Posts Tagged ‘male’

Life and death at Occoquan Bay revisited

September 16, 2018

I revisited the set of photos that I shot of an Osprey (Pandion haliaetus) with a fish in its talons, perched on a dead tree limb overhanging Fox Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia.

The Osprey was looking at me directly in the following photo. I wonder what the bird was thinking. With a piercing glare like that, I’m guessing he wasn’t thinking “Would you like to join me for lunch?”

23 AUG 2018 | Occoquan Bay NWR | Osprey (male, plus prey)

In stark contrast with the Osprey’s piercing glare, notice the fish’s vacant stare.

Copyright © 2018 Walter Sanford. All rights reserved.

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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.

Life and death at Occoquan Bay

August 27, 2018

An Osprey (Pandion haliaetus) was spotted perched on a dead tree limb overhanging Fox Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. This individual, possibly a male, is shown with a fish in its talons.

23 AUG 2018 | Occoquan Bay NWR | Osprey (male, plus prey)

The fish appears to be an unknown species of goldfish. Did you notice the drop of blood in the preceding photo?

Copyright © 2018 Walter Sanford. All rights reserved.

Blue-fronted Dancer damselflies (male, females)

August 7, 2018

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

Male

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

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

Female

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

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

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

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

Copyright © 2018 Walter Sanford. All rights reserved.

You look Familiar

August 3, 2018

A Familiar Bluet damselfly (Enallagma civile) was spotted during a photowalk along one of many trails at Occoquan Regional Park, Fairfax County, Virginia USA.

08 JUN 2018 | Occoquan Regional Park | Familiar Bluet (male)

This individual is a male, as indicated by the pattern of coloration on his abdomen. Female E. civile is polymorphic, including two morphs: tan; and blue. Female blue morphs have a different pattern of black and blue markings on their abdomen than males of the same species.

Editor’s Note

Sincere thanks to my good friend Mike Boatwright, administrator of the Virginia Odonata Facebook group, for verifying my tentative identification.

Related Resource: Familiar Bluet damselfly (female).

Copyright © 2018 Walter Sanford. All rights reserved.

“Lost” photos, redux

August 1, 2018

Another Gray Petaltail dragonfly (Tachopteryx thoreyi) was spotted at the same location in Prince William County, Virginia USA as the one featured in my last blog post.

08 JUN 2018 | Prince William County, VA | Gray Petaltail (male)

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

08 JUN 2018 | Prince William County, VA | Gray Petaltail (male)

The mid-size fallen tree on which the male is perched proved to be a good spot to find Gray Petaltail during every visit to the site.

Related Resource: Gray Petaltail dragonfly (male).

Copyright © 2018 Walter Sanford. All rights reserved.

Gray Petaltail dragonfly (male)

July 30, 2018

Two photo sets of Gray Petaltail dragonfly (Tachopteryx thoreyi), taken on 08 June 2018 at an undisclosed location in Prince William County, Virginia USA, were lost in the excitement of my rediscovery of Sable Clubtail dragonfly (Stenogomphurus rogersi) later the same day in Fairfax County, VA. This gallery is one of two posts featuring some of the “lost” photos.

08 JUN 2018 | Prince William County, VA | Gray Petaltail (male)

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

08 JUN 2018 | Prince William County, VA | Gray Petaltail (male)

The Gray Petaltail ambushed several smaller insects that flew near his perch; he always returned to the same tree after each brief excursion.

08 JUN 2018 | Prince William County, VA | Gray Petaltail (male)

Related Resource: “Lost” photos, redux.

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 forested 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.

Sable Clubtail (terminal appendages)

July 18, 2018

Male and female Sable Clubtail dragonflies (Stenogomphurus rogersi) were spotted recently in Fairfax County, Virginia USA.

Male

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”). The epiproct for Sable Clubtail is essentially a wide plate with two prongs.

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

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

The hind wings of male clubtail dragonflies are “indented” near the body, as shown in the preceding photograph. In contrast, the hind wings of female clubtails are rounded (shown below).

Female

Female dragonflies have a pair of cerci (superior appendages) that have little or no function. The abdomen of female Sable Clubtails is noticeably thicker than males of the same species.

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

Copyright © 2018 Walter Sanford. All rights reserved.


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