Posts Tagged ‘Occoquan Bay National Wildlife Refuge’

The ugly side of Mother Nature

October 1, 2017

A Big Bluet damselfly (Enallagma durum) was spotted during a photowalk along Deephole Point Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. This individual is a male, eating a teneral damselfly.

10 SEP 2017 | Occoquan Bay NWR | Big Bluet (male, eating prey)

I think they may both be Big Bluets. Source Credit: Michael Moore, Virginia Odonata Facebook group.

Some species of odonates are cannibals, that is, they feed on their own species. And there it is — the ugly side of Mother Nature!

Copyright © 2017 Walter Sanford. All rights reserved.

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Great Blue Skimmer (mature females)

September 27, 2017

Two Great Blue Skimmer dragonflies (Libellula vibrans) were photographed during photowalks at Occoquan Bay National Wildlife Refuge (OBNWR), Prince William County, Virginia USA.

Both individuals are mature female, as indicated by their terminal appendages, muted coloration, and tattered wings. They were perching in shady hidey-holes relatively far from water.

Female Great Blue Skimmers have a pair of flanges beneath their eighth abdominal segment that are used to scoop and hold a few drops of water when laying eggs (oviposition), hence the family name “Skimmer.” Remember that all dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back.

Copyright © 2017 Walter Sanford. All rights reserved.

Needham’s Skimmer (mature females)

September 25, 2017

In my experience, female Needham’s Skimmer dragonflies (Libellula needhami) seem to be more abundant than males toward the end of the adult flight period for that species.

Two Needham’s Skimmers were photographed during photowalks at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. Both individuals are mature female, as indicated by their terminal appendages and muted coloration.

Post Update: Sincere thanks to Drew Chaney for identifying the flowering plant shown in the preceding photo. According to Drew, “It’s either Clematis terniflora or virginiana. I can’t tell without leaves: Terniflora has entire leaves; virginiana has toothed ones.”

Copyright © 2017 Walter Sanford. All rights reserved.

Fine-lined Emerald dragonfly redux (Part 1)

September 19, 2017

Several Fine-lined Emerald dragonflies (Somatochlora filosa) were spotted during a photowalk at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

The same dragonfly was photographed while it perched in several shady places along one of the trails at the park. In my limited experience, Somatochlora filosa seems to prefer perching on bare tree branches or long stems of wild grass. Part 1 features two photo sets showing Fine-lined Emerald resting on other types of perches; Part 2 will feature two more photo sets showing the dragonfly perching on grasses.

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

Set 1

The first photograph is a strong contender for my Odonart Portfolio. I like the way the green vegatation complements the dragonfly’s emerald colored eyes. Can anyone identify the type of plant on which the dragonfly is perching?

Post Update: Sincere thanks to Drew Chaney for identifying the green plant shown in the preceding photo. According to Drew, “It’s common evening-primrose, probably Oenothera biennis.”

Set 2

The second set of photos shows the dragonfly perching on a Common Milkweed (Asclepias syriaca) seed pod.

The next photo was taken a step-or-so closer…

This individual has a distinctive eye injury to the top of his left eye (facing forward).

And after a few side steps, I was able to take a good ventral-lateral shot.

Editor’s Note: Sincere thanks to several members of the Capital Naturalist Facebook group for identifying the species of milkweed plant shown in photo Set 2. “Capital Naturalist” is administered by Alonso Abugattas, Natural Resources Manager, Arlington County Parks, Virginia.

Related Resources

Copyright © 2017 Walter Sanford. All rights reserved.

Robber fly (female)

September 17, 2017

An unknown species of robber fly was spotted perching on a wooden post along Deephole Point Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. Notice its abdomen is two-thirds striped and one-third black, indicating this individual is a female.

10 SEP 2017 | Occoquan Bay NWR | robber fly (female)

Copyright © 2017 Walter Sanford. All rights reserved.

Black Saddlebags (terminal appendages)

September 15, 2017

Male and female Black Saddlebags dragonflies (Tramea lacerata) are somewhat similar in appearance. Terminal appendages can be used to identify gender.

Female

A female Black Saddlebags was spotted along Deephole Point Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

10 SEP 2017 | Occoquan Bay NWR | Black Saddlebags (female)

Female dragonflies have a pair of cerci (superior appendages) that have little or no function.

10 SEP 2017 | Occoquan Bay NWR | Black Saddlebags (female)

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

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”).

A male Black Saddlebags was spotted in the central wetland area at Huntley Meadows Park, Fairfax County, Virginia USA.

12 SEP 2014 | Huntley Meadows Park | Black Saddlebags (male)

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

Copyright © 2017 Walter Sanford. All rights reserved.

Fine-lined Emerald dragonflies (males)

September 13, 2017

Three Fine-lined Emerald dragonflies (Somatochlora filosa) were spotted during a long photowalk at Occoquan Bay National Wildlife Refuge. All three individuals are males, as indicated by their terminal appendages and prominent hamules.

If I have seen further it is by standing on the shoulders of giants. Source Credit: Sir Isaac Newton.

Sincere thanks to Jim Waggener, Wildlife Survey Coordinator for The Audubon Society of Northern Virginia, as well as other members of Jim’s survey group for sharing information that enabled me to find this rare to uncommon species of dragonfly. The group has surveyed four sites in Northern Virginia regularly for many years, including Occoquan Bay National Wildlife Refuge.

No. 1

Fine-lined Emerald dragonflies seem to prefer perching on bare tree branches or long stems of wild grass, typically at chest- or head-height although not exclusively. For example, this guy was perched about waist-high on a cluster of fallen tree branches.

10 SEP 2017 | Occoquan Bay NWR | Fine-lined Emerald (male)

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

Fine-lined Emerald seems to prefer perching in sun rather than shade, unlike Mocha Emerald (Somatochlora linearis) — another species from the Family Corduliidae (Emeralds) found in Northern Virginia that prefers shady places.

The following ventral-lateral shot shows the lines on the thorax for which this species is named.

10 SEP 2017 | Occoquan Bay NWR | Fine-lined Emerald (male)

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

No. 2

The male shown in the next photo is perched on a long grass stem, about chest-high. He posed for two shots, patrolled back-and-forth a few times, and then disappeared.

10 SEP 2017 | Occoquan Bay NWR | Fine-lined Emerald (male)

No. 3

The last male was the most cooperative model. The first photo was taken at a distance of approximately six feet.

10 SEP 2017 | Occoquan Bay NWR | Fine-lined Emerald (male)

The next photo was taken a step-or-so closer…

10 SEP 2017 | Occoquan Bay NWR | Fine-lined Emerald (male)

And after a few side steps, I was able to take a good lateral shot.

10 SEP 2017 | Occoquan Bay NWR | Fine-lined Emerald (male)

The Backstory

This might be one of those stories in which the take-away is “persistence pays dividends.”

I made two trips to Occoquan Bay NWR during Fall 2016 when Fine-lined Emerald was my target species. On 21 September 2016, I spotted one or more dragonflies (species unknown) patrolling the treetops along one of the trails at OBNWR. I didn’t see any signs of Fine-lined Emerald on 25 October 2016, consistent with records for late-date maintained by Kevin Munroe (04 October for Northern Virginia) and Dr. Steven Roble (15 October for the Commonwealth of Virginia).

In retrospect, I realized I started searching too late in the year during 2016 so I started earlier in 2017. My first trip to OBNWR was on 30 August 2017; it turned out to be fruitless. I hit the jackpot on 10 September 2017! Fine-lined Emerald is a new species for my life list of dragonflies.

Rare to Uncommon

A distribution map of official records for Fine-lined Emerald helps to illustrate its classification as a rare to uncommon species of odonate.

Source Credit: Abbott, J.C. 2006-2017. OdonataCentral: An online resource for the distribution and identification of Odonata. Available at http://www.odonatacentral.org. (Accessed: September 14, 2017).

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

Related Resources

Copyright © 2017 Walter Sanford. All rights reserved.

Black Swallowtail (Papilio polyxenes)

September 5, 2017

Several Black Swallowtail butterflies (Papilio polyxenes) were spotted on 30 August 20017 during a photowalk along Deephole Point Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

The following individual is a male. All of the Black Swallowtails that I observed seemed to be quite skittish, including this guy. He flew away every time I approached him slowly. I noticed that he returned to nearly the same spot after a lot of fluttering around, so I moved to a position from which I could shoot his photo without moving.

108mm (600mm, 35mm equivalent) | ISO 100 | f/8 | 1/800s | -3 ev

Exposure Compensation

Exposure compensation is your friend when shooting high-contrast subjects like this Black Swallowtail. It is usually possible to pull detail from underexposed shadows. On the other hand, detail is lost when the highlights are “blown out.” What’s the solution? Expose for the shadows and use exposure compensation to capture detail in the highlights.

Related Resource: The exposure triangle and exposure compensation

Copyright © 2017 Walter Sanford. All rights reserved.

Big Bluet damselfly (mating pairs)

September 3, 2017

Hundreds, if not thousands, of Big Bluet damselflies (Enallagma durum) were spotted on 30 August 2017 during a photowalk along Deephole Point Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

A mating pair of Big Bluet was spotted “in heart.” The male is on the upper-right; the female on the lower-left.

30 AUG 2017 | OBNWR | Big Bluet (mating pair, “in heart“)

Big Bluet females are polymorphic, including a blue morph and brown morph. The female in this mating pair is a blue andromorph.

30 AUG 2017 | OBNWR | Big Bluet (mating pair, “in heart“)

I photographed the following male because he was perching at the right height for me to take the shot while standing. I took one photo before he flew to another perch, closer to the ground.

30 AUG 2017 | OBNWR | Big Bluet (male)

As it turns out, the single male led me to another mating pair of Big Bluet that I hadn’t noticed!

30 AUG 2017 | OBNWR | Big Bluet (mating pair, “in heart“)

The female in the preceding mating pair is a brown heteromorph. Color is a highly variable field marker, and describing color is subjective. In my experience, the heteromorph female Big Bluets native to Northern Virginia are light tan to light olive drab in color.

Copyright © 2017 Walter Sanford. All rights reserved.

Before and After

August 24, 2017

On Saturday, 25 January 2014, I had the honor of co-presenting a program called “Flying Dragons” with Kevin Munroe, former Park Manager, Huntley Meadows Park. Kevin invited me to talk about how to make the transition from a beginner- to intermediate/advanced-intermediate dragonfly hunter. I prepared a photoblog post related to my part of the program, called “Five steps to the next level of dragonfly spotting.” Step 1 is as follows.

Step 1. Be aware the same species of dragonfly may appear differently depending upon gender, age, and natural variation. Some species display sexual dimorphism; in contrast, both genders look virtually identical for some species. Finally, females of some species display polymorphism (also known as polychromatism).

Male Needham’s Skimmer dragonflies (Libellula needhami) look different depending upon age, as shown by the “Before” and “After” photos (below). Further, immature male Needham’s Skimmers look similar to immature/mature females of the same species. Although this might be confusing for a beginner dragonfly hunter, with patience and persistence everything falls into place relatively quickly.

Before

Male Needham’s Skimmers were photographed during photowalks at Painted Turtle Pond, Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA in late-June and again in late-July. Notice the dramatic difference in appearance of the same species of dragonfly.

After

Copyright © 2017 Walter Sanford. All rights reserved.


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