Macromiidae – It’s all about the “horn.”

A “horn” on the face-head is a characteristic field mark for odonate larvae/exuviae in the Family Macromiidae (Cruisers).

Look closely at the full-size version of each of the following photos and you should be able to see the horn on the face of a Stream Cruiser dragonfly (Didymops transversa) exuvia that was collected during mid-April 2021.

13 APR 2021 | PNC. William County, VA | Stream Cruiser exuvia (face-head)

It’s easier to see the horn in the next photo…

13 APR 2021 | PNC. William County, VA | Stream Cruiser exuvia (dorsal)

The horn is clearly visible in the last photo. Notice there are three “bumps” located between the eyes of the exuvia: the middle bump is the horn; the antennae bases are located to the left and right of the horn.

13 APR 2021 | PNC. William County, VA | Stream Cruiser exuvia (dorsal)

Related Resources

• Test shots: Didymops transversa exuvia
• Exuvia from Family Macromiidae (Cruisers)

Copyright © 2021 Walter Sanford. All rights reserved.

Test shots: Didymops transversa exuvia

An exuvia from a Stream Cruiser dragonfly (Didymops transversa) was collected from one of the concrete abutments of a man-made dam located along a mid-size stream at an undisclosed location in Prince William County, Virginia USA.

I prefer to photograph odonate exuvia like this one “as is” — presumably its appearance is similar to the way larva looked when it lived underwater.

13 APR 2021 | PNC. William County, VA | Stream Cruiser exuvia (dorsal)

If so, then I’m guessing D. transversa larvae like to burrow in sediment, as indicated by the dirty dorsal side and relatively clean ventral side of this specimen.

13 APR 2021 | PNC. William County, VA | Stream Cruiser exuvia (ventral)

Post Update

The nymphs are sprawlers that cling to roots or hunker down in sediments of mixed sand and silt particles. Source Credit: K. J. Tennessen, Dragonfly Nymphs of North America, https://doi.org/10.1007/978-3-319-97776-8_10, Macromiidae, p. 330.

The Backstory

The preceding photos were shot using the prototype for a homemade curved clear plastic tray intended for staging subjects against a white background.

With a few minor tweaks, the curved stage performed better than during initial testing. I needed to add a second external flash unit to more evenly illuminate the white background.

Although I’m fairly satisfied with the results of these test shots, more testing is required to be sure the set-up is working the way I want.

Related Resources

• Macromiidae – It’s all about the “horn.”
• Exuvia from Family Macromiidae (Cruisers), a blog post by Walter Sanford featuring in situ photographs of the same specimen.

Copyright © 2021 Walter Sanford. All rights reserved.

Test shots

I have been working on the prototype for a homemade curved clear plastic tray that is intended for staging subjects against a white background.

My goal for Thursday: Test the prototype stage using a toy mini-lizard as the model for some test shots, and if the proof-of-concept were established, substitute an odonate exuvia for the toy lizard and shoot another set of photos.

16 SEP 2021 | BoG Photo Studio | toy mini-lizard

Well, you know what they say about the best laid plans! First, a line of fairly strong thunderstorms moved through the region where I live so I had to shut down my computer equipment. Second, the Washington Football Team played the New York Giants on Thursday Night Football so I had to watch the game. That’s right, had to watch. Turns out it was time well-spent.

Bottom line: I never finished the test shots of the toy lizard, and of course that means I didn’t shoot any photos of a real scientific specimen.

The curved surface of the clear plastic stage caused reflections from the single external flash that was used to light the subject. I had just figured out a work-around when the thunderstorms rolled in: I took 14 test shots; only the last one (shown above) is usable. I hadn’t intended to create a photo with a pure white background, but it was easy to adjust the image exposure during post-processing.

The Backstory

What’s my motivation? Many macro photographers use insect pins for mounting small subjects like odonate exuviae. I think there’s a big problem with that technique: The position of the pin is permanent. In other words, if the pin is attached to the ventral side of the specimen then it’s challenging at best and impossible at worst to take clean, clear shots of that side of the subject. I don’t want to use insect pins because some of my specimens are one of a kind.

For quite some time, I’ve been experimenting with the use of flat clear plastic stages as a solution for this problem. I think a curved stage might be a breakthrough, but more testing is required to be sure.

For example, notice the color fringing near the tip of the lizard’s tail — I’m not sure what caused that problem in only one part of the photo, therefore I don’t know how to fix it. Yet.

To be continued. Please stay tuned.

Copyright © 2021 Walter Sanford. All rights reserved.

Anax junius versus Anax longipes

The following photograph shows the relative size of odonate exuviae from two species in the Genus Anax: junius; and longipes. Both specimens are from the Family Aeshnidae (Darners).

Relative size of exuviae from Anax junius versus Anax longipes.

The Common Green Darner dragonfly (Anax junius) exuvia was collected on 17 June 2021 from a small pond at an undisclosed location in Prince William County, Virginia USA.

The Comet Darner dragonfly (Anax longipes) exuvia was collected by Stanley Caveney on 19 July 2021 from a pond at MeadowWoods in West Elgin, Ontario, Canada.

Taxonomy

There are five species of dragonflies in the Genus Anax for the United States and Canada: Amazon Darner (Anax amazili); Common Green Darner (Anax junius); Comet Darner (Anax longipes); Giant Darner (Anax walsinghami); and Blue-spotted Comet (Anax concolor).

Common Green Darner and Comet Darner are the only species from the Genus Anax found where I live in Northern Virginia USA.

Related Resources

• Post update: What is it? [Anax junius exuvia]
• Comet Darner dragonfly (exuvia) [Anax longipes]

Copyright © 2021 Walter Sanford. All rights reserved.

Comet Darner dragonfly (exuvia)

An odonate exuvia from a Comet Darner dragonfly (Anax longipes) was collected by Stanley Caveney on 19 July 2021 at MeadowWoods in West Elgin, Ontario, Canada.

This specimen is from Family Aeshnidae (Darners), as indicated by the following field marks: the exuvia has a flat labium that doesn’t cover the face (not mask-like); the antennae are thin and thread-like (not club-like, as in Gomphidae larvae/exuviae); and the eyes are large relative to the size of the head.

19 JUL 2021 | Ontario, Canada | Comet Darner exuvia (lateral view)

Lateral spines along abdominal segments seven, eight, and nine (S7-9) indicate the genus is Anax; the length of the exuvia indicates longipes (~6 cm, measured as is).

The Backstory

Stanley Caveney is shown in the first of several photos taken by Hugh Casbourn. Stan contacted me for confirmation of his tentative identification of several Comet Darner exuviae that he collected during July 2021. Stan kindly gave one of the exuviae to me.

Photo used with written permission from Hugh Casbourn.

I asked Stan whether he had taken photographs of the Comet Darner exuviae in situ. Stan hadn’t, so he and Hugh revisited a local pond where they searched for and found two more exuviae.

How many exuviae do you see in the next photo? Look closely — both cast skins are shown in the same image.

Photo used with written permission from Hugh Casbourn.

An exuvia from a female Comet Darner appears in the foreground of the preceding photograph…

Photo used with written permission from Hugh Casbourn.

and a male Comet Darner appears in the background.

Photo used with written permission from Hugh Casbourn.

I asked Stan for advice regarding where to look for Comet Darner exuviae.

The six exuviae found to date were mainly at the inner edge of the cattail beds, facing the open water of the pond and where the individual cattail plants were spaced out. Source Credit: Personal communication from Stanley Caveney.

Related Resource: Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz. Refer to pp. 21-22.

Editor’s Note: Sincere thanks to Derek Caveney, Stan’s son, for shipping the exuvia to me. The specimen was packed so carefully that it arrived in excellent condition, as you can see in the first photo in this blog post. I’m looking forward to shooting a complete photo set of the exuvia.

Copyright © 2021 Walter Sanford. All rights reserved.

Post update: What is it?

I spotted an odonate exuvia along the shoreline of a small pond at an undisclosed location in Prince William County, Virginia USA that was collected by Mike Powell, my good friend and photowalking buddy.

This specimen is from the Family Aeshnidae (Darners), as indicated by the following field marks: the exuvia has a flat labium that doesn’t cover the face (not mask-like); the antennae are thin and thread-like (not club-like, as in Gomphidae larvae/exuviae); and the eyes are large relative to the size of the head.

17 JUN 2021 | PNC. Wm. County | Anax junius exuvia

Lateral spines along abdominal segments seven, eight, and nine (S7-9) indicate the genus is Anax; the length of the exuvia indicates junius (greater than ~4 cm, measured as is).

Common Green Darner dragonfly (Anax junius) is one of the more common species of Aeshnidae found in Northern Virginia.

Related Resource: What is it?

Copyright © 2021 Walter Sanford. All rights reserved.

Uhler’s Sundragon dragonfly exuvia

Michael Powell spotted a small odonate exuvia clinging to the base of one of two concrete abutments for a man-made dam located along a mid-size stream at an undisclosed location in Prince William County, Virginia USA.

I collected the exuvia in order to examine it more closely in my home laboratory/photography studio. Michael photographed the specimen in my hand immediately after I removed it from the abutment, as shown in the following photo.

Photo used with written permission from Michael Powell.

The first photo shows a face-head view of the exuvia.

13 APR 2021 | Prince William County, VA | Uhler’s Sundragon (exuvia)

The next two photos, showing a dorsal-lateral view of the specimen, confirm the exuvia is from a Uhler’s Sundragon dragonfly (Helocordulia uhleri).

Notice the dorsal hooks on abdominal segments seven through nine (S7-9). This distinctive character confirms the identity of the specimen as H. uhleri.

13 APR 2021 | Prince William County, VA | Uhler’s Sundragon (exuvia)

Another photo taken from the same view point, exposed and edited for more contrast, shows the three dorsal hooks a little more clearly than the preceding photo.

13 APR 2021 | Prince William County, VA | Uhler’s Sundragon (exuvia)

Knowing when good is good enough

A dear friend sent an article to me years ago entitled “Knowing when good is good enough.” I think she was trying to tell me something.

I tend to be a perfectionist. For example, I’m a man on a mission to take the best possible macro photographs of odonate larvae and exuviae given the limitations of my photography gear and small home studio.

Sometimes perfection is a road block that prevents me from shooting and posting photos that are more than serviceable for my purposes, in this case, informal instruction.

I did a quick Google search for the article from my friend. No luck, but I found one that’s close enough — you might even say one that’s good enough — for a little self-help.

None of the photographs in this blog post are perfect — not even close! But I published them anyway. Baby steps, Bob.

Related Resources

• How Do You Know What’s Good Enough? Can striving for perfection be freely chosen–not just compulsive behavior? by Leon F. Seltzer Ph.D., Psychology Today.
• Heliocordulia uhleri exuvia – a photo-illustrated identification guide by Walter Sanford.
• Uhler’s Sundragon dragonfly (emergent female) – a related blog post by Walter Sanford.

Copyright © 2021 Walter Sanford. All rights reserved.

Sumo Citrus still life

Have you seen/eaten Sumo Citrus? They’re easy to peel, seedless, and billed as “the sweetest orange.” Delicious, I say!

How I got the shots

I set up a tripod at a good distance from the subject for a 50mm lens. Then I switched cameras without moving the tripod. Each camera/lens combo was set for an aperture of f/8; other camera and flash settings varied as necessary. (See EXIF info for details regarding camera settings for each photo.)

Canon 5D Mark II

Canon EF 50mm f/1.8 II lens (“Nifty 50”), Godox X2TC, Godox TT685C plus Lastolite flash modifier.

18 March 2021 | BoG Photo Studio | Sumo Citrus

Fujifilm X-T1

Fujinon 18-55mm zoom kit lens set for 34mm (51mm, 35mm equivalent), Godox XProF, Godox TT685C plus Lastolite flash modifier.

18 March 2021 | BoG Photo Studio | Sumo Citrus

Fujifilm X-T3

Fujifilm 11mm extension tube, Fujinon XF80mm macro lens, Vello Off-Camera TTL Flash Cord, Godox X2TF, Godox TT685C plus Lastolite flash modifier.

18 March 2021 | BoG Photo Studio | Sumo Citrus

Sumo Citrus from Giant Food

Bernard Nimmons is the produce manager at the Giant Food located in Beacon Center. I sent a Facebook Messenger message to Bernard recently…

I need Sumo Oranges STAT! Are they back in stock?

The following selfie photo is Bernard’s reply to my message. Now you can see why I always say “Bernard puts the ‘Pro’ in Produce.”

Selfie photo used with permission from Bernard Nimmons.

Copyright © 2021 Walter Sanford. All rights reserved.

Answer key: Vernier calipers

The jaws of the caliper are spread apart 11.15 mm (7/16″), as shown by the following annotated photo.

08 MAR 2021 | Bog Photo Studio | analog Vernier caliper (close-up)

As it turns out, I used the calipers to measure the diameter of the barrel of a brass spigot used for photography clamps.

Product image courtesy B&H Photo.

Related Resource: Tools of the trade: Vernier calipers.

Copyright © 2021 Walter Sanford. All rights reserved.

Tools of the trade: Vernier calipers

A Vernier caliper is a useful tool for measuring things precisely. The caliper shown in the following photos is precise to 0.05 mm (1/128 in).

08 MAR 2021 | Bog Photo Studio | analog Vernier caliper

Some guides to the identification of odonate larvae and exuviae are measurement intensive. A caliper can be helpful for making measurements of a specimen quickly.

08 MAR 2021 | Bog Photo Studio | analog Vernier caliper (close-up)

Carolina Biological Supply Company sells both analog and digital calipers. Analog calipers are relatively inexpensive and work well. Digital calipers can cost at least five times more than their analog counterparts.

Carolina sells two models of analog Vernier calipers: one model is made of nickel-plated steel; the other is made of plastic. The metal caliper has sharp edges and points that can scratch surfaces easily; the plastic caliper won’t scratch most surfaces.

The metal model comes in a plastic pouch; the plastic model doesn’t. Advantage metal model, right? No! Both the metal caliper and its plastic pouch are covered in some type of lubricant that is both unnecessary and a chore to clean off the caliper. Can you tell I prefer the plastic model?

Learning by doing – How to read the Vernier scale

How to Read a Metric Vernier Caliper by WeldNotes.com (7:01) is an animated video that explains how to read the Vernier scale of an analog caliper. Watch the video, then test yourself to see whether you can determine how far the bigger jaws of the caliper are spread apart (in mm), as shown in the preceding close-up photo.

Be careful — the Vernier scale shown in the video is precise to 0.02 mm while the one shown in the photograph is precise to 0.05 mm. Here’s a hint: The jaws of the caliper are slightly more than 11 mm apart.

Please submit your answer as a comment on this blog post. Relax, you won’t see any spoilers because all comments must be approved by the blog administrator. (Hey, that’s me!)

Post update

The answer key for the caliper quiz is now online.

Copyright © 2021 Walter Sanford. All rights reserved.