Archive for the ‘Aperture’ Category

Arrowhead Spiketail (terminal appendages)

January 21, 2022

Arrowhead Spiketail dragonflies (Cordulegaster obliqua) were spotted along small streams at undisclosed locations in Fairfax County and Prince William County, Virginia USA.

Male and female Arrowhead Spiketails are similar in appearance. They can be differentiated based upon several field marks.

Male

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

07 JUL 2014 | Fairfax County | Arrowhead Spiketail (male)

Arrowhead male and female cerci are similar in appearance, and it can be challenging to see the epiproct clearly from some viewpoints. When in doubt whether an individual is male or female, look for indentations at the base of the hind wings of males.

07 JUL 2014 | Fairfax County | Arrowhead Spiketail (male)

Female

This individual is a female, as indicated by her rounded hind wings, terminal appendages, and prominent subgenital plate (ovipositor) at the tip of her abdomen.

21 MAY 2019 | PNC. Wm. County | Arrowhead Spiketail (female)

Although Arrowhead male and female cerci are similar in appearance, there is no mistaking the subgenital plate of female spiketails! It’s easy to see why “Spiketails” is the common name for Family Cordulegastridae.

21 MAY 2019 | PNC. Wm. County | Arrowhead Spiketail (female)

So the take-away is simple: If you see a subgenital plate then the individual is definitely female; if not, then it’s probably a male.

Copyright © 2022 Walter Sanford. All rights reserved.

Post update: What is it?

January 18, 2022

The mystery item featured in my last blog post is a Beetle Spin® 1/8 oz fishing lure.

Beetle Spin® 1/8 oz fishing lure.

Perhaps the bigger mystery is how the fishing lure ended up where I found it, stuck in the bark of a tree (about head height) quite a distance from a small stream that might be fish-less. There was no fishing line attached to the lure. Anyway, there it was.

Beetle Spin® is one of the classic all-purpose fishing lures that is a nice addition to my tackle box.

Copyright © 2022 Walter Sanford. All rights reserved.

Dark and moody

November 19, 2021

I spotted an emergent Uhler’s Sundragon (Helocordulia uhleri) during a photowalk along a mid-size stream at an undisclosed location in Prince William County, Virginia USA. The following photograph shows the exuvia from which the teneral adult emerged.

13 APR 2021 | PNC. Wm. County, VA | Uhler’s Sundragon | exuvia (ventral)

In the opinion of the author, larvae (nymphs)/exuviae from Family Corduliidae (Emeralds) and Family Libellulidae (Skimmers) can be challenging to differentiate and identify to the family level.

One way to differentiate Emerald from Skimmer larvae/exuvia is to look for a “ventromedial groove” in the prementum: it’s probably Corduliidae (Emeralds) if there is a ventromedial groove; it’s probably Libellulidae if there isn’t.

Look closely at a version of the preceding photo that was reformatted, rotated, and cropped to show an enlarged view of the prementum. You should notice a ventromedial groove on the basal half of the prementum, indicating this specimen is a member of Family Corduliidae (Emeralds).

13 APR 2021 | PNC. Wm. County, VA | Uhler’s Sundragon | exuvia (ventral)

Three raised structures on the underside of the prementum remind me of the hood ornament on a 1949 Lincoln automobile. (No, I wasn’t alive in 1949!)

Related Resources

Tech Tips

One reason I underexposed the photo is to add definition to the ventromedial groove and avoid overexposing the black background.

I prefer a white background for photographing odonate exuviae. Using a black background proved to be more challenging than I expected. More later in a follow-up blog post.

Copyright © 2021 Walter Sanford. All rights reserved.

Cordulegaster sp. larva

October 22, 2021

Odonates are aquatic insects. They spend most of their life as larvae (nymphs) 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.

This post features annotated images of a larva (nymph) from the Family Cordulegastridae (Spiketails) that was collected and reared by Bob Perkins. The larva died before it metamorphosed into an adult.

The distinctive jagged crenulations on the face mask of spiketails are unmistakeable!

Cordulegaster sp. larva (preserved specimen) | face-head

This individual is a female, as indicated by her developing ovipositor that can be seen on the ventral side of the specimen along the boundary between abdominal segments eight and nine (S8, S9).

Cordulegaster sp. larva (female) | ventral view

The presence of a ventromedial groove in the prementum is a reliable field mark for larvae/exuviae in Family Corduliidae (Emeralds). Some species of larvae/exuviae in other families of dragonflies, such as Family Cordulegastridae (Spiketails), feature a ventromedial groove in the prementum. In this case, the presence of a ventromedial groove does not indicate this specimen is an Emerald.

Most odonate larvae go through 10-13 stages of development known as “instars.” The author lacks sufficient experience to identify the instar of this specimen, although it appears to be one of the later stages as indicated by its well-developed wing pads, shown below.

Post Update: According to Ken Tennessen, author of Dragonfly Nymphs of North America: An Identification Guide, F-0 is the instar of this specimen (final instar). Thanks, Ken!

Cordulegaster sp. larva (female) | dorsal view

Larvae (nymphs)/exuviae in Family Cordulegaster (Spiketails) are burrowers, as indicated by the dirty, sediment-covered dorsal side and relatively clean ventral side of this specimen.

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Comet Darner exuvia: annotated images

October 8, 2021

My last blog post was a “sketch pad” of test shots of an exuvia from a Comet Darner dragonfly (Anax longipes) collected by Stanley Caveney on 19 July 2021 from a pond at MeadowWoods in West Elgin, Ontario, Canada. All of the shots in that post are unedited JPGs straight from my camera. This post features edited versions of the RAF (raw) files from that photo shoot, including some images with value-added annotations.

Lateral view

I considered annotating the first photo but decided to allow it to stand on its own as the latest addition to my Odonart© Portfolio.

Comet Darner (Anax longipes) | exuvia (lateral)

Ventral view

I used Adobe Photoshop to create a composite image that features the best parts of two photos from the sketch pad.

This specimen is from a male Comet Darner, as indicated by its vestigial primary- and secondary genitalia. The inset photo shows a clear view of the vestigial hamuli (secondary genitalia) that are partially obscured in the background photo.

Comet Darner (Anax longipes) | exuvia (ventral)

Prementum

The last photo shows a closer view of the mentum, a two-segment hinged “jaw” that is used to grab food: the prementum is the segment of the labium closer to the mouth; the postmentum is the segment closer to the base of the head. Only the prementum can be seen in the following photo.

Comet Darner (Anax longipes) | exuvia (prementum)

The preceding annotated image of the prementum includes labels for the moveable hooks (2 of 2) and palpal lobe (1 of 2). Notice that A. longipes palpal lobes are squared off, in contrast with the more rounded shape of the labial palps of Common Green Darner (Anax junius).

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

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

September 24, 2021

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

Copyright © 2021 Walter Sanford. All rights reserved.

Test shots: Didymops transversa exuvia

September 21, 2021

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 are bottom dwellers, as indicated by the dirty, sediment-covered 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

Copyright © 2021 Walter Sanford. All rights reserved.

Test shots

September 17, 2021

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.

Multimeter test results: GyroVu continuous power adapter for Panasonic

September 14, 2021

Eureka! I found my RadioShack Digital Multimeter.

In a recent blog post, I said I would like to use a multimeter to test the actual voltage output of the GyroVu USB TO PANASONIC DMC-GH2 (DMW-BLC12) BATTERY 40″ CABLE w/ 3.1A USB POWER SUPPLY that provides continuous power for my Panasonic Lumix DMC-FZ300 superzoom bridge camera. This blog post features the results from that test and more.

Panasonic rechargeable Li-ion camera battery

The Panasonic Lumix DMC-FZ300 uses a Panasonic DMW-BLC12 Rechargeable Lithium-Ion Battery (7.2V, 1200mAh), shown below.

Panasonic DMW-BLC12PP 7.2V Li-ion battery (front).

The positive and negative terminals of the battery are marked on the back of its case.

Panasonic DMW-BLC12PP 7.2V Li-ion battery (back).

I set the multimeter to measure voltage and touched the black test lead to the negative (-) terminal, then touched the red test lead to the positive (+) terminal. The LCD on the multimeter displayed a voltage of 07.29V, as shown below. That’s good!

Voltage output from Panasonic 7.2V Li-ion battery.

GyroVu continuous power adapter

Next, the GyroVu “USB Charger” (shown below, to the lower-left) was plugged in a 120V AC electrical outlet. The GyroVu dummy battery was connected to the 3100mA USB connector on the GyroVu USB Charger.

Although the positive and negative terminals of the dummy battery aren’t marked on its case, they are in the same places as on the Li-ion battery.

Once again I set the multimeter to measure voltage and touched the black test lead to the negative (-) terminal, then touched the red test lead to the positive (+) terminal. The LCD on the multimeter displayed a voltage of 08.36V, as shown below.

Voltage output from GyroVu dummy battery for Panasonic.

GyroVu says the output voltage of the dummy battery is 8.0V, so 8.36V seems to be within specs.

For what it’s worth, the Owner’s Manual for the model of RadioShack Digital Multimeter that I used specifies the accuracy of the multimeter is +/-0.8% of the reading, or in this case +/-0.07V.

Therefore I think it’s safe to say the GyroVu dummy battery has a slightly higher voltage than the Panasonic Li-ion battery. Is the higher voltage cause for concern?

Perhaps the more important question is whether amperage matters more than voltage. Regular readers of my blog might recall that I used my Drok USB Tester to measure an amperage of 0.45A drawn by the camera when it was connected to the GyroVu adapter and powered on. Is that amperage safe for the camera?

I’m not sure of the answer to either question, although I am certain further investigation is required.

Anker external power bank

Each GyroVu “dummy battery” adapter cable features a USB connector that can be used to connect your digital camera to an external power bank such as the Anker PowerCore+ 26800 PD 45W), shown below.

Product image courtesy AnkerDirect.

My Drok USB Tester was connected to one of two USB ports on the Anker power bank. The output voltage of the power bank was 5V, same as the GyroVu “USB Charger.”

The GyroVu dummy battery was plugged into one of two USB ports on the Anker power bank. Once again I set the multimeter to measure voltage and touched the black test lead to the negative (-) terminal, then touched the red test lead to the positive (+) terminal. The LCD on the multimeter displayed a voltage of 08.36V (shown above) — exactly the same as when I used the GyroVu “USB Charger” as the source of continuous power.

Voltage output for GyroVu dummy battery for Panasonic connected to Anker PowerCore+ 26800 PD 45W.

At this point I think it’s safe to say the Anker power bank is safe to use as a source of continuous power for my Panansonic Lumix DMC-FZ300 camera, that is, assuming the ~8.0V output of the GyroVu dummy battery isn’t a problem.

Related Resources

This blog post is one in a series of posts related to continuous AC power and long-lasting battery power for select Canon, Fujifilm, and Panasonic digital cameras.

Copyright © 2021 Walter Sanford. All rights reserved.

Anax junius versus Anax longipes

September 10, 2021

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

Copyright © 2021 Walter Sanford. All rights reserved.


%d bloggers like this: