this individual is a late-stage emergent teneral and its wings haven’t opened.

Regardless of the species of dragonfly, emergence is an essentially identical process. See “Related Resources” (below) for a time-series of photographs showing part of the process of emergence for a female Common Baskettail.

The danger of dismissive thinking.

This sighting was another reminder of one of many “Walterisms”: “Don’t be dismissive!” Huh?

During a recent trip to the Patuxent Research Refuge in search of Harlequin Darner (G. furcillata), my good friend Mike Powell and I saw many basktettails, mostly Common Baskettail. Common. That’s the key word. When I noticed several baskettails, I thought, “Oh, Common Baskettails. Nothing to see here, folks. Move along. Must find Harlequin!”

As it turns out, my laser-like focus on finding my first Harlequin Darner might have caused me to miss an opportunity to see a Robust Baskettail — another new species for my life list of odonates. Once again I’m reminded that dismissive thinking can be wrong-headed.

Related Resources

Copyright © 2019 Walter Sanford. All rights reserved.

Uhler’s Sundragon (female)

April 19, 2019

A Uhler’s Sundragon (Helocordulia uhleri) was spotted during a photowalk along a mid-size stream at an undisclosed location in Northern Virginia USA.

This individual is a female, as indicated by her rounded hind wings and terminal appendages. All female dragonflies have a pair of cerci (superior appendages) that have little or no function. Both cerci are visible clearly in the full-size version of the following photo.

16 APR 2019 | Northern Virginia | Uhler’s Sundragon (female)

Notice the right hind wing is slightly malformed. It appears the wing failed to inflate completely during emergence. The malformation didn’t impair her ability to fly. Pollen (probably tree pollen) is especially noticeable on the darker parts of the body.

Just the facts, ma’am.

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 H. uhleri is 29 March to 27 June. The species is classified as common. Its habitat is “streams.”

Bear in mind, Dr. Roble’s records are for the entire state, therefore the adult flight period for H. uhleri seems to be longer than it is in reality. The adult flight period for a single site is probably no more than a month, and more likely around two-to-three weeks. For example, according to records for Northern Virginia maintained by Kevin Munroe, former manager of Huntley Meadows Park, the adult flight period for Uhler’s is 11 April to 05 May.

It’s also worth noting that the window of opportunity to see Uhler’s Sundragon closes rapidly after trees are in full leaf.

Is Uhler’s Sundragon common? I guess the answer to that question depends upon where you live. In Northern Virginia, Kevin Munroe classified H. uhleri as “rare.” In fact, I’m aware of only one location in Northern Virginia where Uhler’s Sundragon can be found with reasonable certainty.

Copyright © 2019 Walter Sanford. All rights reserved.

Uhler’s Sundragon (male)

April 17, 2019

A Uhler’s Sundragon (Helocordulia uhleri) was spotted during a photowalk along a mid-size stream at an undisclosed location in Northern Virginia USA. Uhler’s Sundragon is a new species for my life list of odonates.

16 APR 2019 | Northern Virginia | Uhler’s Sundragon (male)

This individual is a male, as indicated by its “indented” hind wings and terminal appendages.

Off-season Homework Pays Dividends

Planning for the next season is a good way to stay connected with odonates during the winter months. One off-season activity that can pay big dividends in the future is to research sites for finding new life-list species of dragonflies and damselflies, especially rare and uncommon species.

Uhler’s is No. 1 on my list of target species for 2019. During the winter of 2018-2019, I researched potential sites for finding Uhler’s Sundragon. I’m pleased to report “Mission accomplished!”

Credits

I’ve been dogged by, er, let’s just say “transportation issues” for months. Sincere thanks to my buddy Mike Powell for scouting one of the sites I researched and guiding me to a couple spots where he found Uhler’s. Good work, Mike — couldn’t have done it without you!

Also thanks to Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, for providing lots of practical tips for finding Uhler’s Sundragon in the field.

Related Resources

Copyright © 2019 Walter Sanford. All rights reserved.

“Generic Baskettail” (definitely not a Cruiser)

February 18, 2019

larva/nymph in the Family Corduliidae (Emeralds) was collected by Bob Perkins on 02 December 2017 from a pond in Orange Park, Florida (USA). The larva died before it metamorphosed into an adult.

As you can see by looking at a close-up image of the face-head at 3x magnification, there is no horn on the face of the specimen. Therefore this individual is not a member of Family Macromiidae (Cruisers), as I speculated in my last blog post.

“Generic Baskettail” larva (preserved specimen) | face-head

Knowing the limits of our expertise

Although I still need to key out the specimen carefully, at this point I’m certain Bob is correct — the larva is a member of the Family Corduliidae (Emeralds). The question that remains unanswered is “Which genus/species?” We may never know the answer, as Bob and I have reached the limit of our experience and expertise.

I did a quick scan of Paulson’s [book], looking at the Emerald Family. Here, according to the range maps, are the possibilities for Orange Park [FL]. I believe you can see why I stopped at “generic basketttail.” Source Credit: Bob Perkins.

What do you think the identity is? Most of the items in the preceding species list feature links to photos of odonate larvae/exuviae. See the links to BugGuide from the scientific names in the list.

Related Resource: Test shots: “Generic Baskettail?”

Tech Tips

Four (4) photos were used to create the preceding focus-stacked composite image. A single focus point was positioned over the face, between the antennae. At a magnification ratio of 3:1, it’s difficult to manually focus on a single point — the slightest movement around the macro rig changes focus unintentionally. A simple work-around for this problem is to take several shots of the same focus point and create a composite image of the photos.

The following equipment was used to shoot the preceding composite image: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (set for f/16 at 3x); a Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and a single external flash set for “Slave” mode — a Godox TT685C Thinklite TTL Flash fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier. A Sunpak LED-160 Video Light was used to add fill light to the top of the subject.

Auto power-off was disabled for the camera and external flash units.

Adobe Photoshop CC 2017 was used to create the focus stack, as well as spot-heal and sharpen the final output.

Copyright © 2019 Walter Sanford. All rights reserved.

Test shots: “Generic Baskettail?”

February 15, 2019

larva/nymph in the Family Corduliidae (Emeralds) was collected by Bob Perkins on 02 December 2017 from a pond in Orange Park, Florida (USA). The larva died before it metamorphosed into an adult.

Test shots of this beautifully preserved specimen were taken using a small-ish aperture of f/11 for greater depth of field. The following photos are “one-offs,” that is, not composite images.

Dorsal

A single focus point — located on the thorax (specifcally, the “shoulder pad” along the right side of the body) — was used to shoot this photo. The specimen has enough “relief” that focus on the wing pads and dorsal hooks is slightly soft. This view of the larva is a good candidate for focus-stacking.

The terminal appendages (cerci, epiproct, paraprocts) are shown clearly in the following photo.

“Generic Baskettail” larva (preserved specimen) | Orange Park, FL USA

Bob’s best guess of the identity of the specimen is Epitheca sp., either Common Baskettail (Epitheca cynosura) or Prince Baskettail (Epitheca princeps).

Whenever I see an odonate larvae/exuviae with long legs, my first thought is Family Macromiidae (Cruisers). Then I check for a horn on top of the head, a key field marker for Cruisers. Look closely at the dorsal view of the larva and I think you’ll agree with me there appears to be a horn on the head. I would like to take close-up photos of the head and key out the specimen in order to determine its identity. In the meantime, my best guess is Stream Cruiser (Didmops transversa) as indicated by the lateral spines on abdominal segment nine (S9) and the absence of a dorsal hook on S10.

Ventral

The ventral side of the specimen has almost no “relief,” so a “one-off” focused on the thorax looks fairly good from head-to-tail.

“Generic Baskettail” larva (preserved specimen) | Orange Park, FL USA

Related Resource: “Generic Baskettail” (definitely not a Cruiser)

Tech Tips

The following equipment (shown below) was used to shoot the preceding photos: Fujifilm X-T1 digital camera; Fujifilm MCEX-16 extension tube; Fujinon XF80mm macro lensGodox XProF TTL Wireless Flash Trigger for Fujifilm camerasGodox TT685F Thinklite TTL Flash for Fujifilm CamerasGodox TT685C Thinklite TTL Flash for Canon Cameras fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier; and a Canon 580EX II Speedlite mounted on a Godox X1R-C TTL Wireless Flash Trigger Receiver for Canon. A new Godox TT685O Thinklite TTL Flash for Olympus/Panasonic Cameras was added to an array of radio-controlled external flash units used to light the specimen. All flashes were set for Manual Mode at 1/128 power.

Adobe Photoshop CC 2017 was used to spot-heal and sharpen the final output.

Copyright © 2019 Walter Sanford. All rights reserved.

Pot o’ Emeralds

December 17, 2018

The following photo shows a plastic container of 20 Downy Emerald dragonfly (Cordulia aenea) exuviae, collected by a good friend during April 2018 in Vienna, Austria. Not a pot o’ gold at the end of a rainbow, but valuable treasure nonetheless!

Thanks to field marks shared by Benoit Guillon, I was able to quickly determine that all of the exuviae are the same species as the specimen featured in a recent blog post.

Benoit’s excellent Web pages are written in French. I used the Google Chrome Web browser to translate French to English.

The exuvia of the Tanned Cordulia is easy to recognize, provided you have good eyes or … a magnifying glass. It is indeed only to present a line, or double black line, on the thorax, clearly visible on the enlargement of the photo on the top left [see Benoit’s Web page]. She also has very large legs and we easily notice the teeth of the palps of her [face] mask in the photo above [see Benoit’s Web page]. As for his eyes, even if they are spectacular [sic?], some other odonate varieties are also strange. Source Credit: Benoit Guillon.

The key field marks — shown in the following focus-stacked composite image — include one- or two dark lines along the thorax, and a dark line between its small, pointy eyes.

Related Resource: Cordulia aenea: exuviae (1/2), by Benoit Guillon.

Tech Tips

I used my Panasonic Lumix DMC-FZ150 superzoom camera and a handheld Canon 580EX Speedlite fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier to shoot the first photo featured in this blog post.

The following equipment was used to shoot all of the photographs for the focus-stacked 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); 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 focus-stacked composite image, as well as spot-heal and sharpen the final output.

Copyright © 2018 Walter Sanford. All rights reserved.

Test shots: Unknown odonate exuvia

December 12, 2018

An odonate exuvia from an unknown species of dragonfly (Anisoptera) was collected by a good friend during April 2018 in Vienna, Austria.

Based upon the crenulations along the margins of the labium, I think the specimen is a member of either the Family Corduliidae (Emeralds) or Family Libellulidae (Skimmers). I need to clean the anal pyramid for a clearer look at the terminal appendages in order to identify the family.

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.

Anisoptera (unknown species) | exuvia (face/head-dorsal)

Composite images

The next two “photos” are three-layer focus-stacked composite images: For each 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 most of the legs.

The specimen has dorsal hooks on some abdominal segments (exact number unknown without closer examination), and lateral spines on abdominal segments eight and nine (S8-9).

Anisoptera (unknown species) | exuvia (dorsal)

I think this individual might be a female, as indicated by what appears to be a rudimentary ovipositor that is visible on the ventral side of abdominal segment nine (S9).

Anisoptera (unknown species) | exuvia (ventral)

Post Update

Sincere thanks to Benoit Guillon and Christophe Brochard, members of the “Dragonflies and Damselflies – Worldwide Odonata” Facebook group, for kindly identifying this specimen as an exuvia from a Downy Emerald dragonfly (Cordulia aenea). Downy Emerald is a member of the Family Corduliidae (Emeralds).

The following photo shows a plastic container of 20 Downy Emerald dragonfly (Cordulia aenea) exuviae, collected by a good friend during April 2018 in Vienna, Austria. Thanks to field marks shared by Benoit Guillon, I was able to quickly determine that all of the exuviae are the same species as the specimen featured in this blog post.

Related Resource: Cordulia aenea: exuviae (1/2), by Benoit Guillon.

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 create the two focus-stacked composite images, as well as spot-heal and sharpen the final output.

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.

More Mocha males

July 20, 2018

Nearly two weeks after my last visit to Huntley Meadows Park in search of Mocha Emerald dragonfly (Somatochlora linearis), I revisited the small forest stream in search of Mocha exuviae.

No luck finding exuviae, but hey, I decided to make lemonade from lemons and photograph a couple of Mocha males that hung up near each other, especially since there were noticeably fewer S. linearis in contrast with my last trip to the site.

Male 1

Both individuals are male, as indicated by their “indented” hind wings and terminal appendages.

Male 2

Copyright © 2018 Walter Sanford. All rights reserved.


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