Posts Tagged ‘Mason Neck West Park’

Pop quiz answer key

June 9, 2017

Perhaps the simplest way to provide answers to the recent pop quiz — in which readers were challenged to identify the gender of two Southern Spreadwing damselflies (Lestes australis) — is to show what the teneral/immature male (shown in my last post) will look like when he’s a little older.

The following photos show Southern Spreadwings spotted at Mason Neck West Park, Fairfax County, Virginia USA. Both individuals are male, as indicated by their terminal appendages and blue coloration.

Both photographs of the male Southern Spreadwings were taken at an angle that shows their terminal appendages clearly.

All male damselflies have four terminal appendages, collectively called “claspers.” Male damselfly terminal appendages don’t look exactly the same for all species of damselflies, but their function is identical. Claspers are used to grab and hold female damselflies during mating: an upper pair of cerci (“superior appendages”) and a lower pair of paraprocts (“inferior appendages”).

In contrast, female damselflies have two cerci (sing. cercus), superior appendages that have little or no function. Notice the two “nubs” at the tip of the abdomen, as shown in the photo of the female Southern Spreadwing that was featured in the pop quiz.

Editor’s Notes: There are five families of damselflies (Suborder Zygoptera) in the United States of America, although only three families occur in the mid-Atlantic region: Family Calopterygidae (Broad-winged Damselflies)Family Coenagrionidae (Narrow-winged Damselflies); and Family Lestidae (Spreadwings).

Male Broad-winged Damselflies and Spreadwing Damselflies have terminal appendages that are large enough to see with the unaided eye. Generally speaking, both male and female Narrow-winged Damselflies are too small to see their terminal appendages clearly in most photographs.

Copyright © 2017 Walter Sanford. All rights reserved.

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Pop quiz

June 7, 2017

OK, it’s time to assess what you’ve learned about damselflies by following my blog.

Two Southern Spreadwing damselflies (Lestes australis) were photographed on the same day at the same location. Both damselflies are teneral/immature, that is, they are relatively young. One is a female; one is a male. Can you identify the gender of the damselflies shown in the following photos?

I’ll give you a hint: Examine their terminal appendages by looking at the full-size version of both photos.

No. 1

No. 2

Editor’s Note: The answer key will be published in my next post.

Copyright © 2017 Walter Sanford. All rights reserved.

Voltinism, revisited

April 30, 2017

Voltinism is a term used in biology to indicate the number of broods or generations of an organism in a year. Source Credit: Wikipedia.

Some species of odonates, such as Southern Spreadwing damselfly (Lestes australis), can be multivoltine.

Huntley Meadows Park

Long-term monitoring of a vernal pool at Huntley Meadows Park has shown Southern Spreadwing is multivoltine at that site.

Mason Neck West Park

Males and females from a single brood of Southern Spreadwing were observed during Fall 2016 at Mason Neck West Park; males from another brood were spotted at the same location on 05 April 2017 and again on 18 April 2017. This evidence suggests Southern Spreadwing is multivoltine at Mason Neck West Park (MNWP). Further field observations are necessary to determine whether more than two broods occur at this location.

This individual is a male, as indicated by his coloration and terminal appendages.

Please look at the full-size versions of the preceding photos in order to appreciate the “fresh” coloration that seems to be a noticeable characteristic for many species of recently-emerged odonates.

Copyright © 2017 Walter Sanford. All rights reserved.

Acceptable uncertainty

February 23, 2017

An unknown species of damselfly from the Family Coenagrionidae (Narrow-winged Damselflies) was spotted at the stormwater management pond located at Mason Neck West Park. This individual is a female, as indicated by her terminal appendages.

I thought the damselfly might be a mature female Rambur’s Forktail damselfly (Ischnura ramburii), based upon the fact that I’d seen an immature female Rambur’s Forktail on 03 October 2016 at the same location. I consulted the experts of the Northeast Odonata Facebook group for verification of my tentative identification.

It’s a female bluet, probably Familiar [Bluet] but it has a hint of a carina, so it might be Big [Bluet], but the eyespots look more like Familiar. Female Rambur’s does not have shoulder stripes. Source Credit: Dr. Michael Moore. Michael is an active contributor to the Dragonfly and Damselfly Field Guide and ID App.

Difficult though it may be for me to accept, sometimes it’s impossible to identify odonates with certainty based upon a single photograph. This is especially true for many species of female damselflies.

Copyright © 2017 Walter Sanford. All rights reserved.

Peopoll’s Choice Awards – Top 10 Photos of 2016

January 22, 2017

Ladies and gentlemen, the people have spoken. It’s time to announce the winners of the Peopoll’s Choice Awards for my Top 10 Photos of 2016. The Top 10 photos were selected using reader feedback. Sincere thanks for your participation!

Award-winning photos are presented in order of most-to-least votes. I cast the tie-breaking votes for the last four winners (No. 7-10), chosen from five photos that received the same number of your votes. In other words, I selected one of five photos to omit.

No. 1

No. 2

No. 3

No. 4

No. 5

No. 6

No. 7

No. 8

No. 9

No. 10

Editor’s Note: The following location codes are used in some photo captions, shown above.

Copyright © 2017 Walter Sanford. All rights reserved.

Top 10 Photos of 2016

December 30, 2016

The following gallery shows 33 finalists for my “Top 10 Photos of 2016.” The photos are presented in reverse-chronological order beginning in December 2016 and ending in May 2016.

The Top 10 photos will be selected using reader feedback. Please enter a comment at the end of this post listing the number for each of your 10 favorite photos. If listing 10 photos is asking too much, then please list at least five photos, e.g., No. 5, 8, 14, 17, 21, etc. Thanks for sharing your selections, and thanks for following my photoblog!

No. 1

The following specimen was collected on 16 May 2016 (with permission from park staff) along the Potomac River at Riverbend Park, Fairfax County, Virginia USA. (This studio photograph, taken on 25 December 2016, hasn’t been published in a post.)

No. 2

The next specimen was collected on 07 July 2016 along the Potomac River in Fairfax County, Virginia USA. (This studio photograph was taken on 02 December 2016.)

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)

No. 3

No. 4

A Shadow Darner dragonfly (Aeshna umbrosa) spotted at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a female heteromorph.

14 OCT 2016 | JMAWR | Shadow Darner (female heteromorph)

No. 5

No. 6

No. 7

No. 8

No. 9

No. 10

No. 11

No. 12

No. 13

No. 14

No. 15

No. 16

No. 17

No. 18

No. 19

No. 20

No. 21

No. 22

No. 23

No. 24

No. 25

No. 26

No. 27

A mating pair of Slender Spreadwing damselflies (Lestes rectangularis) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This pair is "in heart."

24 JUN 2016 | HMP | Slender Spreadwing (mating pair, “in heart“)

No. 28

No. 29

No. 30

No. 31

No. 32

No. 33

Editor’s Note: The following location codes are used in some photo captions, shown above.

Copyright © 2016 Walter Sanford. All rights reserved.

Rambur’s Forktail damselfly (female)

December 16, 2016

A Rambur’s Forktail damselfly (Ischnura ramburii) was spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is an immature heteromorph female, as indicated by the reddish-orange coloration of her thorax and abdominal segments one and two (S1-2), and reddish-orange postocular spots; her coloration will become duller as she matures. Andromorph females are colored like males.

A Rambur's Forktail damselfly (Ischnura ramburii) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is an immature heteromorph female.

03 OCT 2016 | Mason Neck West Park | Rambur’s Forktail (female)

This sighting was another reminder of one of many Walterisms: Don’t be dismissive! Huh? Male Rambur’s Forktail damselflies look similar to male Eastern Forktail damselflies (Ischnura verticalis). Eastern Forktails are relatively common, especially during spring and early-summer. Common. That’s the key word. When I noticed several male Rambur’s Forktails at the water retention pond I thought, “Oh, Eastern Forktails. Nothing to see here, folks. Move along.” Fortunately I spotted the immature heteromorph female and realized the error of my ways.

I’ll say it again: Don’t be dismissive — that kind of thinking can result in missed opportunities for wildlife photographers. I never expected to see Rambur’s Forktails at Mason Neck West Park and my preconceptions almost caused me to miss a golden opportunity to see a relatively uncommon damselfly.

Related Resources: Excellent digital scans created by Gayle and Jeanelle Strickland. Click on the button labeled “Download file” in order to view full-size version of the graphics.

  • Ischnura ramburii female #2 | heteromorph female | JPG
  • Ischnura ramburii female #8 | andromorph female | JPG
  • Ischnura ramburii male #2 | male | JPG

Copyright © 2016 Walter Sanford. All rights reserved.

Wandering Glider dragonfly (male)

December 14, 2016

Wandering Glider dragonfly (Pantala flavescens) was spotted at Mason Neck West Park (MNWP), Fairfax County, Virginia USA. This individual is a male. Wandering Gliders do not display sexual dimorphism; terminal appendages may be used to differentiate females and males.

A Wandering Glider dragonfly (Pantala flavescens) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is a male.

04 OCT 2016 | Mason Neck West Park | Wandering Glider (male)

I like the subtle beauty of the coloration/pattern of markings along the abdomen of Wandering Gliders.

A Wandering Glider dragonfly (Pantala flavescens) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is a male.

04 OCT 2016 | Mason Neck West Park | Wandering Glider (male)

This guy was very skittish! I spooked him when I backed up for a slightly wider view of the scene — usually that happens the other way around.

Copyright © 2016 Walter Sanford. All rights reserved.

Tramea carolina exuvia

December 12, 2016

An exuvia from an unknown species of dragonfly was collected on 04 October 2016 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). [See Photo No. 2.]

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).[See Photo No. 3.]
  • Superior abdominal appendage (epiproct) is shorter than inferior abdominal appendages (paraprocts). [See Photo No. 3.]

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.

No. 1 | Carolina Saddlebags (Tramea carolina) | exuvia (dorso-lateral)

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.

No. 2 | Carolina Saddlebags (Tramea carolina) | exuvia (face-head)

(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.

No. 3 | Carolina Saddlebags (Tramea carolina) | exuvia (anal pyramid)

(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.

No. 4 | Carolina Saddlebags (Tramea carolina) | exuvia (dorsal)

No. 5

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

No. 5 | Carolina Saddlebags (Tramea carolina) | exuvia (face-head)

No. 6

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

No. 6 | Carolina Saddlebags (Tramea carolina) | exuvia (anal pyramid)

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.

Southern Spreadwing at MNWP

November 19, 2016

Many Southern Spreadwing damselflies (Lestes australis) were observed around the stormwater management pond located at Mason Neck West Park (MNWP) during Fall 2016. The following gallery, presented in chronological order, showcases select specimens spotted during several photowalks at the park.

The first individual is a female, as indicated by her coloration and terminal appendages.

A Southern Spreadwing damselfly (Lestes australis) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is a female.

27 SEP 2016 | MNWP | Southern Spreadwing (female)

The next two photos show a couple of males, as indicated by their coloration and terminal appendages.

A Southern Spreadwing damselfly (Lestes australis) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is a male.

27 SEP 2016 | MNWP | Southern Spreadwing (male)

A Southern Spreadwing damselfly (Lestes australis) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is a male.

27 SEP 2016 | MNWP | Southern Spreadwing (male)

The following photo shows a mating pair “in tandem,” the post-copulatory phase when the male guides the female to egg-laying sites. The male is on top; the female on the bottom.

A mating pair of Southern Spreadwing damselflies (Lestes australis) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This pair is in tandem.

27 SEP 2016 | MNWP | Southern Spreadwing (mating pair, in tandem)

The female uses her ovipositor to insert eggs into vegetation (endophytic oviposition).

A mating pair of Southern Spreadwing damselflies (Lestes australis) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This pair is in tandem; the female is laying eggs (oviposition).

27 SEP 2016 | MNWP | Southern Spreadwing (mating pair, in tandem)

More males were spotted on consecutive days in early-October.

A Southern Spreadwing damselfly (Lestes australis) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is a male.

03 OCT 2016 | MNWP | Southern Spreadwing (male)

A Southern Spreadwing damselfly (Lestes australis) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is a male.

04 OCT 2016 | MNWP | Southern Spreadwing (male)

The last individual is a female that I found resting/roosting in a field of grasses, quite a distance from the water. As it turns out, this female — spotted on 14 October 2016 — is also the last Southern Spreadwing observed at Mason Neck West Park during 2016. It’s worth noting the late-date for Southern Spreadwing at MNWP is consistent with the late-date of 15 October 2015 for the same species at Huntley Meadows Park.

A Southern Spreadwing damselfly (Lestes australis) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is a female.

14 OCT 2016 | MNWP | Southern Spreadwing (female)

A Southern Spreadwing damselfly (Lestes australis) spotted at Mason Neck West Park, Fairfax County, Virginia USA. This individual is a female.

14 OCT 2016 | MNWP | Southern Spreadwing (female)

Copyright © 2016 Walter Sanford. All rights reserved.


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