Posts Tagged ‘cerci’

Phanogomphus

April 20, 2017

Two teneral dragonflies were observed near Mulligan Pond during a photowalk at Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. I was able to photograph the first one I spotted; the second flew away as soon as I approached it.

This dragonfly is either Ashy Clubtail (Phanogomphus lividus) or Lancet Clubtail (Phanogomphus exilis). Based upon the short, faded yellow markings on the dorsal side of abdominal segments eight and nine (S8-9), this individual is probably an Ashy Clubtail dragonfly. Less reliably, the 18 April date of the spotting also suggests Ashy Clubtail (for Northern Virginia).

18 APR 2017 | JMAWR | Ashy Clubtail or Lancet Clubtail (female)

Both Ashy- and Lancet Clubtail dragonflies were formerly classified as members of the genus Gomphus. Both species were reclassified recently as Phanogomphus. In the world of taxonomic classification, there are “lumpers” and “splitters.” Score one for the splitters!

Notice the first photo shows the wings folded above the abdomen. I spotted the teneral dragonfly when it flew toward me from the pond shoreline. The dragonfly rested in this location for a few minutes before it flew to a new spot (shown below) where it perched briefly with its wings unfolded. The last time I saw the dragonfly, it was flying toward the forest alongside the pond.

The other teneral dragonfly that I saw — “the one that got away” — was perched on the lawn near the walking path around the lake; it flew toward the forest when I moved closer to take some photographs.

18 APR 2017 | JMAWR | Ashy Clubtail or Lancet Clubtail (female)

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

This specimen is a female, as indicated by her rounded hind wings and terminal appendages.

All female dragonflies have two cerci (superior appendages); in contrast all male dragonflies have two cerci and one epiproct (inferior appendage), collectively called “claspers.” Contrast the appearance of the terminal appendages of this female Ashy Clubtail with a male of the same species.

The last photo in the set is a wider view that shows how well-camouflaged the dragonfly was perched on the lawn around the pond.

18 APR 2017 | JMAWR | Ashy Clubtail or Lancet Clubtail (female)

The Backstory

I was surprised to discover a Lancet Clubtail dragonfly near Mulligan Pond during late-June 2016. Knowing that Ashy Clubtails can be found in the same habitats preferred by Lancet Clubtails, I decided to look for Ashy Clubtails at Jackson Miles Abbott Wetland Refuge beginning in mid-April 2017. Apparently Mulligan Pond is a good place for both species, because I spotted two Ashy Clubtails the first time I went looking for them. Ah, if only odonate hunting were always so easy!

Copyright © 2017 Walter Sanford. All rights reserved.

Late-stage emergent baskettail dragonfly

April 18, 2017

Common Baskettail dragonfly (Epitheca cynosura) was spotted at Painted Turtle Pond during a photowalk around Occoquan Bay National Wildlife Refuge (OBNWR), Prince William County, Virginia USA. This individual is a late-stage emergent teneral female.

I photographed the process of emergence from the first sighting to the time when the teneral dragonfly flew away: I shot 23 photos in approximately 16 minutes; time is compressed by showcasing six (6) select photos taken at major milestones during the event.

The following photo is the first image from a time-series documenting the emergence of the teneral female. Elapsed time is expressed in hh:mm:ss format, e.g., 00:00:00 is the time when I spotted the emergent teneral female, and 00:16:08 is the total elapsed time.

13 APR 2016 | 11:38:41 am EDT | Elapsed time: 00:00:00

Notice the drop of fluid at the tip of the abdomen. Emerging dragonflies pump fluid into their wings, causing the wings to expand. Next, the same fluid is withdrawn from the wings and used to expand the abdomen. Excess fluid is expelled afterward.

13 APR 2016 | 11:40:48 am EDT | Elapsed time: 00:02:07

The next photo shows the first time the wings opened.

13 APR 2016 | 11:48:55 am EDT | Elapsed time: 00:10:14

Then the wings closed again and remained closed for a while.

13 APR 2016 | 11:51:02 am EDT | Elapsed time: 00:12:21

The wings reopened a few minutes later. Notice that several wings are malformed slightly.

13 APR 2016 | 11:54:14 am EDT | Elapsed time: 00:15:33

Finally, the wings open up, and very soon the teneral adult flies away. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 468). Princeton University Press. Kindle Edition.

The teneral female dragonfly flew away immediately after the last photo in the time-series.

13 APR 2016 | 11:54:46 am EDT | Elapsed time: 00:16:08

This individual is a female, as indicated by her cerci (superior appendages) and thick abdomen. Common Baskettail females have shorter cerci and a thicker abdomen than males of the same species.

Exuviae (in situ)

Several dragonfly exuviae were spotted at Painted Turtle Pond; it’s possible they are cast skins from Common Baskettail. More later after the exuviae are identified using a dichotomous key for dragonfly larvae.

13 APR 2017 | OBNWR | Common Baskettail (exuvia)

These exuviae are not the one from which the teneral female featured in this post emerged.

13 APR 2017 | OBNWR | Common Baskettail (exuvia)

Copyright © 2017 Walter Sanford. All rights reserved.

Common Baskettail dragonfly (male)

April 16, 2017

A Common Baskettail dragonfly (Epitheca cynosura) was spotted near Painted Turtle Pond during a photowalk at Occoquan Bay National Wildlife Refuge (OBNWR). Common Baskettail is a member of Family Corduliidae (Emeralds); this species is seen during early spring in mid-Atlantic United States like Virginia.

I thought this might be a Slender Baskettail dragonfly (Epitheca costalis) due to narrowing of its abdomen. Turns out that was wishful thinking.

13 APR 2017 | OBNWR | Common Baskettail (male)

This individual is a male, as indicated by his terminal appendages. The curved shape of the cerci (superior appendages) is a key field marker for Common Baskettail; in contrast, the cerci for Slender Baskettail tend to be more parallel. Thanks to Mike Boatwright and Paul Guris, members of the Northeast Odonata Facebook group, for reminding me of this pearl of wisdom!

I think baskettail cerci look “rubberized,” like the handles of metal tools made for working with electricity. Whenever I see this distinctive field marker, shown clearly in the following photos, I know the dragonfly is probably a species of baskettail.

13 APR 2017 | OBNWR | Common Baskettail (male)

The last photo shows a dorso-lateral view of the male dragonfly. Notice the epiproct (inferior appendage) is visible clearly in this photo.

13 APR 2017 | OBNWR | Common Baskettail (male)

Also notice the light-colored spots on the hairs covering the body of the dragonfly. The following article by John Abbott suggests the spots may be some type of pollen.

Related Resource: Identification of Male Epitheca (Tetragoneuria) in Texas, by John C. Abbott.

Copyright © 2017 Walter Sanford. All rights reserved.

Painted Skimmer dragonfly (teneral female)

March 19, 2017

Painted Skimmer dragonfly (Libellula semifasciata) was spotted at a vernal pool in Huntley Meadows Park (HMP). This individual is a teneral female, as indicated by her terminal appendages and the tenuous appearance of her wings.

No. 1 | 31 MAY 2016 | HMP | Painted Skimmer (teneral female)

Shine on you crazy diamond!

No. 2 | 31 MAY 2016 | HMP | Painted Skimmer (teneral female)

Although Photo No. 1 and 3 look similar, I posted both pictures. Photo No. 1 shows the tenuous appearance of the wings best of all four photos, but I prefer the composition of Photo No. 3. Which one of the two photos do you prefer?

No. 3 | 31 MAY 2016 | HMP | Painted Skimmer (teneral female)

Teneral dragonflies are skittish and prefer to perch in “hidey-holes” that offer protection from predators like paparazzi wildlife photographers. The dragonfly is perching on “soft rush” (Juncus effusus), the common name for the shoreline/emergent plant with light green round stems and brownish flowers that appears in the entire photo set. Soft rush is common in wetland areas.

No. 4 | 31 MAY 2016 | HMP | Painted Skimmer (teneral female)

Painted Skimmer dragonflies do not display sexual dimorphism, that is, adult females and males look similar except for their terminal appendages. Female dragonflies have a pair of cerci (superior appendages) that have little or no function; male dragonflies have three terminal appendages, collectively called “claspers.” The cerci are easy to see in the full-size version of the preceding photo.

Copyright © 2017 Walter Sanford. All rights reserved.

Epitheca princeps exuvia

March 5, 2017

The following Prince Baskettail dragonfly (Epitheca princeps) exuvia, on temporary loan from a friend, had been identified before I borrowed the specimen. 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 that covers the face, characteristic of four families: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).
  • There is no horn on top of 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 [See Photo No. 4.]: 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, 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).

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

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

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

Step 2. Genus and species

Characters from two dichotomous keys were used to identify the genus and species for the exuvia. Although palpal/mental setae were not examined, all other characters match Epitheca princeps.

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

Dichotomous Key 1

Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz.

Key to the Families of Anisoptera, page 5.

Key to the Genera of the Family Corduliidae, page 28.

Dichotomous Key 2

Corduliidae Selys – EmeraldsOdonata Nymphs of Michigan, by Ethan Bright and Mark F. O’Brien, UMMZ-Insect Division.

Epitheca Burmeister, 1839 (Corduliidae) – Baskettails

  • 1a. Distal half of dorsal surface of prementum heavily setose; palpal setae usually 4, rarely 5(Fig. 2) – Subgenus Epicordulia, E. princeps

More annotated images

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

No. 2 | Prince Baskettail (Epitheca princeps) | exuvia (dorsal)

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

Mid-dorsal hooks present, well-developed on some abdominal segments.”

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

No. 3 | Prince Baskettail (Epitheca princeps) | exuvia (dorso-lateral)

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

“With lateral spines on Ab8 [S8].” “Lateral spines on Ab9 [S9] at least 2.0x as long as those on Ab8 [S8], at least equal to mid-dorsal length of Ab9 [S9].” The cerci are at least half as long as the paraprocts.

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

No. 4 | Prince Baskettail (Epitheca princeps) | exuvia (anal pyramid)

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

Photo No. 5 shows a wider view of the ventral side of the specimen.

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

No. 5 | Prince Baskettail (Epitheca princeps) | exuvia (ventral)

Photo No. 6 shows a zoomed-in view of the prementum.

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

No. 6 | Prince Baskettail (Epitheca princeps) | exuvia (prementum)

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

Photo No. 7 shows another view of the prementum.

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

No. 7 | Prince Baskettail (Epitheca princeps) | exuvia (prementum)

Tech Tips:

The following equipment was used to shoot all of the preceding photographs: Canon EOS 5D Mark II digital camera, in manual mode; Canon EF100mm f/2.8L Macro lens (set for manual focus) plus a Kenko 20mm macro automatic extension tube and a Raynox DCR-250 close-up filter; Canon 580EX II external flash, off-camera, in manual mode; Canon 580EX external flash, off-camera, in manual mode; and a Yongnuo YN-622C-TX E-TTL II Wireless Flash Controller for Canon plus a two-pack of Yongnuo YN-622C II E-TTL Wireless Flash Transceivers for Canon.

A Canon Extender EF 1.4x II was used for more magnification in Photo No. 4, 6, 7 and 9. Adding the tele-extender results in a 1 f/stop loss of light; additional backlight was added to the scene using a Nissin i40 external flash unit (off-camera, in SF mode).

Adobe Photoshop CC 2017 was used to annotate selected images.

Photo No. 8 and 9 show early work to get a good shot of the face-head, before Photo No. 1 emerged as the clear winner. I prefer Photo No. 1 because it provides the best view of the face-head, has the best composition and exposure, plus I like the way the exuvia seems to be floating in mid-air.

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

No. 8 | Prince Baskettail (Epitheca princeps) | exuvia (face-head)

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

No. 9 | Prince Baskettail (Epitheca princeps) | exuvia (face-head)

Although I have never seen a perching adult Prince Baskettail dragonfly, I was fortunate to shoot the following photo of a male in flight, featured in the blog post Changing of the guard.

A Prince Baskettail dragonfly (Epitheca princeps) spotted at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a male, shown in flight.

No. 10 | 14 JUN 2016 | JMAWR | Prince Baskettail (male, in flight)

Related Resources:

Copyright © 2017 Walter Sanford. All rights reserved.

Gomphurus vastus exuvia

February 17, 2017

10s, maybe 100s of adult Cobra Clubtail dragonflies (Gomphurus vastus) were spotted on 16 May 2016 during a photowalk along the Potomac River at Riverbend Park, Fairfax County, Virginia USA. Cobra Clubtails were the only species of odonate observed in a period of several hours.

A Cobra Clubtail dragonfly (Gomphurus vastus) spotted at Riverbend Park, Fairfax County, Virginia USA. This individual is a male.

No. 1 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (adult male)

A single exuvia (shown below) from an unknown species of dragonfly was collected with permission from park staff. If adult Cobra Clubtail dragonflies were common, then the specimen is probably a Cobra Clubtail exuvia, right? Let’s test our hypothesis.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 2 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (exuvia)

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 that doesn’t cover the face (not mask-like). [See Photo No. 3.]
  • Antennae are club-like (not thin and thread-like, as in Aeshnidae). [See Photo No. 3.]
  • Eyes not exceptionally large compared to the size of the head (not large, as in Aeshnidae). [See Photo No. 3.]
A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 3 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (exuvia, face-head)

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

Step 2. Genus and species

Gomphidae is the second largest family of dragonflies, so it can be challenging to identify some specimens to the genus and species level.

Characters from two dichotomous keys were used to identify the exuvia, in part, due to confusion caused by the fact that the name for the genus to which Cobra Clubtail belongs was changed recently from Gomphus to Gomphurus. As a result, the workflow for identifying this specimen was a little “jumpier” than usual.

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

Dichotomous Key 1

Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz. Cobra Clubtail (Gomphus vastus), p. 15, Key to the species of the genus Gomphurus.

  • 1a – Strongly hooked palpal lobes with few teeth (3-5). Gomphurus group I (2) [See Photo No. 8.]
  • 2a – Length 27-30 mm. (vastus) [See Photo No. 4, below.]
A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 4 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (exuvia, dorsal)

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

Dichotomous Key 2

“Gomphus complex” (= Gomphini) – Clubtails, Odonata Nymphs of Michigan.

  • 1b. Middorsal length of Ab9 [S9] less than half its basal width (fig); length of Ab10 [S10] < 0.50x its width (fig) – 6 [See Photo No. 6.]
  • 6b. Lateral spines of Ab9 close to Ab10, markedly longer than those on Ab8 (fig) [S8]; abdomen appears dorsoventrally flattened (fig) – Gomphurus, 8 [See Photo No. 6.]
  • 8b. Apical margin of median lobe of prementum straight or slightly convex (fig) – 9 [See Photo No. 8.]
  • 9a.(8b). End hook of lateral lobe of labium strongly incurved, extending far past apex of the truncate, 3 to 4 lateral teeth next to it (fig) – Gomphurus vastus
A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 5 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (exuvia, posterior)

The preceding photograph shows a wider view of the posterior end of the abdomen. A closer view of the anal pyramid helps to illustrate several of the morphological characters described in Dichotomous Key 2.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 6 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (exuvia, anal pyramid)

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

The basal width of abdominal segment nine (S9) was measured in a straight line from edge-to-edge across the abdomen. The same distance would be longer if it were measured along the joint between abdominal segments eight and nine (S8 and S9). Either way the basal width is measured, the middorsal length is less than half of the basal width.

Since the middorsal length of abdominal segment 10 (S10) is clearly less than its basal width, the character wasn’t illustrated in the preceding annotated image.

Looking carefully at the anal pyramid, notice the cerci (sing. cercus) are slightly shorter than the epiproct, and the epiproct is almost as long as the paraprocts.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 7 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (exuvia, ventral)

Photo No. 7 shows a wider view of the ventral side of the specimen. Zooming in on the prementum helps to illustrate some of the morphological characters described in Dichotomous Key 2.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 8 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (exuvia, prementum)

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

Tech Tips:

The following equipment was used to shoot all of the preceding photographs: Canon EOS 5D Mark II digital camera, in manual mode; Canon EF100mm f/2.8L Macro lens (set for manual focus) plus a Kenko 20mm macro automatic extension tube; Canon 580EX II external flash, off-camera, in manual mode; Canon 580EX external flash, off-camera, in manual mode; and a Yongnuo YN-622C-TX E-TTL II Wireless Flash Controller for Canon plus a two-pack of Yongnuo YN-622C II E-TTL Wireless Flash Transceivers for Canon.

Raynox DCR-250 close-up filter was used for Photo No. 3, 6, and 8. A Canon Extender EF 1.4x II was used for more magnification in Photo No. 8. Adding the tele-extender results in a 1 f/stop loss of light; additional backlight was added to the scene using a Nissin i40 external flash unit (off-camera, in SF mode).

Adobe Photoshop CC 2017 was used to annotate selected images.

The following photograph of another dragonfly exuvia was taken in-situ along the shoreline of the Potomac River using a Panasonic DMC-FZ150 superzoom bridge camera and Canon 580EX Speedlite, my go-to kit for photowalking. There were many exuviae clinging to the concrete retaining wall shown in the photo. Photo No. 1 was taken using the same camera-flash combo.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) photographed in situ at Riverbend Park, Fairfax County, Virginia USA.

9. | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (exuvia, in situ)

Related Resources:

Editor’s Note: Sincere thanks to Sue Gregoire for her kind mentorship. Sue patiently provides guidance regarding the scientific jargon that can make it either challenging (at best) or impossible to understand many dichotomous keys for the identification of odonate larvae/exuviae. Like every good teacher, Sue doesn’t “give me a fish” — she teaches me how to fish. Thanks again, Sue!

Copyright © 2017 Walter Sanford. All rights reserved.

Eastern Shieldbacks

January 10, 2017

Two Eastern Shieldbacks (Atlanticus sp.) were spotted along the Hike-Bike Trail as I was walking out of Huntley Meadows Park. Eastern Shieldbacks are a type of Katydid (Family Tettigoniidae).

Male

This individual is a male. Notice the pair of cerci (sing. cercus) at the tip of his abdomen. Cerci are anatomical structures that are familiar to experienced odonate hunters like me.

Female

The following individual is a female, as indicated by the long ovipositor that extends from the tip of her abdomen.

An Eastern Shieldback (Atlanticus sp.) spotted along the Hike-Bike Trail at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a female.

24 JUN 2016 | Huntley Meadows Park | Eastern Shieldback (female)

Notice the female has two cerci and an ovipositor.

An Eastern Shieldback (Atlanticus sp.) spotted along the Hike-Bike Trail at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a female.

24 JUN 2016 | Huntley Meadows Park | Eastern Shieldback (female)

Editor’s Note: Thanks to Arthur V. Evans, a member of the BugGuide Facebook group, for identifying these specimens. Mr. Evans speculates the species of Eastern Shieldback featured in this post could be Protean Shieldback (Atlanticus testaceus).

Copyright © 2017 Walter Sanford. All rights reserved.

Great Spreadwing damselfly (male, grooming)

December 20, 2016

Great Spreadwing damselfly (Archilestes grandis) was spotted in the forest near a vernal pool at Huntley Meadows Park. This individual is the same male featured in my last blog post.

Before grooming

Look closely at the full-size version of the following photo. Notice the schmutz on the male damselfly’s abdomen, located near the right cercus of his terminal appendages.

11:09:41 a.m. EST

Grooming

A while later the male damselfly contorted himself into a position that looked like he was doing gymnastics. As it turns out, he was rubbing the tip of his abdomen against his thorax and legs in order to remove the schmutz.

11:31:09 a.m. EST

11:31:13 a.m. EST

11:31:18 a.m. EST

After grooming

Look closely at the full-size version of the following photo. Notice the schmutz on the male damselfly’s abdomen is gone. Soon afterward, the male flew in the direction of the vernal pool, presumably to look for female mates.

11:32:54 a.m. EST

Related Resource: Great Spreadwing damselflies (males, gymnasts) is a blog post by Walter Sanford that includes an embedded video showing similar grooming behaviors. The video features two segments: segment one shows the male damselfly grooming his legs; segment two shows the male grooming his wings by rubbing his abdomen against them.

Editor’s Note: If you check the EXIF for all five photos, then you will see the time stamp is one hour later than the times shown above. 06 November was the first time I used my camera since the end of Daylight Saving Time (at 2:00 a.m. the same day) — I forgot to reset the time in-camera!

Copyright © 2016 Walter Sanford. All rights reserved.

Tramea carolina exuvia

December 12, 2016

An exuvia from an unknown species of dragonfly was collected at Mason Neck West Park (MNWP), Fairfax County, Virginia USA. A two-step process was used to identify the genus and species of the specimen.

Family

First, determine the family of the specimen. For reference, watch the excellent Vimeo video, Identifying dragonfly larva to family (8:06).

The exuviae has a mask-like labium (not flat) with evenly-toothed crenulations, indicating this individual is a member of Family Libellulidae (Skimmers).

Genus and species

A dichotomous key was used to tentatively identify the exuvia as Carolina Saddlebags dragonfly (Tramea carolina), as indicated by the following morphological characteristics.

  • No dorsal hooks on any abdominal segments.
  • Lateral spines of abdominal segment nine (S9) are much longer than its mid-dorsal length. Lateral spines on segment eight (S8) are nearly as long as on segment nine (S9).
  • Superior abdominal appendage (epiproct) is shorter than inferior abdominal appendages (paraprocts).

Sincere thanks to Sue Gregoire, Kestrel Haven Migration Observatory, for verifying my preliminary observations and tentative identification!

No. 1

The specimen is approximately 2.4 cm (~0.9″) in length. Notice there are no dorsal hooks on any abdominal segments.

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

04 OCT 2016 | MNWP | Carolina Saddlebags (exuvia, dorsal-lateral view)

The white filaments that extend from the split in the thorax (as shown in Photo No. 1-2, 4-6) are breathing tubes, artifacts of the unique respiratory system of dragonfly nymphs.

No. 2

The eyes are rounded and widely separated. Notice the mask-like labium (sometimes referred to as “spoon-shaped”) with evenly-toothed crenulations along the margins between two lateral lobes.

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

04 OCT 2016 | MNWP | Carolina Saddlebags (exuvia, head-on view)

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

No. 3

A vertical white line marks the mid-dorsal length of abdominal segment nine (S9), as shown in the following annotated image; the vertical black line labeled “mid-dorsal length” is the same length as the white line. Notice the lateral spines of abdominal segment nine (S9) are much longer than its mid-dorsal length.

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

04 OCT 2016 | MNWP | Carolina Saddlebags (exuvia, anal pyramid view)

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

One of the keys to identifying skimmer dragonflies to the species level is to carefully examine the anal pyramid (S10), including the cerci (sing. cercus), epiproct, and paraprocts. Notice the epiproct is shorter than the paraprocts.

There is a lot of “seaweed” (aquatic vegetation) clinging to the exuvia, especially noticeable at the posterior end. Some collectors like to clean their specimens; I prefer to photograph them “as is.”

More photos of the exuvia are shown below.

No. 4

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

04 OCT 2016 | MNWP | Carolina Saddlebags (exuvia)

No. 5

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

04 OCT 2016 | MNWP | Carolina Saddlebags (exuvia)

No. 6

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

04 OCT 2016 | MNWP | Carolina Saddlebags (exuvia)

Tech Tips:

The following equipment was used to shoot the preceding photographs:

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resources:

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

Assuming the convention of labeling the two branches of each dichotomy as “a” and “b”, e.g. 1a, 1b, etc., a list of branches in the decision tree that I used to identify the genus of the dragonfly exuviae is as follows: 1b; 4b; 5b; 10a; 11b; 12b Tramea. A supplemental key featuring one dichotomy was used to identify the species: 1a carolina BINGO!

In long form, the decision tree is as follows:

p. 36, Key to the Genera of the Family Libellulidae
1b – Eyes lower, more broadly rounded and more lateral in position; abdomen usually ending more bluntly. [Go to] 4
4b – These appendages [inferior abdominal appendages (paraprocts)] straight or nearly so. [Go to] 5
5b – No dorsal hooks on any abdominal segments. [Go to] 10
10a – Lateral spines of segment 9 much longer than its mid dorsal length. [Go to] 11
11b – Lateral spines on 8 nearly as long as on 9. [Go to] 12
12b – Superior abdominal appendage (epiproct) shorter than inferiors [inferior abdominal appendages (paraprocts)]. Tramea BINGO!

p. 41, Key to the species of the genus Tramea
1a – Lateral spines of segment 8 directed straight to rearward; paraprocts longer than epiproct; two rows of spinules on upper surface of epiproct. carolina BINGO!

Copyright © 2016 Walter Sanford. All rights reserved.

Perithemis tenera exuviae

December 6, 2016

Several unknown dragonfly exuviae were collected from the Potomac River, Fairfax County, Virginia USA; two of the specimens are featured in this post. A two-step process was used to identify the genus and species of the specimens.

Family

First, determine the family of the specimens. For reference, watch the excellent Vimeo video, Identifying dragonfly larva to family (8:06).

The exuviae have a mask-like labium (not flat) with smooth crenulations, indicating these individuals are members of Family Libellulidae (Skimmers).

Genus and species

A dichotomous key was used to tentatively identify the exuviae as Eastern Amberwing dragonfly (Perithemis tenera), as indicated by the following morphological characteristics.

  • The cerci (sing. cercus) are slightly less than half the length of the paraprocts.
  • Dorsal hooks are clearly visible on abdominal segments four through nine (S4-9), plus a “nub” that is visible on segment three (S3).
  • Lateral spines are clearly visible on abdominal segments eight and nine (S8-9).

These specimens are the first odonate exuviae that I was able to identify to the species level. Sincere thanks to Sue Gregoire, Kestrel Haven Migration Observatory, for verifying my preliminary observations and tentative identification!

No. 1

Each specimen is approximately 1.4 cm (~0.6″) in length and approximately 0.6 cm (~0.2″) in maximum width. In Photo No. 1, the specimen shown on the left is an emergent nymph that was stuck in its exuvia.

A pair of Eastern Amberwing dragonfly (Perithemis tenera) exuviae collected from the Potomac River, Dyke Marsh Wildlife Preserve, Fairfax County, Virginia USA.

07 JUL 2016 | Potomac River | Eastern Amberwing (exuviae)

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

The white filaments that extend from the split in the thorax (as shown in Photo No. 1-3) are breathing tubes, artifacts of the unique respiratory system of dragonfly nymphs.

No. 2

An Eastern Amberwing dragonfly (Perithemis tenera) exuvia collected from the Potomac River, Dyke Marsh Wildlife Preserve, Fairfax County, Virginia USA.

07 JUL 2016 | Potomac River | Eastern Amberwing (exuvia, dorsal view)

No. 3

The eyes are relatively small and widely separated. Notice the mask-like labium (sometimes referred to as “spoon-shaped”) with smooth crenulations along the margins between two lateral lobes.

An Eastern Amberwing dragonfly (Perithemis tenera) exuvia collected from the Potomac River, Dyke Marsh Wildlife Preserve, Fairfax County, Virginia USA.

07 JUL 2016 | Potomac River | Eastern Amberwing (exuvia, head-on)

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

No. 4

One of the keys to identifying skimmer dragonflies to the species level is to carefully examine the anal pyramid (see S10, shown below), including the cerci (sing. cercus) and paraprocts. Notice the cerci are slightly less than half the length of the paraprocts.

An Eastern Amberwing dragonfly (Perithemis tenera) exuvia collected from the Potomac River, Dyke Marsh Wildlife Preserve, Fairfax County, Virginia USA.

07 JUL 2016 | Potomac River | Eastern Amberwing (exuvia, anal pyramid)

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

Tech Tips:

The following equipment was used to shoot the preceding photographs:

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resources:

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

Assuming the convention of labeling the two branches of each dichotomy as “a” and “b”, e.g. 1a, 1b, etc., a list of branches in the decision tree that I used to identify the species of the dragonfly exuviae is as follows: 1b; 4b; 5a; 6a BINGO!

In long form, the decision tree is as follows:

p. 36, Key to the Genera of the Family Libellulidae
1b – Eyes lower, more broadly rounded and more lateral in position; abdomen usually ending more bluntly. [Go to] 4
4b – These appendages [inferior abdominal appendages (paraprocts)] straight or nearly so. [Go to] 5
5a – Dorsal hooks on some abdominal segments. [Go to] 6
6a – Dorsal hook on 9. Perithemis (One species, Perithemis tenera.) BINGO!

Copyright © 2016 Walter Sanford. All rights reserved.


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