Posts Tagged ‘subgenital plate’

Arrowhead Spiketail dragonfly (female)

May 27, 2019

An Arrowhead Spiketail dragonfly (Cordulegaster obliqua) was spotted in a sunny clearing along a small forest stream at an undisclosed location in Prince William County, Virginia USA.

21 MAY 2019 | PNC. William County, VA | Arrowhead Spiketail (female)

This individual is a female, as indicated by her rounded hind wings, terminal appendages, and prominent ovipositor at the tip of her abdomen.

[Females in the Family Cordulegastridae (Spiketails) feature a] …pointed and spikelike (thus the group name) ovipositor, really a “pseudo-ovipositor” formed from the prolonged subgenital plate. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 7005-7006). Princeton University Press. Kindle Edition.

21 MAY 2019 | PNC. William County, VA | Arrowhead Spiketail (female)

Although the pattern of arrowhead-shaped markings visible on the dorsal side of her abdomen is unmistakeable, notice that the thorax features two stripes. The latter field mark can be used to differentiate spiketails from cruisers that have one stripe on their thorax.

21 MAY 2019 | PNC. William County, VA | Arrowhead Spiketail (female)

Mike Powell and I have photowalked together so many times that we are comfortable working cooperatively to shoot a subject. I wanted to get a shot of the face of the Arrowhead Spiketail but was concerned it would spook the dragonfly if I were to get “up in her grill.” So I waited until Mike had taken all of the photographs he wanted before approaching the dragonlfy for her “beauty shot.” As it turns out, the model was extraordinarily tolerant and didn’t fly away until sometime after Mike and I moved on to the next site.

21 MAY 2019 | PNC. William County, VA | Arrowhead Spiketail (female)

Notice the interrupted fern (Osmunda claytoniana) that appears in the background of every photo of the Arrowhead Spiketail.

Location, location, location.

Some species of odonates are habitat generalists, meaning they can be found almost anywhere there is water.

Habitat-specific odonates can be found only in specific habitats — for these species, finding them is all about location, location, location. Arrowhead Spiketail dragonflies are habitat-specialists.

Habitat: Small swift streams and soft-bottomed muddy seeps in forest, also streams reduced to series of small pools during drier weather. As in some other spiketails, skunk cabbage often present. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 7081-7082). Princeton University Press. Kindle Edition.

Skunk cabbage (Symplocarpus foetidus) and interrupted fern (Osmunda claytoniana) were observed growing in a seep located between a dirt trail and the small stream where the Arrowhead Spiketail was spotted — the perfect place for several species of habitat-specific odonates!

The last photo shows the clearing along a small forest stream where several species of dragonflies were spotted, including the Arrowhead Spiketail featured in this blog post. The stream is no more than a few feet wide and only a few inches deep in most places.

The small stream where several species of dragonflies were spotted.

The backstory

Telephoto lenses can cause a type of distortion called “foreshortening,” as seen in the preceding photo. Mike Powell and I were standing at the edge of the stream bank trying to decide whether we wanted to go down the short, steep slope to explore the clearing when we spotted a large UFO, that is, an “Unidentified Flying Odonate.” Mike and I took “record shots” of the dragonfly; looking at the LCD of our cameras, we identified the UFO as a Gray Petaltail dragonfly (Tachopteryx thoreyi).

Mike and I had seen a Gray Petaltail at another location (near the beginning of our photowalk), but we were unable to photograph it. So down the bank we went! As it turns out, there were at least two Grays in the meadow: a female; and a male. As Mike was photographing one of the Gray Petaltails he noticed another “large dragonfly.” As we slowly moved closer to the new unknown dragonfly, I quickly realized Mike had spotted an Arrowhead Clubtail. Great catch, Mike!

Please see Female Arrowhead Spiketail dragonfly for Mike’s take on our shared experience.

Uncommon

Arrowhead Spiketail is classified as an uncommon species of odonate. The following map shows all official records for Arrowhead Clubtail (C. obliqua) in the United States of America.

DSA Distribution Viewer | Arrowhead Spiketail

Source Credit: Abbott, J.C. 2006-2019. OdonataCentral: An online resource for the distribution and identification of Odonata. Available at http://www.odonatacentral.org. (Accessed: May 27, 2019).

Key: blue dots = Dot Map Project; green dots = Accepted records; yellow dots = Pending records.

Our spotting of Arrowhead Spiketail is a new DSA record for Prince William County, Virginia.

Adult flight period

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 C. obliqua is 11 May to 17 July. The species is classified as uncommon. Its habitat is “small streams.”

Bear in mind, Dr. Roble’s records are for the entire state, therefore the adult flight period for C. obliqua seems to be longer than it is in reality. The adult flight period for a single site is probably shorter — more likely around one month. For example, according to records for Northern Virginia maintained by Kevin Munroe, former manager of Huntley Meadows Park, the adult flight period for Arrowhead is 28 May to 27 June (peaks in June).

Copyright © 2019 Walter Sanford. All rights reserved.

 

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Mocha Emerald terminal appendages (female)

September 29, 2017

Mocha Emerald dragonfly (Somatochlora linearis) was spotted by Andrew Rapp in Henrico County, Virginia USA. This individual is a female.

Terminal appendages

All female dragonflies have a pair of cerci (superior appendages) that have little or no function. The hind wings of female Mocha Emerald dragonflies are rounded.

21 JUL 2017 | Henrico County, VA | Mocha Emerald (female)

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

21 JUL 2017 | Henrico County, VA | Mocha Emerald (female)

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

Notice the subgenital plate shown in the preceding photo.

subgenital plate: plate below S8 that holds bunches of eggs when enlarged; variable enough in shape to be of value in identification. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 11723-11724). Princeton University Press. Kindle Edition.

“S8” refers to abdominal segment eight. Remember that all dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back.

Oviposition (egg-laying)

The following Apple iPhone 3GS “raw” video clip shows a female Mocha Emerald dragonfly laying eggs by the process of oviposition. The process typically lasts a few seconds to a few minutes. This individual was spotted on 16 July 2011 during a photowalk through the “Wildlife Sanctuary,” one of seven small parks in the community of Hollin Hills, Fairfax County, Virginia USA.

Mocha Emerald dragonfly (female, ovipositing) [Ver. 2] (0:23)

Related Resource: Mocha Emerald terminal appendages (male).

Editor’s Note: Sincere thanks to Andrew Rapp for permission to use his still photographs.

Copyright © 2017 Walter Sanford. All rights reserved.

Cobra Clubtail external reproductive anatomy

May 28, 2017

I liked to make paper- and plastic models when I was a child. Seems like the directions for assembling many models — not that anyone reads the directions — always started by saying something like “Insert Tab A in Slot B.”

Oddly enough, that line reminds me of how odonates copulate, in general, and Cobra Clubtail dragonflies (Gomphurus vastus) in particular.

Male

The hamules are “Tab A.”

Female

The subgenital plate is “Slot B.”

Putting it all together

Insert Tab A in Slot B. That’s the PG-rated version of how Cobra Clubtail dragonflies copulate in order to reproduce.

The Backstory

There is an annual mass emergence of Cobra Clubtails during the first week-or-two of May at Riverbend Park. It’s a spectacular event worth seeing firsthand!

The following photo shows a dead female, one of several Cobra Clubtails that were trampled by groups of elementary school children visiting the park on 09 May 2017. Her premature death saddens me because it was avoidable — the students should have been warned to watch their step because there were lots of Cobra Clubtails perching on the ground almost everywhere.

In the hope the female didn’t die in vein, I reluctantly decided to photograph the corpse in order to illustrate her external reproductive anatomy.

Editor’s Note: Sincere thanks to Dennis Paulson for help in identifying the female parts on the ventral side of abdominal segments eight and nine (S8-9).

Copyright © 2017 Walter Sanford. All rights reserved.

Common Baskettail (terminal appendages)

May 18, 2017

A male and female Common Baskettail dragonfly (Epitheca cynosura) were spotted recently at the same location in Fairfax County, Virginia USA.

Male and female Common Baskettails look similar. Terminal appendages can be used to identify gender.

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”).

03 MAY 2017 | Fairfax County, VA | Common Baskettail (male)

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

Female

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

03 MAY 2017 | Fairfax County, VA | Common Baskettail (female)

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

A better view of the subgenital plate is provided by the following digital scan of the underside of the abdomen of a female Common Baskettail. The subgenital plate looks a little like a pair of calipers. Also known as vulvar lamina, the subgenital plate is located under the ninth abdominal segment (S9) of some female odonates and “serves to hold eggs in place during exophytic oviposition.” Remember that all dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back.

Image used with permission from Ed Lam.

Copyright © 2017 Walter Sanford. All rights reserved.

Autumn Meadowhawks (males and females)

November 5, 2015

Autumn Meadowhawk (Sympetrum vicinum) is a member of the Skimmer Family of dragonflies that is commonly spotted during the fall months at many water bodies in the mid-Atlantic United States, such as the vernal pools and central wetland area at Huntley Meadows Park.

The first individual is a male, as indicated by its coloration and terminal appendages. By the first week in November, fall foliage is past peak color and the ground is covered almost completely by leaf litter.

An Autumn Meadowhawk dragonfly (Sympetrum vicinum) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a male.

04 NOV 2015 | Huntley Meadows Park | Autumn Meadowhawk (male)

The following photo shows another male, spotted a couple of weeks earlier.

An Autumn Meadowhawk dragonfly (Sympetrum vicinum) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a male.

21 OCT 2015 | Huntley Meadows Park | Autumn Meadowhawk (male)

The next Autumn Meadowhawk is a female, as indicated by its coloration and terminal appendages. Female abdomens are slightly thicker than those of males and noticeably flared toward both the thorax and tip of the abdomen. The “subgenital plate,” located under the ninth abdominal segment (S9), is a large scoop-like structure used for laying eggs (exophytic oviposition).

An Autumn Meadowhawk dragonfly (Sympetrum vicinum) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a female.

15 OCT 2015 | Huntley Meadows Park | Autumn Meadowhawk (female)

The last individual is another female. Regular readers of my photoblog know I’m especially fond of head-tilts in which the dragonfly seems to display some of its personality.

An Autumn Meadowhawk dragonfly (Sympetrum vicinum) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a female.

15 OCT 2015 | Huntley Meadows Park | Autumn Meadowhawk (female)

Copyright © 2015 Walter Sanford. All rights reserved.

What was your first clue?

April 27, 2015

I have photographed relatively few members of the Emerald Family of dragonflies. After tentatively identifying the following individual as a female Common Baskettail (Epitheca cynosura), I consulted the experts of the Northeast Odonata Facebook group for verification: I was fairly certain of the species; less certain of the gender.

Experienced odonate hunters like Chris Hill and Ed Lam looked at the specimen and quickly recognized its gender, as indicated by the cerci (terminal appendages) and thickness of its abdomen. In contrast, I haven’t seen enough baskettails to feel comfortable using those field markers to identify the gender.

So you may be wondering, “What was your first clue this individual is a female?” In a word (well, two) its subgenital plate, as shown in the following annotated image.

A Common Baskettail dragonfly (Epitheca cynosura) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a female.

24 APR 2015 | Huntley Meadows Park | Common Baskettail (female)

A better view of the subgenital plate is provided by the following digital scan of the underside of the abdomen of a female Common Baskettail. The subgenital plate looks a little like a pair of calipers. Also known as vulvar lamina, the subgenital plate is located under the ninth abdominal segment (S9) of some female odonates and “serves to hold eggs in place during exophytic oviposition.” Remember that all dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back.

11161355_10206237290082057_635765194893154908_n

Image used with permission from Ed Lam.

Related Resource: Common Baskettail dragonfly (male) – a tutorial illustrating male reproductive anatomy.

Editor’s Note: Special thanks to Chris Hill and Ed Lam, members of the Northeast Odonata Facebook group, for kindly confirming my tentative identification of the gender of this specimen and for teaching me about the subgenital plate (a.k.a., vulvar lamina) — a feature that I misidentified as an “ovipositor” in my initial post to the group.

Copyright © 2015 Walter Sanford. All rights reserved.

Eastern Pondhawk dragonflies (females)

August 10, 2014

Eastern Pondhawk dragonfly (Erythemis simplicicollis) is another species of dragonfly with prominent pseudopupils, as shown by several specimens spotted during a photowalk at Huntley Meadows Park on 22 July 2014.

Eastern Pondhawk dragonfly (female)

These individuals are females, as indicated by their green coloration and white terminal appendages. See Eastern Pondhawk dragonflies, a photo-illustrated guide to the identification of male- and female terminal appendages.

Eastern Pondhawk dragonfly (female)

Look closely at the following photo. Notice the subgenital plate, a black “shark fin” located beneath segment eight of the abdomen.

Underneath Segment 8 there is either an ovipositor or a subgenital plate, depending upon the species [of dragonfly]. Both structures are for laying eggs and extend over Segment 9 and possibly beyond. Source Credit: Dragonflies of the North Woods, by Kurt Mead.

Remember that “Segment 8 and 9″ refers to abdominal segments eight and nine (of 10), numbered from front to back. Digital Dragonflies features a side view of a female Eastern Pondhawk in which the subgenital plate is shown clearly.

Eastern Pondhawk dragonfly (female)

Related Resources: Digital Dragonflies, presenting high-resolution digital scans of living dragonflies.

  • Genus Erythemis |Erythemis simplicicollis | Eastern Pondhawk | female | top view
  • Genus Erythemis |Erythemis simplicicollis | Eastern Pondhawk | female | side view
  • Genus Erythemis |Erythemis simplicicollis | Eastern Pondhawk | male | top view
  • Genus Erythemis |Erythemis simplicicollis | Eastern Pondhawk | male | side view

Copyright © 2014 Walter Sanford. All rights reserved.

Brown Spiketail dragonfly (female)

May 26, 2013

The following photo gallery shows a female Brown Spiketail dragonfly (Cordulegaster bilineata) spotted on 09 May 2013, perching near the ground in an open field along the trail to Hidden Pond, a small lake located at Meadowood Recreation Area in Fairfax County, Virginia USA.

Why are Spiketail dragonflies called “spiketails,” and what field markers can be used to identify this individual as a female? The answer to both questions is illustrated in the following annotated close-up photograph of the posterior end of the Brown Spiketail dragonfly’s abdomen.

Brown-Spiketail_f_anatomy

All female dragonflies have a pair of cerci (superior appendages) that have little or no function. Notice the spike-shaped subgenital plate.

Spiketail dragonflies are so named because the female’s long [subgenital plate], or egg-laying organ, extends beyond the tip of the abdomen. Source Credit: New York State Department of Environmental Conservation.

Thanks to Richard Orr, renowned expert on dragonflies and damselflies of the mid-Atlantic region, for verifying my tentative indentification of both the gender of the dragonfly and some of its anatomical parts.

Related Resources: Odonate Terminal Appendages.

Copyright © 2013 Walter Sanford. All rights reserved.

Eastern Pondhawk dragonflies (females)

August 12, 2012

The following photographs show a couple of female Eastern Pondhawk dragonflies (Erythemis simplicicollis) spotted in a meadow located at least 100 yards from the central wetland area at Huntley Meadows Park.

Notice the subgenital plate, a black “shark fin” located beneath segment eight of the abdomen.

Underneath Segment 8 there is either an ovipositor or a subgenital plate, depending upon the species [of dragonfly]. Both structures are for laying eggs and extend over Segment 9 and possibly beyond. Source Credit: Dragonflies of the North Woods, by Kurt Mead.

Remember that “Segment 8 and 9” refers to abdominal segments eight and nine (of 10), numbered from front to back.

P1110155-rw2-ver2_apertureP1110220-rw2-ver2_apertureP1110226-rw2-ver2_aperture

Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com


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