Blog posts related to instar

A while ago I created a series of single-topic blog posts related to instar. I just converted the Web versions of those blog posts to PDFs (Portable Document Format).

The PDF version of each blog post is available in two “flavors”: an interactive version (with Internet access), meaning the embedded hyperlinks work as expected; and a non-interactive version. Both versions are ad-free.

• “How to estimate instar”: Web version; interactive PDF version, Apple macOS and “Safari” (119 KB); non-interactive PDF version, Apple iOS and “Safari” (533 KB).
• “How to estimate instar, revisited”: Web version; interactive PDF version, Apple macOS and “Safari” (474 KB); non-interactive PDF version, Apple iOS and “Safari” (2.5 MB).
• “How to estimate instar using Photopea”: Web version; interactive PDF version, Apple macOS and “Safari” (154 KB); non-interactive PDF version, Apple iOS and “Safari” (308 KB).
• “Determining final instar the Cham way”: Web version; interactive PDF version, Apple macOS and “Safari” (195 KB); non-interactive PDF version, Apple iOS and “Safari” (1.3 MB).

Related Resources

• How to convert a Web page to PDF – a blog post by Walter Sanford
• Another way to convert a Web page to PDF – another blog post by Walter Sanford

Copyright © 2022 Walter Sanford. All rights reserved.

Identification guides for Sable Clubtail

Identification guides for Sable Clubtail dragonfly (Stenogomphurus rogersii) were created for both adult and larva/nymph forms. (Remember, a well-preserved odonate exuvia is a perfect model of the final instar larva.)

Sable Clubtail has a limited range and is classified as rare to uncommon.

The adult flight period is from May 21 to July 24 in the Commonwealth of Virginia. Source Credit: “CHECKLIST OF THE DRAGONFLIES AND DAMSELFLIES OF VIRGINIA, April 2017 and April 2020 updates” by Dr. Steve Roble, Staff Zoologist at the Virginia Department of Conservation and Recreation, Division of Natural Heritage.

Adult

Apple macOS and Safari (interactive)

Apple macOS and “Safari” were used to convert the Web page version of “Field marks for identification of S. rogersii” to PDF (Portable Document Format). The PDF version of the same Web page is 351 KB, ad-free, and is interactive (with Internet access), meaning the embedded hyperlinks work as expected.

Apple iOS and Safari (non-interactive)

Apple iOS and “Safari” were used to convert the Web same page to PDF. The PDF version is 5.4 MB, ad-free, and is not interactive.

(See complete PDF version of “Field marks for identification of S. rogersii.”)

The preceding screenshot shows what the output looks like.

Apple “Photos” can be used to view PDFs on iOS devices. For macOS devices, Apple “Preview” can be used to open the complete PDF version; select “View / Actual Size” and resize the window as necessary. And of course PDFs can be opened using a Web browser.

Exuvia

Apple macOS and Safari (interactive)

Apple macOS and “Safari” were used to convert the Web page version of “Stenogomphurus rogersii exuvia” to PDF. The PDF version of the same Web page is 692 KB, ad-free, and is interactive (with Internet access).

Apple iOS and Safari (non-interactive)

Apple iOS and “Safari” were used to convert the Web same page to PDF. The PDF version is 4.8 MB, ad-free, and is not interactive.

(See complete PDF version of “Stenogomphurus rogersii exuvia.”)

The preceding screenshot shows what the output looks like.

Copyright © 2022 Walter Sanford. All rights reserved.

How to estimate instar using Photopea

In two recent blog posts (see Related Resources, below), I showed how Adobe Photoshop can be used to make measurements that enable you to estimate the instar of odonate larvae (nymphs).

The process works well, that is, as long as you have Photoshop. Does that mean you’re out of luck if you don’t? In a word, no.

“Photopea” is a free alternative to Adobe Photoshop. Photopea is a Web-based clone of Photoshop — Photopea doesn’t do everything Photoshop does but it can be used to make measurements on photos using a workflow similar to the one I described in detail in a blog post entitled “How to estimate instar.”

Practical example using Photopea

Open Photopea in a Web browser: www.photopea.com (For what it’s worth, I prefer “Google Chrome.”) Since Photopea is Web-based, it runs on desktop computers, laptop computers, tablets, and smart phones.

In order to make this tutorial as simple as possible I went to the Photopea menu bar, navigated to File / New… and created the default blank white canvas, shown below. Note: You should go to File / Open… and navigate to a photo of an odonate larva.

Use the Photopea “Ruler Tool” to measure the length (in pixels) of two line segments: HwL (Hind wing Length); and HW (Head Width). If you don’t know how to measure “HwL” and “HW” then please refer to “How to estimate instar” for detailed, step-by-step instructions.

Right-click on the Eyedropper Tool — located in the left sidebar of the main window, as shown below — and select the Ruler Tool.

Click and drag line segment HwL, such as the sample line shown below. Record the length of the line, in pixels. Click the “Clear” button (optional) and repeat the same process for line segment HW (not shown).

Do the math to calculate instar equivalent and voilà, the result is a number that can be used to estimate instar based upon Ken Tennessen’s average instar equivalents. Again, please refer to “How to estimate instar” for detailed, step-by-step instructions.

Related Resources

• Dragonfly Nymphs of North America: An Identification Guide, by Ken Tennessen. Section 2.5.1 Determining Instar, pp. 27-28.
• A Method for Determining Stadium Number of Late Stage Dragonfly Nymphs (Odonata: Anisoptera), by Kenneth Tennessen.
• How to estimate instar
• How to estimate instar, revisited
• Learn Photopea

Copyright © 2021 Walter Sanford. All rights reserved.

How to estimate instar, revisited

I’m the founder and co-administrator of the Odonate Larvae and Exuviae Facebook group. Friday, 12 November 2021 was the two-year anniversary of the group. As of this writing there are approximately 1,700 members in the group, including people from around the world.

For example, Abiodun Matthew Adedapo from Nigeria. Abiodun began posting to the group relatively recently, sharing information and photos related to his research. Sincere thanks to Abiodun for permission to repurpose two of his photos for another mini-lesson on how to estimate instar.

What is the instar? Not F-0.

The equation for instar equivalent is as follows.

Instar equivalent = HwL / HW

Where HwL is Hind wing Length and HW is Head Width.

 

Photo used with written permission from Abiodun Matthew Adedapo.

I used the Adobe Photoshop “Ruler Tool” to measure the number of pixels along the two double-headed white arrows shown in the preceding annotated image of a preserved specimen collected and photographed by Abiodun.

HwL is ~132.6 pixels. HW is ~195.12 pixels.

Instar equivalent = 132.6 pixels / 195.12 pixels

The units cancel, so the answer is ~0.68 — close to Ken Tennessen’s  average value for F-1 (final instar minus one).

Abiodun reported the instar as F-2, based upon in situ observations of a cohort of larvae (nymphs) from Family Gomphidae (Clubtails).

For my purpose, it doesn’t matter whether the actual instar is either F-1 or F-2 — the important take-away is we know the instar is not F-0, the final instar. This provides an opportunity to mention a simpler way to estimate final instar.

Larvae in the final stage can be recognized by the length of the wing buds which cover the fourth abdominal segment. Source Credit: Field Guide to the larvae and exuviae of British Dragonflies, by Steve Cham, p. 30.

Look closely at the first annotated image. Notice the length of the wing buds/pads doesn’t reach the fourth abdominal segment (S4) of the specimen therefore this larva is not in its final instar.

Thanks to Freda van den Broek for sharing this method with me!

F-0 (final instar)

The last annotated image shows part of a different larva also collected and photographed by Abiodun. Notice the length of the wing buds/pads does reach S4, therefore this larva is in its final instar.

Photo used with written permission from Abiodun Matthew Adedapo.

Related Resources

• How to estimate instar, a blog post by Walter Sanford.
• How to estimate instar using Photopea

Copyright © 2021 Walter Sanford. All rights reserved.

Cordulegaster sp. larva (dorsal view)

This post features a focus-stacked composite image that shows a dorsal view of an odonate larva/nymph from the Family Cordulegastridae (Spiketails) that was collected and reared by Bob Perkins. The larva died before it metamorphosed into an adult.

Cordulegaster sp. larva (female) | dorsal view

Most 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.

Related Resources

• Test shot: Cordulegaster sp. larva
• Cordulegaster sp. larva (ventral view)

Tech Tips

12 photos were used to create the focus stack. A single focus point was positioned over select anatomical features; photos were taken at each point of interest.

The following equipment was used to shoot all of the photographs for the focus-stacked composite image, shown above: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tube; Canon EF100mm f/2.8L Macro lens (set for manual focus); and Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and several external flashes set for “Slave” mode including Canon 580 EX- and Canon 580EX II Speedlites and a Godox TT685C Thinklite TTL Flash fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier.

Auto power-off was disabled for the camera and all external flash units.

Adobe Photoshop CC 2017 was used to create the focus-stacked composite image, as well as spot-heal and sharpen the final output.

Copyright © 2019 Walter Sanford. All rights reserved.

Cordulegaster sp. larva (ventral view)

Bob Perkins collected and reared an odonate larva/nymph from the Family Cordulegastridae (Spiketails). The larva died before it metamorphosed into an adult.

This post features a focus-stacked composite image that shows a ventral view of the preserved larva; a composite image showing the dorsal view will be published in my next blog post.

Cordulegaster sp. larva (female) | ventral view

This individual is a female, as indicated by her rudimentary ovipositor that can be seen on the ventral side of the specimen along the boundary between abdominal segments eight and nine (S8-9). Do you see it?

Related Resources

• Test shot: Cordulegaster sp. larva.
• Cordulegaster sp. larva (dorsal view)

Tech Tips

Nine (9) photos were used to create the focus stack. A single focus point was positioned over select anatomical features; photos were taken at each point of interest.

The following equipment was used to shoot all of the photographs for the focus-stacked composite image, shown above: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tube; Canon EF100mm f/2.8L Macro lens (set for manual focus); and Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and several external flashes set for “Slave” mode including Canon 580 EX- and Canon 580EX II Speedlites and a Godox TT685C Thinklite TTL Flash fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier.

Auto power-off was disabled for the camera and all external flash units.

Adobe Photoshop CC 2017 was used to create the focus-stacked composite image, as well as spot-heal and sharpen the final output.

Copyright © 2019 Walter Sanford. All rights reserved.

“Generic Baskettail” (definitely not a Cruiser)

A larva/nymph in the Family Corduliidae (Emeralds) was collected by Bob Perkins on 02 December 2017 from a pond in Orange Park, Florida (USA). The larva died before it metamorphosed into an adult.

As you can see by looking at a close-up image of the face-head at 3x magnification, there is no horn on the face of the specimen. Therefore this individual is not a member of Family Macromiidae (Cruisers), as I speculated in my last blog post.

“Generic Baskettail” larva (preserved specimen) | face-head

Knowing the limits of our expertise

Although I still need to key out the specimen carefully, at this point I’m certain Bob is correct — the larva is a member of the Family Corduliidae (Emeralds). The question that remains unanswered is “Which genus/species?” We may never know the answer, as Bob and I have reached the limit of our experience and expertise.

I did a quick scan of Paulson’s [book], looking at the Emerald Family. Here, according to the range maps, are the possibilities for Orange Park [FL]. I believe you can see why I stopped at “generic basketttail.” Source Credit: Bob Perkins.

• Slender Baskettail (Epitheca costalis)
• Common Basketball (Epitheca cynosura)
• Prince Baskettail (Epitheca princeps)
• Mantled Baskettail (Epitheca semiaquea)
• Sepia Baskettail (Epitheca sepia)
• Florida Baskettail (Epitheca stella)
• Alabama Shadowdragon (Neurocordulia alabamensis)
• Umber Shadowdragon (Neurocordulia obsoleta)
• Fine-lined Emerald (Somatochlora filosa)
• Coppery Emerald (Somatochlora georgiana)
• Mocha Emerald (Somatochlora linearis)

What do you think the identity is? Most of the items in the preceding species list feature links to photos of odonate larvae/exuviae. See the links to BugGuide from the scientific names in the list.

Related Resource: Test shots: “Generic Baskettail?”

Tech Tips

Four (4) photos were used to create the preceding focus-stacked composite image. A single focus point was positioned over the face, between the antennae. At a magnification ratio of 3:1, it’s difficult to manually focus on a single point — the slightest movement around the macro rig changes focus unintentionally. A simple work-around for this problem is to take several shots of the same focus point and create a composite image of the photos.

The following equipment was used to shoot the preceding composite image: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (set for f/16 at 3x); a Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and a single external flash set for “Slave” mode — a Godox TT685C Thinklite TTL Flash fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier. A Sunpak LED-160 Video Light was used to add fill light to the top of the subject.

Auto power-off was disabled for the camera and external flash units.

Adobe Photoshop CC 2017 was used to create the focus stack, as well as spot-heal and sharpen the final output.

Copyright © 2019 Walter Sanford. All rights reserved.

Test shots: “Generic Baskettail?”

A larva/nymph in the Family Corduliidae (Emeralds) was collected by Bob Perkins on 02 December 2017 from a pond in Orange Park, Florida (USA). The larva died before it metamorphosed into an adult.

Test shots of this beautifully preserved specimen were taken using a small-ish aperture of f/11 for greater depth of field. The following photos are “one-offs,” that is, not composite images.

Dorsal

A single focus point — located on the thorax (specifcally, the “shoulder pad” along the right side of the body) — was used to shoot this photo. The specimen has enough “relief” that focus on the wing pads and dorsal hooks is slightly soft. This view of the larva is a good candidate for focus-stacking.

The terminal appendages (cerci, epiproct, paraprocts) are shown clearly in the following photo.

“Generic Baskettail” larva (preserved specimen) | Orange Park, FL USA

Bob’s best guess of the identity of the specimen is Epitheca sp., either Common Baskettail (Epitheca cynosura) or Prince Baskettail (Epitheca princeps).

Whenever I see an odonate larvae/exuviae with long legs, my first thought is Family Macromiidae (Cruisers). Then I check for a horn on top of the head, a key field mark for Cruisers. Look closely at the dorsal view of the larva and I think you’ll agree with me there appears to be a horn on the head. I would like to take close-up photos of the head and key out the specimen in order to determine its identity. In the meantime, my best guess is Stream Cruiser (Didmops transversa) as indicated by the lateral spines on abdominal segment nine (S9) and the absence of a dorsal hook on S10.

Ventral

The ventral side of the specimen has almost no “relief,” so a “one-off” focused on the thorax looks fairly good from head-to-tail.

“Generic Baskettail” larva (preserved specimen) | Orange Park, FL USA

Related Resource: “Generic Baskettail” (definitely not a Cruiser)

Tech Tips

The following equipment (shown below) was used to shoot the preceding photos: Fujifilm X-T1 digital camera; Fujifilm MCEX-16 extension tube; Fujinon XF80mm macro lens; Godox XProF TTL Wireless Flash Trigger for Fujifilm cameras; Godox TT685F Thinklite TTL Flash for Fujifilm Cameras; Godox TT685C Thinklite TTL Flash for Canon Cameras fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier; and a Canon 580EX II Speedlite mounted on a Godox X1R-C TTL Wireless Flash Trigger Receiver for Canon. A new Godox TT685O Thinklite TTL Flash for Olympus/Panasonic Cameras was added to an array of radio-controlled external flash units used to light the specimen. All flashes were set for Manual Mode at 1/128 power.

Adobe Photoshop CC 2017 was used to spot-heal and sharpen the final output.

Copyright © 2019 Walter Sanford. All rights reserved.

Test shot: Cordulegaster sp. larva

Bob Perkins collected and reared a larva/nymph from the Family Cordulegastridae (Spiketails). The larva died before it metamorphosed into an adult.

Test shots of this beautifully preserved specimen (Cordulegaster sp.) were taken using a relatively small aperture of f/16 for greater depth of field. The following photo is a “one-off,” that is, not a composite image.

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

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.

Most 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.

Related Resources

• Cordulegaster sp. larva (ventral view)
• Cordulegaster sp. larva (dorsal view)
• Odonate Exuviae – a hyperlinked list of identification guides to many species of odonate exuviae from seven families of dragonflies and three families of damselflies.

Tech Tips

The following equipment was used to shoot the preceding photo: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (set for 3x); and Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and several external flashes set for “Slave” mode including Canon 580 EX- and Canon 580EX II Speedlites and a Godox TT685C Thinklite TTL Flash fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier. A Sunpak LED-160 Video Light was used to light the underside of the white plastic posing “stage.”

Auto power-off was disabled for the camera and all external flash units.

Adobe Photoshop CC 2017 was used to spot-heal and sharpen the final output.

Copyright © 2019 Walter Sanford. All rights reserved.

More test shots: Stylogomphus albistylus exuvia

This blog post features another focus-stacked composite image of an Eastern Least Clubtail dragonfly (Stylogomphus albistylus) exuvia from an odonate nymph that Bob Perkins collected and reared.

11 photos were used to create this focus stack. My camera is set for spot focus, meaning one-area focus for each photo. A single focus point was positioned manually somewhere on the face-head in all 11 photos.

From this viewpoint, the large, dish-shaped antennae remind me of wooden spoons (with short handles).

Eastern Least Clubtail (Stylogomphus albistylus) | exuvia (face-head)

This is the first time I shot some photos in portrait mode using my new 3 Legged Thing QR11-LC Universal L-Bracket (Orange) mounted on my Canon 5D Mark II DSLR camera. I’m sold!

3 Legged Thing QR11-LC Universal L-Bracket (Orange).

Related Resources

• Test shots: Stylogomphus albistylus exuvia
• Focus-stacking with CamRanger

Tech Tips

The following equipment was used to shoot all of the photographs for the focus-stacked composite image of the exuvia: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tube; Canon EF100mm f/2.8L Macro lens (set for manual focus); and Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and several external flashes set for “Slave” mode including Canon 580 EX- and Canon 580EX II Speedlites and a Godox TT685C Thinklite TTL Flash fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier.

Adobe Photoshop CC 2017 was used to create the focus-stacked composite image, as well as spot-heal and sharpen the final output.

I used my Panasonic Lumix DMC-FZ150 superzoom camera and a handheld Canon 580EX Speedlite fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier to shoot the photo of my Canon 5D Mark II.

More Related Resources

• 3 Legged Thing QE11-LC Universal L-Bracket, a product review by Walter Sanford.
• L Brackets: Two Minute Tips with David Bergman, by Adorama (2:46)

Copyright © 2018 Walter Sanford. All rights reserved.