Posts Tagged ‘male’

Urban Heat Island

December 10, 2017

On 01 December 2017 I didn’t see any Autumn Meadowhawk dragonflies (Sympetrum vicinum) during a photowalk along Easy Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

In contrast, I saw several Autumn Meadowhawks perched on man-made structures such as a concrete curb in the blacktop parking lot at the refuge. All of the dragonflies were perched on vertical surfaces that received more direct insolation than horizontal surfaces. The parking area seems to be an urban heat island microclimate that exists within a larger natural area.

Male 1

The first individual is a male, as indicated by his terminal appendages. Although the male is missing one of four wings, he was able to fly well enough to move to three different perches along the curb.

01 DEC 2017 | Occoquan Bay NWR | Autumn Meadowhawk (male, injured)

01 DEC 2017 | Occoquan Bay NWR | Autumn Meadowhawk (male, injured)

01 DEC 2017 | Occoquan Bay NWR | Autumn Meadowhawk (male, injured)

Male 2

The next male has a full set of four wings; his wings are tattered slightly, as expected toward the end of dragonfly season.

The last photo shows the male grooming and excreting at the same time.

Related Resources

Copyright © 2017 Walter Sanford. All rights reserved.

Advertisements

“Winter Meadowhawk” dragonflies

December 8, 2017

The season called “winter” is defined two ways: atmospheric scientists, including meteorologists and climatologists, define winter as the three-month period from December to February; astronomers define winter as the time period that begins on the December Solstice (12/21) and ends on the March Equinox (03/21), although the actual dates for these events may vary slightly.

Several Autumn Meadowhawk dragonflies (Sympetrum vicinum) were spotted on the first day of climatological winter at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. Therefore I think it is appropriate to call them “Winter Meadowhawks.”

The last two photos show the same male, perching on different surfaces. My guess is he was looking for a good source of thermal energy on a cool, windy day.

The Sun is always low in the sky during winter, even at its maximum altitude. Indirect incoming solar radiation (insolation) is less intense than direct insolation. The last photo shows the male dragonfly perched on a south-facing wooden board that is perpendicular to the surface of the Earth, therefore the solar energy received by the board is more intense than the energy received by the ground. This probably explains why the male moved from the ground to the board.

Enrichment

The last photo was taken on 01 December 2017 at 11:33:50 a.m. EST, as shown by the EXIF information for the image. The altitude of the Sun was 28.9° at 11:30 a.m., meaning a ray of sunlight formed an angle of 28.9° with horizontal surfaces such as the ground. At the same time, a ray of sunlight formed an angle of 61.1° with vertical surfaces such as the wooden board shown in the first and last photos. That’s the beauty of mathematics — some simple geometry shows clearly which surface received more intense insolation. Smart dragonflies!

Related Resource: Sun or Moon Altitude/Azimuth Table, U.S. Naval Observatory.

Copyright © 2017 Walter Sanford. All rights reserved.

Incredible!

December 4, 2017

Odonates are aquatic insects. They spend most of their life as larvae that live in water; this stage of their life cycle can last from a few months to a few years. Finally, they emerge from the water and metamorphose into adults in order to reproduce; their offspring return to the water and the cycle begins again.

Careful and/or lucky observers will notice exuviae (sing. exuvia), also known as either “cast skins” or “shed skins,” left behind when odonate larvae emerge. Would you believe this…

metamorphosed into that? (See below.) It’s a miraculous transformation! The adult stage of the odonate life cycle can last from a week-or-so to a month-or-so, depending upon the species.

The first photo shows an exuvia from a Cobra Clubtail dragonfly (Gomphurus vastus), photographed in situ at Riverbend Park, Fairfax County, Virginia USA. All other photos in this gallery show adult male Cobra Clubtails, as indicated by their terminal appendages and “indented” hind wings.

Copyright © 2017 Walter Sanford. All rights reserved.

A week later…

November 26, 2017

On 09 November 2017 I visited Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA, looking for late-season odonates before the first hard freeze. Several Autumn Meadowhawk dragonflies (Sympetrum vicinum) were spotted during a photowalk along Easy Road.

I revisited the same place one week later. I saw slightly fewer Autumn Meadowhawks than the week before. Although some dragonflies survived the freezing temperatures, their numbers seemed to be diminished according to my non-scientific survey.

Both individuals featured in this photo set are male, as indicated by their terminal appendages.

I love the palette of fall colors in the first two photos! The two-photo sequence shows how I typically “work a shot.” I start by “getting a shot, any shot” (above) and slowly refine the shot until I am able to get as close as the subject will allow, while looking at the overall composition (below). Remember to check the edges of the photo for leading lines and distracting elements.

The last dragonfly I photographed was perched on the wooden border of a flower bed located near the parking lot.

Related Resources: Five Guys; Thermal energy vampire!

Copyright © 2017 Walter Sanford. All rights reserved.

Thermal energy vampire!

November 24, 2017

The following photographs show an Autumn Meadowhawk dragonfly (Sympetrum vicinum) perching on Walter Sanford (hey, that’s me!) at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. This individual is a male, as indicated by his terminal appendages.

All three photos were taken by Lisa Young during a photowalk with me along Easy Road.

Most dragonflies are skittish. Some species of dragonflies are “friendly,” such as Blue Corporal dragonflies (Ladona deplanata) and Autumn Meadowhawk dragonflies (Sympetrum vicinum). It’s probably not a coincidence that both types of dragonflies are early- and late-season species, when the ambient air temperature is cooler.

Some odonate experts speculate dragonflies perch on people in order to absorb thermal energy radiated by the relatively warm human body. Or in this case, a black backpack — a good spot since darker-colored objects absorb and re-radiate thermal energy more quickly than lighter-colored objects.

Related Resource: Five Guys, a blog post by Walter Sanford featuring photos of male Autumn Meadowhawk dragonflies taken before the meet-up with Liza Young.

Copyright © 2017 Walter Sanford. All rights reserved.

Five Guys

November 16, 2017

Several Autumn Meadowhawk dragonflies (Sympetrum vicinum) were spotted along Easy Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. All of these individuals are male, as indicated by their terminal appendages.

Did you notice the preceding male appears to be missing his right hind wing? Perhaps I should rename this blog post “4.75 Guys.”

Editor’s Note: The photos in this gallery were taken a day before the first hard freeze in Northern Virginia that occurred overnight on Friday-Saturday, November 10-11. It will be interesting to see how many Autumn Meadowhawk dragonflies survived the record-setting low temperatures in the mid- to upper 20s.

Copyright © 2017 Walter Sanford. All rights reserved.

Unambiguously Sympetrum ambiguum

November 10, 2017

Two Blue-faced Meadowhawk dragonflies (Sympetrum ambiguum) were spotted during a photowalk along Charlie Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. Although Blue-faced Meadowhawk is on the species list of dragonflies and damselflies at Occoquan Bay NWR, this is the first time I have seen Sympetrum ambiguum at the refuge.

Male

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

19 OCT 2017 | OBNWR | Blue-faced Meadowhawk (male)

This guy was skittish. I was able to take one photo before he flew toward the tree canopy. The preceding photograph is what my good friend Mike Boatwright calls a “record shot,” that is, a photograph that records (verifies) my sighting of the male Sympetrum ambiguum. The photo was cropped slightly for improved composition.

Female

The last individual is a female heteromorph, as indicated by her tan coloration and terminal appendages.

The preceding photograph is my “record shot” of the female. I worked the shot…

…until I found the best viewpoint, shown below.

The first and last photos of the female were cropped slightly for improved composition; the second photo is uncropped.

Copyright © 2017 Walter Sanford. All rights reserved.

Lumix loves him some head-tilts!

November 6, 2017

An Autumn Meadowhawk dragonfly (Sympetrum vicinum) was spotted at Hidden Pond, Meadowood Recreation Area, Fairfax County, Virginia USA. This individual is a male, as indicated by his terminal appendages.

Regular readers of my photoblog know I’m fond of head-tilts in which the dragonfly seems to display some of its personality, especially when the individual is looking at me (below).

OK, so no head-tilt in the last photo, but I like the knot in the wooden dock on which the dragonfly is perching.

Tech Tips

The photographs in this gallery were taken using my Panasonic Lumix DMC-FZ150 superzoom digital camera set for ~24x zoom (focal length of 600mm, 35mm equivalent), and Canon 580EX Speedlite external flash (manual mode).

In order to reduce “camera shake,” the camera was set for shutter priority mode. Using the reciprocal rule, the shutter speed was set for 1/800s. The ISO was set for “100.” An inexpensive Sunpak 6700M aluminum monopod was used for added stability.

Copyright © 2017 Walter Sanford. All rights reserved.

Adding an 11mm extension tube

November 2, 2017

Optics theory

The net effect of adding an extension tube between a lens and camera body is the “working distance” is decreased, that is, the distance from the front of the lens barrel to the subject is decreased. A smaller working distance means the same lens will focus closer to the subject, thereby increasing magnification.

The effect is greater at shorter focal lengths, as shown by the following annotated table of magnification for the two extension tubes sold by Fujifilm USA.

Table courtesy Fujifilm USA.

Theory into practice

On 27 October 2017 several Autumn Meadowhawk dragonflies (Sympetrum vicinum) were spotted perching on the small dock at Hidden Pond, Meadowood Recreation Area, Fairfax County, Virginia USA. All individuals featured in this photo gallery are male, as indicated by their terminal appendages.

All photos in this set were taken using my Fujifilm X-T1 digital camera, Fujinon XF55-200mm zoom lens, and a Fujifilm MCEX-11 extension tube. The camera was set for manual focus in order to use focus peaking; back-button focusing was used to focus automatically.

At 200mm, the working distance of the lens is 905 mm (90.5 cm, ~35.63 in), or approximately three (3) feet. With an 11mm extension tube mounted between the lens and camera body, the working distance is reduced to 665 mm (66.5 cm, ~26.2 in), or a little more than two (2) feet. At a focal length of 55mm, adding the extension tube would result in photos that look more like “macro” photos; at 200mm, adding the extension tube resulted in photos that look like a lens with a longer focal length was used to take the shots.

All of the following photos were slightly cropped for improved composition. The 11mm extension tube is the difference-maker that enables me to take close-up shots using a mid-range telephoto zoom lens such as the Fujinon 55-200mm.

ISO 640 | 200mm (~300mm, 35mm equivalent) | f/11 | 1/500s | -1 ev

ISO 640 | 200mm (~300mm, 35mm equivalent) | f/11 | 1/500s | -1 ev

When I changed the aperture from f/11 to f/16 (larger to smaller opening) for more depth-of-field, notice the ISO increased from 640 to 800. ISO was set for “Auto” with a limit of 800.

ISO 800 | 200mm (~300mm, 35mm equivalent) | f/16 | 1/500s | 0 ev

ISO 800 | 200mm (~300mm, 35mm equivalent) | f/16 | 1/500s | 0 ev

ISO 800 | 200mm (~300mm, 35mm equivalent) | f/16 | 1/500s | 0 ev

ISO 800 | 200mm (~300mm, 35mm equivalent) | f/16 | 1/500s | 0 ev

More tech tips

Focus peaking can be activated when the camera is set for manual mode. Using back-button focus (AF-L button) in manual mode enables one to retain full control of the exposure triangle, focus quickly, and see what’s in focus before shooting a photograph. Fuji Back Button Focus (4:06), a YouTube video by Ashraf Jandali, provides a clear demonstration of how to use back-button focus on the Fujifilm X-T1.

In order to reduce “camera shake,” I almost always shoot in shutter priority mode using the reciprocal rule. Remember, it’s the 35mm equivalent that matters: since my lens is ~300mm, the shutter speed should be set for at least 1/300s; in this case, it was set for 1/500s. In manual mode, I set the shutter speed and aperture; ISO was set for “Auto” with a limit of 800. An inexpensive Sunpak 6700M aluminum monopod was used for added stability.

Editor’s notes

Did you notice I didn’t use an external flash unit to shoot the preceding photos? The afternoon Sun is lower in the sky in late-October than it would be at the same time during mid-summer. I wanted to faithfully capture the shadows cast by the dragonflies in order to convey the feeling that the Sun is setting on these dragonflies, literally for the day as well as figuratively for the current odonate season.

Copyright © 2017 Walter Sanford. All rights reserved.

Quick and dirty macro photos (Part 1)

October 27, 2017

Several Autumn Meadowhawk dragonflies (Sympetrum vicinum) were spotted on 25 October 2017 during a photowalk along the boardwalk in the central wetland area at Huntley Meadows Park, Fairfax County, Virginia USA. All of these individuals are male.

The photographs in this gallery were taken using my Panasonic Lumix DMC-FZ150 superzoom digital camera set for ~12x zoom, Raynox DCR-250 close-up filter, and Canon 580EX Speedlite external flash (manual mode). I estimate the “working distance” between the camera and subject was approximately three-to-six inches (~3-6″). Now that’s what I call cooperative models!

ISO 100 | 56mm (~300mm, 35mm equivalent) | f/4.1 | 1/800s | -1 ev

The following photo is my favorite in the set.

ISO 100 | 56mm (~300mm, 35mm equivalent) | f/4.1 | 1/800s | -1 ev

Each compound eye has approximately 30,000 ommatidia!

ISO 100 | 56mm (~300mm, 35mm equivalent) | f/4.1 | 1/800s | -1 ev

The Raynox DCR-250 close-up filter is a relatively inexpensive solution that enables my Panasonic superzoom digital camera to be used for macro photography. Set-up is quick and easy — the filter simply screws onto the front of the camera lens using a 52-43mm step-down ring.

As you can see, depth-of-field is very shallow, caused in part by shooting in Shutter Priority mode rather than Aperture Priority. A cooperative subject, good light, and a lot of patience are essential for success.

Related Resource: Quick and dirty macro photos (Part 2), a blog post by Walter Sanford featuring photos of a mating pair of Autumn Meadowhawk dragonflies (in wheel).

Copyright © 2017 Walter Sanford. All rights reserved.


%d bloggers like this: