Archive for the ‘natural science’ Category

Which family is it?

November 29, 2022

An odonate exuvia was collected by Cindy Haddon Andrews on 03 September 2022 along the James River, near the Maidens Boat Landing in Powhatan County, Virginia USA. This specimen is from a damselfly in Suborder Zygoptera.

Pattern recognition can be used to tentatively identify damselfly larvae/exuviae to the family level: the shape of the prementum is characteristic for each of the three families found in the mid-Atlantic region of the United States of America.

Your mission, should decide to accept it, is to identify the family to which the following damselfly exuvia belongs.

03 SEP 2022 | Powhatan County, VA USA | (exuviaventral side)

The camera lens was manually focused on the prementum, located near the anterior end of the exuvia.

Here is the same photo rotated 90° clockwise.

03 SEP 2022 | Powhatan County, VA USA | (exuviaventral side)

If you think you know the family, then please leave a comment. The correct answer will be revealed in a post update.

Related Resource: How to Identify Damselfly Exuviae to Family – a photo-illustrated identification guide by Walter Sanford.

Copyright © 2022 Walter Sanford. All rights reserved.

Archilestes grandis exuvia (female)

November 25, 2022

An odonate exuvia from a Great Spreadwing damselfly (Archilestes grandis) was collected by Edgar Spalding at a small private pond in Middleton, Wisconsin USA.

SEP 2022 | Middleton, WI | Archilestes grandis (exuvia, ventral side)

External gills (3), highlighted by a blue rectangle in the following annotated image, indicate the exuvia is from a damselfly in Suborder Zygoptera.

The camera lens was manually focused on the prementum, located near the anterior end of the exuvia (highlighted by a red rectangle). The overall shape of the prementum indicates this specimen is from Family Lestidae (Spreadwings); the unique shape of the palpal lobes (highlighted by a purple rectangle) indicates Genus Archilestes.

There are two species in Genus Archilestes in North AmericaArchilestes californicus; and Archilestes grandis. I think it’s reasonable to infer this individual is A. grandis since Wisconsin is far out of range for A. californicus.

SEP 2022 | Middleton, WI | Archilestes grandis (exuvia, ventral side)

This individual is a female, as indicated by the rudimentary ovipositor located on the ventral side of its abdomen, near the posterior end (highlighted by a green rectangle in the preceding annotated image).

Related Resources

Copyright © 2022 Walter Sanford. All rights reserved.

Iberian odonate larvae

September 16, 2022

During late-October 2021, I was contacted by Miguel A. Conesa-García, PhD, Profesor Tutor Biología, Diversidad Animal, Ciencias Ambientales, UNED-Málaga.

Miguel was working on finishing the second edition of his book about odonate larvae in the Iberian Peninsula (Spain and Portugal). When Miguel was almost finished, an adult male Wandering Glider dragonfly (Pantala flavescens) was spotted in Spain. P. flavescens is a new species of odonate for the region, so Miguel decided to add the new discovery to the species list in his book.

Cover photo, courtesy Amazon Books.

The following screen capture shows the search string I used to find the book on Amazon.

Screen capture, Amazon Books.

The book is richly illustrated with beautiful photos and diagrams. It’s abundantly evident I could learn a lot from the book — I wish there were an English Edition!

Miguel requested permission to use a photo of a Wandering Glider exuvia in my photoblog, published on 14 November 2018. I was, of course, willing to help.

Page excerpt from Miguel’s book, featuring my photo.

I’m mentioned in the acknowledgements at the end of the book. Regrettably my first name is misspelled and the Web address cited is no longer current. I took the liberty of annotating the page from Miguel’s book to provide the correct information.

Acknowledgements, p. 539 (annotated).

Acknowledgements, p. 539 (original).

Migratory Dragonflies

Wandering Glider is one of at least five major species of dragonflies known to be migratory in North America. P. flavescens is the only species of odonate known to occur on every continent except Antarctica.

The exuvia that I photographed is the “cast skin” from an odonate larva (nymph) that was collected in the field by Andy Davidson, a graduate student at Virginia Commonwealth University in Richmond, Virginia USA. Andy reared the larva in the laboratory as part of a research project entitled “Predator-Prey Interactions in a Changing World.”

Part of the value in rearing odonate larvae in the laboratory is knowing with certainty that an exuvia is from a particular species. This is perhaps the reason that Miguel chose to use my photo.

Related Resources

Copyright © 2022 Walter Sanford. All rights reserved.

Pantala versus Tramea exuviae/larvae

August 12, 2022

Sometime during the late 1950s or early 1960s, my father bought a new car. That was a big deal in our family. My family was poor, although I didn’t realize it when I was a young boy. We couldn’t afford a new car very often. I don’t remember many details about the car other than it was a sky blue Plymouth with tail fins. Big tail fins! My best guess is the car was a four-door Plymouth Fury, sold from 1957 – 1960.

Some odonate exuviae/larvae remind me of the tail fins on my father’s Plymouth automobile. Go figure. Anyway, pattern recognition can be used to make it a little easier to identify exuviae. For example, when I see an exuvia with long “tail fins,” my first thought is it’s probably from one of two genera, possibly three: genus Pantala; genus Tramea; or maybe genus Celithemis.

Dichotomous keys

The following couplet from Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz, can be used to differentiate exuvia from Genus Pantala and Genus Tramea.

p. 37, Key to the Genera of the Family Libellulidae
12a – Superior abdominal appendage (epiproct) as long as, or longer than inferiors [paraprocts]. Pantala
12b – Superior abdominal appendage (epiproct) shorter than inferiors [paraprocts]. Tramea

Soltesz, p. 39.

Soltesz, p. 40.

Soltesz, p. 41.

Genus Pantala (Rainpool Gliders)

The genus Pantala includes two (2) species in North America: Spot-winged Glider (Pantala hymenaea); and Wandering Glider (Pantala flavescens).

Spot-winged Glider and Wandering Glider larvae/exuviae look similar. The lateral spines on abdominal segment nine (S9) are noticeably shorter for P. hymenaea (shown left) than P. flavescens (shown right) — a key field mark that can be used to differentiate the two species.

Genus Tramea (Saddlebags)

The genus Tramea includes seven (7) species in North America. Two of those species are found commonly in the Commonwealth of Virginia: Black Saddlebags (Tramea lacerata); and Carolina Saddlebags (Tramea carolina).

Carolina Saddlebags

A Carolina Saddlebags dragonfly (Tramea carolina) larva was collected by Andy Davidson near Richmond, Virginia USA, and reared to maturity. Andy saved the exuvia after emergence.

A vertical white line marks the mid-dorsal length of abdominal segment nine (S9), as shown in the following annotated image; the vertical black line labeled “mid-dorsal length” is the same length as the white line. Notice the lateral spines of abdominal segment nine (S9) are much longer than its mid-dorsal length.

(See a full-size version of the original photo, without annotation.)

One of the keys to identifying skimmer dragonflies to the species level is to carefully examine the anal pyramid (S10), including the cerci (sing. cercus), epiproct, and paraprocts. Notice the epiproct is shorter than the paraprocts.

There is a lot of “seaweed” (aquatic vegetation) clinging to the exuvia, especially noticeable at the posterior end. Some collectors like to clean their specimens; I prefer to photograph them “as is.”

Black Saddlebags

Athough adult Black Saddlebags dragonflies (Tramea lacerata) are relatively common in Virginia, the author has never seen an exuvia from this species.

Genus Celithemis (Pennants)

The genus Celithemis includes eight (8) species in North America. The author has a specimen from only one of these species in his collection.

Calico Pennant dragonfly (Celithemis elisa) evuvia was collected by Sue and John Gregoire at Kestrel Haven Migration Observatory. For more than a decade, Sue and John have closely monitored the annual emergence of a large population of C. elisa at their farm pond.

Notice the long lateral spines that look similar to larvae/exuviae in genus Pantala and genus Tramea.

Related Resources

Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz.

  • p. 36 = Key to the Genera of Family Libellulidae
  • p. 37 = Pantala, Tramea
  • p. 39 = Key to the species of genus Pantala: hymenaea; flavescens
  • p. 41 = Key to the species of genus Tramea: carolina; lacerta

A Checklist of North American Odonata – Including English Name, Etymology, Type Locality, and Distribution, by Dennis R. Paulson and Sidney W. Dunkle.

Copyright © 2022 Walter Sanford. All rights reserved.

Kaizen

August 2, 2022

In Japanese, the word “kaizen” literally means improvement.

The Japanese word kaizen means ‘change for better,’ with the inherent meaning of either ‘continuous’ or ‘philosophy’ in Japanese dictionaries and in everyday use. The word refers to any improvement, one-time or continuous, large or small, in the same sense as the English word improvement. Source Credit: Kaizen, Wikipedia.

I wonder whether regular readers of my blog have noticed that many posts are updated and/or improved after they are posted. And so it is with the Identification Guide for Family Macromiidae (Cruisers) in Virginia that was published recently.

We corrected a typo (changed “boarder” to “border”) that spell-check missed, added a pointer to a range map for the two subspecies of Swift River Cruiser (see Related Resources), and updated the interactive version of the PDF (already published).

Finally we created a new, non-interactive version of the PDF. The following screenshot shows what the new document looks like.

(See the complete, non-interactive PDF version of the ID guide.)

Related Resources

Copyright © 2022 Walter Sanford. All rights reserved.

Blog posts related to instar

July 29, 2022

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

Copyright © 2022 Walter Sanford. All rights reserved.

Identification Guide for Family Macromiidae (Cruisers) in Virginia

July 15, 2022

There are two (2) genera and five (5) species in Family Macromiidae (Cruisers) that can be found in the Commonwealth of Virginia.

Stream Cruiser (Didymops transversa). MAR 26 – SEP 11.

Allegheny River Cruiser (Macromia alleghaniensis). JUN 4 – AUG 27.
Swift River Cruiser (Macromia illinoiensis) MAY 08 – OCT 10. [This species includes two subspecies: Macromia illonoiensis illinoiensis; and Macromia illinoiensis georgina.]
Mountain River Cruiser (Macromia margarita). MAY 25 – JUN 15.
Royal River Cruiser (Macromia taeniolata). MAY 15 – OCT 10.

Source Credits: A Checklist of North American Odonata
Including English Name, Etymology, Type Locality, and Distribution, by Dennis R. Paulson and Sidney W. Dunkle. Adult flight periods excerpted from “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.

General Characteristics for Cruisers

All cruisers have a single stripe on the lateral sides of their thorax. All cruisers have spots on top of their frons with the notable exception of Royal River Cruiser (Macromia taeniolata), a key field mark for that species.

Genus Didymops

Stream Cruiser

Stream Cruiser (Didymops transversa) is so distinctive in its appearance that no other species of dragonfly looks similar.

Photo credit: Walter Sanford. Stream Cruiser (male).

The following composite image shows two (2) female terminal appendages in the background photo; three (3) male appendages are shown in the inset photo.

Photo credit: Walter Sanford. Stream Cruiser (female).

Genus Macromia

In contrast with genus Didymops, the four species of genus Macromia look similar and can be difficult if not impossible to identify with certainty in the field (especially females of some species).

Accordingly, this identification guide will focus on genus Macromia. Our advice (say it over and over like a mantra): Shoot first (photos, that is) and ask questions later. At a minimum, we recommend photos that show both a dorsal view and lateral view. The more the better! All of that being said, be sure to get at least one “record shot” — get a shot, any shot, and refine the shot as the subject allows.

Photo-illustrated guides for each species in genus Macromia are divided into two sections: one part for males; another part for females. The following field marks can be used to differentiate male versus female dragonflies.

Male: hamules (secondary genitalia located underneath abdominal segments two and three (S2-3); three (3) terminal appendages including two (2) cerci and one (1) epiproct; and “indented” hind wings.

Female: thicker abdomen, no hamules; two (2) cerci; and rounded hind wings.

A three-step process can be used to determine the identity of species in genus Macromia.

  1. Examine the anterior side of the thorax for the presence or absence of prominent frontal stripes, sometimes referred to as antehumeral stripes. This is a key field mark.
  2. Examine the pattern of abdominal bands and spots. Bands on abdominal segments two and seven (S2 and S7) are key field marks. They can appear to be complete or broken dorsally, complete or broken laterally, or can encircle the entire abdominal segment.
  3. Examine the pattern of wing venation, as necessary, specifically the forewing triangle.

Females of Allegheny River Cruiser, Swift River Cruiser (especially the “Illinois” subspecies), and Mountain River Cruiser can be extremely difficult to identify.

Females can be very difficult to distinguish. Source Credit: Paulson, Dennis. Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Location 7243). Princeton University Press. Kindle Edition.

Where the ranges of the two subspecies of Swift River Cruiser overlap (including the eastern Piedmont and Coastal Plain of Virginia) individuals with intermediate characteristics might be encountered. It will be impossible to assign these individuals to either subspecies. (Donnelly and Tennessen 1994).



Prominent frontal stripes are present in two species of genus Macromia: Royal River Cruiser (Macromia taeniolata); and Swift “Georgia” River Cruiser (Macromia illinoiensis georgina).

Royal River Cruiser

Male field marks: No pale spots on top of frons; prominent frontal stripes; no club.

Photo used with written permission from Larry Lynch.

Female field marks: No pale spots on top of frons; prominent frontal stripes; either small paired spots or no spots at the base of abdominal segment eight (S8).

Photo used with written permission from Larry Lynch.

Swift “Georgia” River Cruiser

Male field marks: Pale yellow spots on top of frons; prominent frontal stripes; prominent club.

Photo used with written permission from Joseph Girgente.

Female field marks: Pale yellow spots on top of frons; prominent frontal stripes; prominent yellow crossbar or band at base of abdominal segment eight (S8).

Photo used with written permission from Larry Lynch.



Prominent frontal stripes are absent in three species of genus Macromia: Allegheny River Cruiser (Macromia alleghaniensis); Swift “Illinois” River Cruiser (Macromia illonoiensis illinoiensis); and Mountain River Cruiser (Macromia margarita).

Allegheny River Cruiser

Editor’s Note: Frontal stripes are present in many individuals, but they are generally short and less prominent.

Male field marks: Band on abdominal segment two (S2) slightly broken dorsally, complete laterally; band on abdominal segment seven (S7) completely encircles the abdomen; mesotibial keel length <20%. [See Michael Moore’s excellent annotated images for good illustrations of mesotibial keels.]

Photo credit: Walter Sanford. Specimen collected by Mike Blust.

Photo used with written permission from Larry Lynch.

Female field marks: Band on abdominal segment two (S2) broken dorsally, complete laterally; band on abdominal segment seven (S7) broken laterally.

Photo credit: Mike Boatwright.

Photo credit: Mike Boatwright.

Swift “Illinois” River Cruiser

Male field marks: Band on abdominal segment two (S2) narrow and broken both dorsally and laterally; band on abdominal segment seven (S7) incomplete laterally; generally little or no yellow spots on middle abdominal segments; mesotibial keel length 25-50%.

Editor’s Note: This is the only species of genus Macromia with black auricles.

Photo credit: Mike Boatwright.

Photo used with written permission from Larry Lynch.

Female field marks: Band on abdominal segment two (S2) broken dorsally and laterally; band on abdominal segment seven (S7) broken laterally; spots on dorsum of abdomen generally smaller and more triangular than those of Mountain River Cruiser.

Some females might not be identifiable without in-hand examination of the subgenital plate, tibia length, and wing venation (refer to the section entitled “Wing Venation” toward the end of this guide).

Photo credit: Mike Boatwright.

Mountain River Cruiser

Editor’s Note: Yellow stripe on the face is brighter with a more narrow brown border.

Male field marks: Band on abdominal segment two (S2) broken dorsally, complete laterally; band on abdominal segment seven (S7) incomplete laterally; mesotibial keel length >50%.

Photo credit: Mike Boatwright.

Photo credit: Mike Boatwright.

Female field marks: Band on abdominal segment two (S2) broken dorsally and laterally; band on abdominal segment seven (S7) broken laterally; spots on dorsum of abdomen fairly large and squarish.

Photo credit: Mike Boatwright.

Photo credit: Mike Boatwright.



Wing venation

Wing venation can be used sometimes in conjunction with other characteristics to help distinguish some species of Macromia (river cruisers). However, there is variability within species. In addition, some individuals may exhibit different venation in each wing. Females generally have more crossveins than males. Therefore, one must not rely upon wing venation solely to make a positive identification. The information given here was derived from several scientific sources and represents the most commonly observed venation of both sexes within a species.

Mountain River Cruiser: Forewing triangle usually two-celled and subtriangle usually bordered by three cells; subtriangle one- or two-celled.

Photo credit: Mike Boatwright.

Photo credit: Mike Boatwright.

Allegheny River Cruiser: Forewing triangle usually one-celled and subtriangle usually bordered by two cells; subtriangle usually one-celled.

Photo credit: Mike Boatwright.

Mountain River Cruiser: Forewing triangle 2 celled (90%) and subtriangle bordered by 3 cells (75%); subtriangle 2 celled (55%).

Allegheny River Cruiser: Forewing triangle 1 celled (100%) and subtriangle bordered by 2 cells (100%); subtriangle 1 celled (90%).

Swift “Illinois” River Cruiser: Forewing triangle 1 celled (90%) and subtriangle bordered by 2 cells (70%); subtriangle 1 celled (100%).

Swift “Georgia” River Cruiser: Forewing triangle 2 celled (75%) and subtriangle bordered 2 cells (65%); subtriangle 1 celled (75%).

Royal River Cruiser: Forewing triangle 2 celled (75%) and subtriangle bordered by 3 cells (90%); subtriangle 2 celled (90%).

Editor’s Note: Percentage (%) refers to the percentage of wings showing the venation patterns, among study specimens. (Williamson 1909, and Westfall 1947).



Related Resources

Credits

Thanks to Larry Lynch and Joseph Girgente for permission to use their excellent photographs in this guide.

Also sincere thanks to my good friend Mike Boatwright, without whom it would have been impossible for me to create this guide. Mike is a master at odonate identification based upon key field marks — his descriptors provide the essential framework for the guide. And Mike did most of the heavy lifting by annotating all but two of the images featured in this guide. Excellent work, Mike that I’m honored to be able to share with our fellow odonate enthusiasts.

Copyright © 2022 Walter Sanford. All rights reserved.

Fossil shark tooth, revisited

June 10, 2022

This blog post features a photo of a fossil shark tooth that I collected from the Lee Creek Phosphate Mine in Aurora, North Carolina. I didn’t record the exact date when I collected this specimen, but it was sometime between 1984 and 1989. The mine is currently open for phosphate mining, but it’s closed to the public for fossil collecting.

At the time I collected the tooth, the species of shark was called Carcharodon megalodon. Subsequently, the scientific name was changed to Carcharocles megalodon.

C. megalodon lived in “shallow” seas approximately 10 million years ago. 10 million years seems like a long time on the human time scale, but isn’t long ago on the Geologic Time Scale.

Size and jaw placement

The following annotated image shows one method for measuring the size of a fossil shark tooth. The “slant height” of the tooth is approximately four and one-quarter inches (~4 1/4″) long, as measured along the straighter edge of the tooth (lower edge, relative to the photo).

According to Gareth Williams, a member of the Megalodon Maniacs Facebook group, the tooth is from the upper jaw (lateral).

Lee Creek Phosphate Mine | C. megalodon (lingual side)

Photoblog post flashback

On 11 May 2020 I published a blog post entitled “Focus bracketing using Fujifilm X-T3” that features the same ruler shown in the preceding photo.

The 7″ plastic ruler is from the Calvert Marine Museum. Do you know why the small ruler is 7″ long rather than the more common 6″ length? Please leave a comment if you know the correct answer. Source Credit: Focus bracketing using Fujifilm X-T3.

The reason the ruler is 7″ inches long is because that’s the length of the largest fossil shark teeth ever collected — the holy grail for fossil hunters!

Tech Tips

The Adobe Photoshop “Ruler Tool” can be used to measure the number of pixels between any two points along the ruler shown in the preceding annotated image.

60s ‘shop: Using the ruler tool to measure distances in Photoshop CC, by Photoshop for the Scientist (1:00) provides a clear and concise explanation of how it’s done.

The resulting value (in pixels) can be used to set a custom scale in Photoshop in order to make other measurements of the tooth virtually.

Related Resources

Copyright © 2022 Walter Sanford. All rights reserved.

Fossil shark tooth

June 3, 2022

Sometimes I start working on a blog post by shooting some quick-and-dirty test shots of the subject, such as the following photos of a fossil shark tooth taken using the “Camera” app on my Apple iPad mini 6. Both photos featured in this post are unedited, that is, they are the original JPGs straight from the “Photos” app on the iPad.

Labial side

The first photo was taken with the built-in camera flash turned on. In my opinion, the light is a little too “harsh.”

The photo shows the side of the tooth that faces outward from the mouth of the shark. Notice the tooth edges are serrated.

There are at least two ways to measure the size of a fossil shark tooth. (More about how to measure shark teeth in a follow-up blog post.) This tooth is approximately four and one-quarter inches (~4 1/4″), as measured along the straighter edge of the tooth (right side, relative to the photo).

Lingual side

The last photo was taken was taken using a small LED light and the flash turned off. The LED lighting is better than the flash light, but the specular reflection located near the upper-middle of the tooth enamel is a little distracting.

The photo shows the side of the tooth that faces inward. Three prominent parts of the tooth are easy to identify in the following photo, including the crown/enamel (top), bourlette (middle), and root (bottom).

In the opinion of the author, the lingual side of a shark tooth is often displayed because it is more visually appealing than the labial side.

What’s next?

I plan to shoot better photos, of course, and annotate some of them in order to make it easier to identify the parts of the tooth.

I will describe when and where I collected the fossil shark tooth, identify the species of shark, and provide an estimate of its approximate age on the Geologic Time Scale.

Finally I will explain how to measure the size of a fossil shark tooth, and how to determine whether the tooth is from the upper- or lower jaw, including its approximate position along the jaw line.

Related Resource: Fossil shark tooth, revisited.

Copyright © 2022 Walter Sanford. All rights reserved.

Happy summer!

June 1, 2022

01 June is the first day of summer. What? Perhaps you’re thinking, no that’s incorrect — the first day of summer is on the day of the June Solstice that occurs annually around 21 June. Well, as it turns out both of us are correct.

Atmospheric scientists, including climatologists and meteorologists, define summer as the three-month time period that includes June, July, and August. Astronomers define summer as the three-month time period from the June Solstice to the September Equinox.

Now you know. Again I say, Happy summer!

Related Resource: The Seasons, the Equinox, and the Soltices (by the National Weather Service).

Copyright © 2022 Walter Sanford. All rights reserved.


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