Posts Tagged ‘Fairfax County’

Crayfish

May 26, 2017

A crayfish was spotted in the shallows of Bull Run, under several inches of water. I estimate it was 3-4 in (~7.6-10.2 cm) in length.

Many crayfish can be particularly hard to identify from a photograph and many new species are still being discovered in Virginia’s waterways. This large crayfish is from the Family Cambaridae and is likely a native species. Other crayfish found in Northern Virginia, like the rusty crayfish (Orconectes rusticus) and red swamp crayfish (Procambarus clarkii), were likely introduced via the food industry and pose a serious threat to native crayfish populations. Source Credit: John Burke, Ecologist III, Stormwater Management Branch, Fairfax County Department of Public Works and Environmental Services.

10 MAY 2017 | Fairfax County, VA | crayfish (underwater)

Notice the first, second, and third pairs of walking legs feature chelae (plural).

A chela /kˈiːlə/, also named claw, nipper, or pincer, is a pincer-like organ terminating certain limbs of some arthropods. The name comes from Greek (χηλή) through New Latin (chela). The plural form is chelae. Legs bearing a chela are called chelipeds. Source Credit: Chela (organ), Wikipedia.

Also notice the slimy stuff on the rocks that makes them super slippery!

The slimy, slippery coating you find on rocks in aquatic systems is periphyton. In freshwater systems, periphyton is mostly comprised of algae but other microorganisms and detritus also collect on submerged rocks. Periphyton serves as an essential food source to many aquatic organisms and can also act as a bioindicator, signaling changes in water chemistry and nutrient levels in the system (Chetelat et al. 1997). Source Credit: John Burke.

Tech Tip:  My Canon 580EX Speedlite external flash unit was set for 1/16 power in order to penetrate the water and illuminate the subject on a bright, sunny day.

Copyright © 2017 Walter Sanford. All rights reserved.

Eastern Hog-nosed Snake

May 24, 2017

The only downside — or upside, depending upon your point of view — to my new hotspot for hunting odonates is there are only two trails in/out and both paths are steeply-inclined. Going in, not so bad walking downhill; going out, not so much fun!

I stopped to catch my breath as I was walking up a long trail with a 45-degree slope. I heard a rustling sound in the vegetation on the left side of the trail, a little beyond where I was standing. I moved closer slowly until I spotted my first Eastern Hog-nosed Snake (Heterodon platirhinos)!

10 MAY 2017 | Fairfax County, VA | Eastern Hog-nosed Snake

Although the name for this snake is less than flattering, notice the distinctive orange fleur-de-lis shape on top of its head. The coloration of Eastern Hog-nosed Snake is variable; I was fortunate to see one of the more colorful ones.

10 MAY 2017 | Fairfax County, VA | Eastern Hog-nosed Snake

I never had a clear view of the entire snake, but I estimate it was two-to-three feet in length.

Copyright © 2017 Walter Sanford. All rights reserved.

The party’s over

May 22, 2017

Several Eastern Pondhawk dragonflies (Erythemis simplicicollis) were spotted during a photowalk along a mid-size stream in Fairfax County, Virginia USA.

10 MAY 2017 | Fairfax County, VA | Eastern Pondhawk (immature male)

For some types of dragonflies, immature males have the same coloration as females of the same species. This is true for many members of the Family Libellulidae (Skimmers) such as Eastern Pondhawk. Terminal appendages can be used to identify gender.

10 MAY 2017 | Fairfax County, VA | Eastern Pondhawk (female)

The Backstory

I visited a new location in Fairfax County, Virginia on 03 May 2017, following my hunch that the spot might be a good place to find some of the more uncommon species of odonates. Turns out my hunch was right!

I revisited the same location a week later. Let’s just say lightning didn’t strike the same place twice. I saw several Eastern Pondhawks but none of the uncommon species of odonates that I saw a week earlier. I don’t know whether it’s phenology or the fact that Eastern Pondhawks are voracious predators, but it seems like whenever they show up it’s game over for the uncommon species of dragonflies and damselflies that emerge during spring. By the way, that explains the title of this post.

When I see the first-of-season Eastern Pondhawks, I start singing “The Party’s Over” like Don Meredith used to at the end of Monday Night Football games on ABC-TV. Yes, I’m old enough to remember Dandy Don!

Related Resources:

Copyright © 2017 Walter Sanford. All rights reserved.

Ashy Clubtail dragonfly (male)

May 20, 2017

An Ashy Clubtail (Phanogomphus lividus) was spotted during a photowalk along a mid-size stream in Fairfax County, Virginia USA.

03 MAY 2017 | Fairfax County, VA | Ashy Clubtail (male)

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

03 MAY 2017 | Fairfax County, VA | Ashy Clubtail (male)

The last photo is uncropped. The wider view shows the Ashy Clubtail is well-camouflaged when perching on the ground.

03 MAY 2017 | Fairfax County, VA | Ashy Clubtail (male)

The Backstory

I visited a new location in Fairfax County, Virginia on 03 May 2017, following my hunch that the spot might be a good place to find some of the more uncommon species of odonates. Turns out my hunch was right!

I saw species from four families of dragonflies: male Stream Cruiser dragonfly (Didymops transversa); male Springtime Darner dragonfly (Basiaeschna janata); female and male Common Baskettail dragonfly (Epitheca cynosura); female and male Spine-crowned Clubtail dragonfly (Hylogomphus abbreviatus); at least two male Lancet Clubtail dragonflies (Phanogomphus exilis); and the male Ashy Clubtail (Phanogomphus lividus) featured in this post.

In addition, I saw lots of teneral damselflies from the Family Coenagrionidae (Pond Damsels), possibly Blue-tipped Dancer (Argia tibialis).

03 MAY 2017 | Fairfax County, VA | teneral damselfly

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.

Lancet Clubtail dragonflies (males)

May 14, 2017

At least two Lancet Clubtail dragonflies (Phanogomphus exilis) were spotted during a photowalk along a mid-size stream in Fairfax County, Virginia USA.

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

These individuals are males, as indicated by their terminal appendages and indented hind wings.

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

The next photograph was taken at a later time than the first two photos. All of the photos in this post were taken near the same location. Is this another male, or the same one featured in the preceding photos? Who knows?

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

Lancet Clubtail versus Ashy Clubtail

Lancet Clubtail looks similar to Ashy Clubtail (Phanogomphus lividus). The only way to differentiate the two species with certainty is to examine their external reproductive anatomy; this is impossible unless the specimens are captured and examined in-hand.

Relative size is used sometimes to identify the two species: Lancet Clubtail is slightly smaller than Ashy Clubtail. There are two problems with this method of identification. First, it is virtually impossible to determine the exact size of a specimen in the field unless it is captured and measured. Second, some natural variation in size should be expected among individuals of the same species.

A quick-and-dirty method for differentiating Lancet- and Ashy Clubtails with some degree of certainty is to look at the markings on abdominal segments eight and nine (S8-9). Lancet Clubtail has a “spearpoint” on top of abdominal segment eight (S8) that almost reaches the end of the segment, a wide yellow stripe on top of segment nine (S9), and irregular yellow markings on the sides of segments eight and nine (S8-9).

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

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

In contrast, Ashy Clubtail has a spearpoint on top of abdominal segment eight (S8) that is less than half the length of the segment, segment nine (S9) may or may not have a pale yellow stripe on top, and the sides of segments eight and nine (S8-9) may or may not have “poorly defined” yellow markings.

03 MAY 2017 | Fairfax County, VA | Ashy Clubtail (male)

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

Coloration is variable among individuals of the same species, so looking at abdominal markings isn’t always a reliable method of identification. In this case, it works beautifully.

Editor’s Note: The word “spearpoint” and the phrase “poorly defined” are descriptors attributed to Dennis Paulson, Dragonflies and Damselflies of the East (Princeton Field Guides). Princeton University Press. Kindle Edition.

Copyright © 2017 Walter Sanford. All rights reserved.

Green-eyed Stream Cruiser

May 12, 2017

Stream Cruiser dragonfly (Didymops transversa) was spotted during a photowalk along a mid-size stream in Fairfax County, Virginia USA. This individual is a male, as indicated by his terminal appendages and indented hind wings.

03 MAY 2017 | Fairfax County, VA | Stream Cruiser (male)

Male: Eyes brown with green highlight above. … Female: Eyes brown. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 7192, 7194-7195). Princeton University Press. Kindle Edition.

I’ve never seen a green-eyed Stream Cruiser like this one — every one had brown eyes, including both males and females.

Copyright © 2017 Walter Sanford. All rights reserved.

Spine-crowned Clubtail (terminal appendages)

May 10, 2017

A male and female Spine-crowned Clubtail dragonfly (Hylogomphus abbreviatus) 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 Spine-crowned Clubtail is essentially a wide plate with two prongs.

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

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

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). Also notice the right hind wing of the male is slightly malformed.

Female

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

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (female)

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

Copyright © 2017 Walter Sanford. All rights reserved.

Spine-crowned Clubtail dragonfly (male)

May 8, 2017

A Spine-crowned Clubtail dragonfly (Hylogomphus abbreviatus) was spotted recently in Fairfax County, Virginia USA. Spine-crowned Clubtail is relatively uncommon in Northern Virginia, and a new species of dragonfly for my life list.

This individual is a male, as indicated by his terminal appendages and indented hind wings. Notice the right hind wing is slightly malformed.

Spine-crowned Clubtail versus Cobra Clubtail

Spined-crowned Clubtail looks similar to Cobra Clubtail (Gomphurus vastus). Two field markers can be used to differentiate the species.

Spine-crowned Clubtail features large yellow spots on the sides of abdominal segments eight and nine (S8-9); Cobra Clubtail has a small yellow spot on the side of abdominal segment eight (S8) and a large yellow spot on the side of abdominal segment nine (S9), as shown below (see inset photo).

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

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

The face of Spine-crowned Clubtail is yellow and unmarked; the face of Cobra Clubtail is yellow with horizontal black markings (see inset photo).

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

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

More photos, Spine-crowned Clubtail

This guy was a cooperative model as I followed him to several perches on rocks along a large stream.

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

03 MAY 2017 | Fairfax County, VA | Spine-crowned Clubtail (male)

Editor’s Notes: Special thanks to Mike Boatwright, curator of the Virginia Odonata Facebook group, for help in verifying my tentative field identification. As far as I know, this is the first official record for Hylogomphus abbreviatus in Fairfax County, Virginia.

Copyright © 2017 Walter Sanford. All rights reserved.

Springtime Darner dragonfly (male)

May 6, 2017

(✔︎) Springtime Darner dragonfly (Basiaeschna janata).

Well, now that I’ve seen a Springtime Darner, I can stop hunting for the species this year. Huh? I saw one Springtime Darner in 2015 (my first) and another one in 2016, both females. Apparently, Mother Nature allows me to see one and only one Springtime Darner per year. So check-off Springtime Darner from my target list of species for 2017 and move along, nothing more to see here folks. But seriously, hope springs eternal so I’ll keep looking for this somewhat elusive species.

03 MAY 2017 | Fairfax County, VA | Springtime Darner (male)

This Springtime Darner is a handsome male, as indicated by his terminal appendages and indented hind wings. (The former field marker is shown more clearly than the latter.) The blue coloration along its abdomen also indicates this individual is a male, although less reliably than other field markers since female Springtime Darners are polymorphic including blue and green morphs.

Look closely at the full-size version of the preceding photo — there’s some wild stuff going on in his eyes!

The Backstory

During the dragonfly-hunting “off season,” I had a hunch that a new location in Fairfax County, Virginia USA might be a good place to find some of the more uncommon species of odonates. On 03 May 2017, I visited the spot for the first time. I hiked in and began exploring a mid-size stream. After approximately 30-45 minutes of intensive searching, I hadn’t seen any dragonflies or damselflies and was thinking about moving on to another tried-and-true ode-hunting location.

Fortunately, I noticed something out of the corner of my eye that made me stop: a dragonfly that was perching near the ground made a quick, low flight to a new perch. I didn’t see the exact spot where it landed, but I had an idea of the area where it might be. Turns out it was a male Stream Cruiser dragonfly. The male Springtime Darner (featured in this post) was the next dragonfly I spotted soon afterward. Then it’s like the flood gates opened and I saw lots of other odonates including a new species of dragonfly for my life list.

So what’s the take-away from this experience? It’s a cliche, but persistence pays — don’t give up too soon! Oh, and follow your hunches, otherwise you’ll never know whether you are right. Speaking of hunches, I have a good hunch I’ll revisit the new site soon.


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