Archive for the ‘education’ Category

Odonate Calendars (updated for 2020)

July 15, 2020

Phenology (noun) is defined as “the study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life.”

There is an annual cycle of odonate activity that can be subdivided into three broad categories: Early Season (spring); Mid-season (summer); and Late Season (fall).

A calendar is a good way to visualize odonate phenology. I created a new blog page called “Odonate Calendars” (see right sidebar) that features several calendars showing the adult flight period for all species of dragonflies and damselflies that can be found in the Commonwealth of Virginia.

The page includes two interactive calendars for Dr. Steve Roble’s excellent datasets for the Commonwealth of Virginia: one for dragonflies; another for damselflies. Other calendars are provided under “Related Resources.”

Copyright © 2020 Walter Sanford. All rights reserved.

Sable Clubtail dragonfly (male, No. 2)

July 10, 2020

A Sable Clubtail dragonfly (Stenogomphurus rogersi) was spotted by Michael Powell during a photowalk at a location in Fairfax County, Virginia USA. This individual is a male, as indicated by his “indented” hind wings, and terminal appendages.

Look at the blade of grass on which the Sable is perched. Notice the “leftovers” from an afternoon snack eaten by the dragonfly before the photo was taken.

13 JUN 2020 | Fairfax County, VA | Sable Clubtail (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 Sable Clubtail is essentially a wide plate with two prongs.

13 JUN 2020 | Fairfax County, VA | Sable Clubtail (male)

The spiky green grass shown below is probably shallow sedge (Carex lurida) according to Drew Chaney, a.k.a., “Plant Man Drew.”

13 JUN 2020 | Fairfax County, VA | Sable Clubtail (male)

Field Observations

All of the photos in the preceding gallery show male No. 2 perched on vegetation overhanging a small stream, enabling him to both hunt/feed and wait for an opportunity to mate with a female.

Natural History: Males perch on sunlit vegetation overhanging stream or on flat rocks in shade at head of riffle, fly up into trees when disturbed. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 6102-6103). Princeton University Press. Kindle Edition.

In my experience, Sable Clubtails — both male and female — also perch on ground cover vegetation in sunny clearings near small streams. For example, see my recent blog post featuring male No. 1.

Sable does in fact fly up into trees when their “flight” response is triggered by overzealous photographers; they have been observed perched in trees as high as 20 feet above the ground. Be patient — usually they return to the ground soon afterward.

Related Resources

Copyright © 2020 Walter Sanford. All rights reserved.

Sable Clubtail dragonfly (male, No. 1)

June 26, 2020

After a two-year hiatus since I spotted my first Sable Clubtail dragonfly (Stenogomphurus rogersi) during June 2018, it was a pleasure see an old friend again!

The first photo is the “record shot” for this individual, that is, “get a shot, any shot.” It is literally the first shot I took as soon as I spotted the Sable male. As you can see, he was looking in my direction so I was unable to sneak up on him. That proved to be problematic.

13 JUN 2020 | Fairfax County, VA | Sable Clubtail (male)

I tried to move slowly into position for a lateral view of the dragonfly.

13 JUN 2020 | Fairfax County, VA | Sable Clubtail (male)

The last photo is almost as far as I moved before Mr. Sable flew away — five shots and it was game over, man!

13 JUN 2020 | Fairfax County, VA | Sable Clubtail (male)

Later the same day I  was fortunate to photograph a more cooperative male that will be featured in a follow-up post.

Rare to Uncommon

Sable Clubtail has a limited range and is classified as a rare to uncommon species of odonate. The following map shows all official records for Sable Clubtail in the United States of America.

DSA Distribution Viewer | Sable Clubtail

Source Credit: Abbott, J.C. 2006-2018. OdonataCentral: An online resource for the distribution and identification of Odonata. Available at http://www.odonatacentral.org. (Accessed: June 11, 2018).

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

As you would expect, there are few official records for the Commonwealth of Virginia, and fewer records for Northern Virginia.

The Backstory

A short segment of a small stream that flows through a park in Northern Virginia seems to provide ideal habitat for Sable. By the end of Summer 2018, the stream had been degraded significantly by siltation as a result of runoff from dirt that was dumped uphill from the stream.

The following year, the stream channel was almost completely choked by vegetation that I assume flourished in the nutrient-rich sediment that had flowed into the stream. Net result: One and only one Sable Clubtail dragonfly was observed by several spotters who visited the stream site during 2019.

That’s the bad news. The good news is I saw at least three Sable Clubtails when I visited the stream site on Saturday, 13 June 2020. That’s not as many individuals as I saw in 2018, but the species seems to have rebounded a little from the damage done to its habitat.

As Jeff Goldblum said in Jurassic Park, “Life finds a way.” Let’s hope!

Related Resources

Copyright © 2020 Walter Sanford. All rights reserved.

Arrowhead Spiketail dragonfly (male)

June 17, 2020

An Arrowhead Spiketail dragonfly (Cordulegaster obliqua) was spotted during a recent photowalk with Michael Powell at a location in Fairfax County, Virginia USA.

08 JUN 2020 | Fairfax County, VA | Arrowhead Spiketail (male)

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

08 JUN 2020 | Fairfax County, VA | Arrowhead Spiketail (male)

The Backstory

At the end of a long day in the field, Mike Powell and I were walking back to the car slowly when we spotted a group of 10-or-so large dragonflies hawking insects over a HUGE field, near a small drainage pipe. We stopped to watch the hawkers hoping one would land; I sat on my Coleman camp stool to rest in the shade and enjoy the aerial acrobatics show.

One of the large dragonflies zoomed past Mike (he says he never saw it) and landed on a tall grass stem near the drainage pipe. It was the male Arrowhead Spiketail shown above!

Turns out the place is nothing like the habitat described as ideal (see below). I’ll say this: Three out of four times I’ve seen Arrowhead Spiketails, a fly-by was how I found them. So maybe just sit in a good spot and wait for the game to come to you. Maybe.

Habitat

Disclaimer: I have observed and photographed four (4) Arrowhead Spiketail dragonflies. I feel somewhat uncomfortable providing habitat guidance based upon a sample size of four. That being said, here goes.

Almost every Arrowhead siting had three common ingredients: a seep (or soggy place) in the forest, with skunk cabbage (Symplocarpus foetidus) and interrupted fern (Osmunda claytoniana); a small stream in the forest fed by the seep/soggy place; and a sunny clearing.

I found my first Arrowhead Spiketail at a small stream in Huntley Meadows Park. I walked the stream to its source, not that the source is well defined. Instead it’s a BIG soggy area. I wouldn’t call it a seep and I have never seen skunk cabbage anywhere in the park. There are two virtually identical streams elsewhere in the park where Arrowhead has been photographed. The male Arrowhead flew a LONG patrol along the stream, flying approximately six inches (6″) above the water level. At the end points of his patrol, he would hang up to rest in a sunny spot. It took a long time for me to find the hang up places!

Michael Powell spotted the second Arrowhead Spiketail I’ve seen, perched in a small, sunny clearing in the forest along a small stream. A seep with skunk cabbage and interrupted fern was located nearby. For what it’s worth, we saw/photographed several Gray Petaltail dragonflies (Tachopteryx thoreyi) in the same field.

MUCH FARTHER downstream, the same creek is a little larger in size. At one point, a small iron-stained creek flows into the main creek. Mike and I were standing at the mouth of the tiny creek when I saw an Arrowhead fly like a bat out of hell straight down the stream and turn left; it perched in a large, sunny field. I was able to find it, and we took photos. A week-or-so later, Mike traced the smaller creek to its source. Wouldn’t you know it? The headwaters are a seep with lots of skunk cabbage!

My most recent Arrowhead Spiketail sighting — the individual featured in this blog post — is the one that doesn’t fit the pattern. The dragonfly was spotted in a HUGE field of grasses, etc. There are small creeks and seeps nearby, but not within sight of the location where the Arrowhead perched.

Related Resources

Copyright © 2020 Walter Sanford. All rights reserved.

Cobra Clubtail dragonflies (females)

June 12, 2020

At least 11 Cobra Clubtail dragonflies (Gomphurus vastus) were spotted during a photowalk with Michael Powell in Fairfax County, Virginia USA, including 10 females and one male. This blog post features photos of the first two females that I spotted.

No. 1a

08 JUN 2020 | Fairfax County, VA | Cobra Clubtail (female)

This individual is a female, as indicated by her terminal appendages and rounded hind wings. Notice the injury to her right rear leg.

08 JUN 2020 | Fairfax County, VA | Cobra Clubtail (female)

No. 1b

Inspired by Fred Siskind’s portfolio of dew-covered insects, Mike Powell and I are on a never-ending quest to find and photograph dew-covered odonates. The last photo shows my best effort to date.

As we were photographing female No. 1a, I noticed another individual perched nearby. No. 1a was perched in a sunny spot where most of the morning dew had evaporated; No. 1b was perched in a shady spot where everything was still covered by dew.

08 JUN 2020 | Fairfax County, VA | Cobra Clubtail (female)

Unfortunately, this female was quite skittish so her glamor shoot was one-and-done.

What is dew and how does it form?

Dew forms when the atmosphere is cooled until its temperature reaches the “dew point temperature” and water vapor in the atmosphere (an invisible gas) condenses to become liquid water. (The temperature when this phase change occurs is also known as the “frost point temperature.”)

The dew point temperature varies depending upon the amount of moisture in the air. Typical dew points in the mid-Atlantic states are in the 60s and 70s during the summer months, 40s and 50s during spring and fall, and 20s and 30s during winter.

Check your local weather forecast to see whether the predicted overnight low air temperature will reach the dew point temperature. Sometimes close is good enough, as surfaces that are good radiators of thermal energy can cool a thin layer of air to the dew point.

Related Resources

Copyright © 2020 Walter Sanford. All rights reserved.

Common Green Darner dragonfly (external female reproductive anatomy)

June 5, 2020

For some species of odonate exuviae, sex is indicated by a form of remnant reproductive anatomy. These external structures don’t look exactly the same for all species of dragonflies and damselflies, but their function is identical.

As far as I know, this is true for all species in the Family Aeshnidae (Darners) such as Common Green Darner dragonfly (Anax junius).

The following photograph shows a ventral view of a female Common Green Darner dragonfly. Notice the external reproductive anatomical structure on abdominal segment nine (S9) is virtually identical to the remnant anatomical structure on S9 of the exuvia, shown above.

Original photo used with permission from Louisa C. Craven.

The Backstory

My dear friend Louisa Craven discovered the lifeless adult dragonfly while on vacation with her family in Nags Head, North Carolina USA. Louisa is an accomplished wildlife photographer who developed an interest in odonates as a result of many photowalks with me.

Related Resources

Copyright © 2020 Walter Sanford. All rights reserved.

Splendid Clubtail dragonfly (female)

June 3, 2020

A Splendid Clubtail dragonfly (Gomphurus lineatifrons) was spotted during a photowalk with Michael Powell at an undisclosed location in Fairfax County, Virginia USA. Easy for me to say now. As it turns out, my initial identification was incorrect.

The first photo I took of the dragonfly — the record shot — is shown below. Notice the pattern of yellow lateral marks/spots on its abdomen. Also notice the yellow blotch on the side of abdominal segment eight (S8) extends onto the club flange, as shown in the full-size version of the image. (Thanks to Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, for sharing these key field marks for Splendid.)

26 MAY 2020 | Fairfax County, VA | Splendid Clubtail (female)

In contrast, the pattern of yellow lateral marks/spots on the abdomen of a female Cobra Clubtail (Gomphurus vastus), shown below, looks quite different. And the yellow blotch on S8 DOES NOT EXTEND onto the club flange, as shown in the full-size version of the image.

09 MAY 2017 | Riverbend Park | Cobra Clubtail (female)

The last photo, published in a recent blog post, is the one that caused me to misidentify the dragonfly. Notice the pattern of yellow mid-dorsal lines/marks is somewhat similar for both Cobra Clubtail (above) and Splendid Clubtail (below).

26 MAY 2020 | Fairfax County, VA | Splendid Clubtail (female)

This individual is a female, as indicated by her terminal appendages and rounded hind wings.

The Backstory

My last blog post features an actual female Cobra Clubtail dragonfly that I spotted soon after seeing the Splendid Clubtail shown above.

The Cobra appeared to be noticeably smaller than the Splendid, and in fact it is. Cobra is 4.7-5.7 cm in total length; Splendid is 6.7-6.9 cm. In my experience it’s often difficult to judge the relative size of dragonflies in the field. That being said, a difference of ~2.0 cm in length was easy to see.

There is, of course, some natural variation in size among individuals of the same species. I walked around the rest of the day wondering why the two “Cobra” that I’d seen were so different in size. The answer seems obvious in retrospect: the larger one is Splendid; the smaller one is Cobra.

Official Records

When my friend Mike Powell submitted an official record for the Splendid Clubtail, he followed my lead and called it Cobra Clubtail. Mike included a photograph showing a dorsal view of the dragonfly that looks similar to my dorsal view.

Rick Cheicante and Mike Boatwright, two vetters for the Odonata Central records database, thought the dragonfly might be Splendid rather than Cobra. Mike Boatwright contacted me and asked to see more photos of the Splendid. One look at my photo showing a side view of the individual and Mike B. knew immediately the “Cobra” is actually Splendid.

So what’s the take-away? It’s good to be wrong, in fact, it’s Splendid! (See what I did there?) Especially when Splendid Clubtail is a new species for my life list as well as a new species for Fairfax County, Virginia USA.

And while I’m giving credit where credit is due, it should be noted that Kevin Munroe, former manager of Huntley Meadows Park, deserves credit as the first person to discover Splendid Clubtail in Fairfax County, Virginia USA. Although Kevin didn’t submit official records for his finds, he beat me to the discovery by nearly a decade!

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 Gomphurus lineatifrons is from May 01 to June 27. The species is classified as uncommon. Its habitat is “rivers.”

Bear in mind, Dr. Roble’s records are for the entire state, therefore the adult flight period for Gomphurus lineatifrons seems to be longer than it is in reality. The adult flight period for a single site is probably shorter. For example, according to records for Northern Virginia maintained by Kevin Munroe, former manager of Huntley Meadows Park, the adult flight period for Splendid Clubtail is May 28 to June 15.

Related Resource: Gomphurus lineatifrons (Splendid Clubtail)

Copyright © 2020 Walter Sanford. All rights reserved.

Cobra, Cobra! / Splendid Clubtail

May 27, 2020

POST UPDATE

It’s good to be wrong! Huh? Upon further review, this individual is a Splendid Clubtail dragonfly (Gomphus lineatifrons). Easy mistake to make since I had never seen Splendid — a new species for my life list as well as a new species for Fairfax County, Virginia USA. Sincere thanks to Rick Cheicante and Mike Boatwright for setting the record straight! More later in a follow-up blog post.


A Cobra Clubtail dragonfly (Gomphurus vastus) was spotted during a photowalk with Michael Powell at an undisclosed location in Fairfax County, Virginia USA.

26 MAY 2020 | Fairfax County, VA | Cobra Clubtail (female)

This individual is a female, as indicated by her terminal appendages and rounded hind wings.

Related Resources

Copyright © 2020 Walter Sanford. All rights reserved.

Macromia illinoiensis exuvia (face-head)

May 20, 2020

The following photograph of a Swift River Cruiser dragonfly (Macromia illinoiensis) exuvia shows a prominent horn on the face that is a key field mark for larvae/exuviae in the Family Macromiidae (Cruisers).

The specimen was collected, with permission from park staff, on 27 May 2017 along the Potomac River at Riverbend Park in Fairfax County, Virginia USA.

Tech Tips

The subject was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique. The specimen was posed on its dorsal side, so the camera was focused on the face-head-ventral view of the exuvia. The final image was cropped and rotated 180° during post-processing.

10 photos of the specimen were taken using an aperture of f/16; in-camera focus peaking was used to highlight select areas in each photo. RAW FILE CONVERTER EX 3.0 was used to convert Fujifilm RAF files to TIFF files. Adobe Photoshop CC 2017 was used to create a focus-stacked composite image that was edited using Apple Aperture.

Editor’s Note: This blog post is the last installment in what turned out to be a three-part series. The featured focus-stacked composite image is a little closer to what I had in mind when I set up the photo shoot.

  1. MYN – Macromiidae larvae/exuviae are horny
  2. RAW FILE CONVERTER EX 3.0

Copyright © 2020 Walter Sanford. All rights reserved.

RAW FILE CONVERTER EX 3.0

May 18, 2020

RAW FILE CONVERTER EX 3.0 powered by SILKYPIX is a free application available for download from Fujifilm USA. The application can be used to convert Fujifilm RAF files to TIFF files.

The application is somewhat counterintuitive. For example, if you look at the File menu (shown in the menubar) notice “Export” isn’t an option.

Instead, images are exported from the Development menu.

First, select “Development / File output settings…” and configure the menu settings as shown below (or as appropriate for your purposes).

If you’d like to export several files, then select “Development / Batch development settings…” and configure the menu settings as shown below (or as appropriate for your purposes).

Use the left sidebar to navigate to a set of RAF files, then choose the images that you’d like to convert to TIFFs. Select “Development / Batch develop selected images…” [It’s worth noting that after selecting one or more images, some of the items in the “File” menu are no longer grayed-out. Selecting “File / Batch develop selected images…” is the same as working from the “Development” menu.]

Next a pop-up window appears; click the button labeled “Batch develop.”

The following window shows the progress of the file conversion process.

Tech Tips

“RAW FILE CONVERTER EX 3.0″ can be used to edit photos too. I have no interest in learning to use a new application for editing photos — I know how to use “Apple Aperture” and “Adobe Lightroom” already. The free application from Fujifilm is simply a utility that enables me to convert RAF files that I can’t open and edit on my older Apple iMac desktop computer to TIFFs that I can open/edit.

That being said, the application appears to be fairly robust and has some features that might be worth exploring.

The step-by-step instructions provided in this guide were discovered by limited experimentation. If you know a better/simpler way to accomplish the same task, then please comment on this post. Thank you!

Related Resource: MYN – Macromiidae larvae/exuviae are horny, a blog post by Walter Sanford (see section entitled “Tech Tips”).

Copyright © 2020 Walter Sanford. All rights reserved.


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