Archive for the ‘dragonflies’ Category

Reasoning for resident Roseate

October 7, 2022

Parts of my last blog post are like the title and abstract for a research paper.

At this point I think it’s reasonable to conclude I was right in 2015 — there is a small, resident, reproducing population of Roseate Skimmer at the park. Source Credit: Breaking news: More Roseate Skimmer spotted at Huntley Meadows Park, by Walter Sanford.

In this blog post, I will provide some of the reasoning that makes my conclusion reasonable.

Probability

First and foremost, ask yourself the obvious question: What are the odds Roseate Skimmer dragonfly (Orthemis ferruginea) migrated to the same park four times during the past eight years? Highly improbable, in my strong opinion.

Adult Flight Period

Long flight season but often most common in fall. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Location 9347). Princeton University Press. Kindle Edition.

Did you notice every sighting of Roseate Skimmer at Huntley Meadows Park, located in Fairfax County, Virginia USA, occurred during the month of September?

  • 10 September 2014 – Walter Sanford (observed only)
  • 23 September 2015 – Walter Sanford (photo)
  • 29 September 2019 – Howard Wu (photo)
  • 15 September 2022 – Lindsay Davis Loyd and Scot Magnotta (photo)

Mike Boatwright, my good friend and an odonate expert, searched the Dragonfly Society of the Americas Odonata Central records database and discovered a similar pattern.

  • The earliest date in South Carolina is July 04 with most records in August to October.
  • All North Carolina records are late August to September.
  • Only two (2) Maryland records in July and August.

Lacking a larger database of sightings that can be used to determine the adult flight period for Roseate Skimmer at Huntley Meadows Park, it appears late-August to September is a good time to look for this rare species.

Why hasn’t the species been spotted more often at HMP?

That’s a good question, with several possible answers.

Roseate Skimmer is a “mudder,” meaning its preferred habitat seems to be ponds where there are mud flats.

Habitat: Very broad habitat tolerance, prefers mud bottoms for larval habitat. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 9354-9355). Princeton University Press. Kindle Edition.

Now ask yourself another question: How many people visit Huntley Meadows Park and spend a lot of time looking carefully at mud flats? I think most people are drawn to the green spaces in the park.

But that’s just part of the problem. Huntley Meadows Park is huge (nearly 1,500 acres) and there are a lot of mud flats throughout the park, including many in places that are mostly inaccessible and/or off-limits to the public. This is especially true during late-summer and early-fall when the water level in the central wetland area tends to be lower than at other times of year.

And it’s almost certainly true that fewer odonate enthusiasts, including me, visit the park as often as they did before the park became overcrowded with photographers who block the boardwalk at prime locations where Roseate Skimmer might be spotted. Fewer odonate hunters searching for relatively few individual specimens at a time of year when there is a lot of suitable habitat is not a formula for success!

First confirmed sighting of a female Roseate Skimmer

The female and male Roseate Skimmer dragonflies that were spotted by Lindsay Davis Loyd and Scot Magnotta are a game-changer. The Roseates were observed perched relatively close to each other. If the pair hadn’t mated already then it’s likely they did — mating is the primary goal of adult odonates. So there are almost certainly Roseate Skimmer eggs in the water at Huntley Meadows Park. If the larvae (nymphs) overwinter successfully, then the beat goes on.

Opposing viewpoints

Equally reasonable opposing viewpoints are invited and welcome.

Until proven otherwise, I will continue to contend there is a resident population of Roseate Skimmer at Huntley Meadows Park.

There are many experienced odonate hunters who live in Northern Virginia. I think it would be great if we could mobilize a group to systematically search the park for Roseate Skimmer next year.

Copyright © 2022 Walter Sanford. All rights reserved.

 

Breaking news: More Roseate Skimmer spotted at Huntley Meadows Park

October 4, 2022

Post Update (as of 03 October 2022)

Lindsay Davis Loyd and Scot Magnotta spotted one adult male and one adult female Roseate Skimmer dragonfly (Orthemis ferruginea) on 15 September 2022 at Huntley Meadows Park. This is the first confirmed sighting of a female Roseate Skimmer at Huntley Meadows Park, Fairfax County, Virginia USA.

At this point I think it’s reasonable to conclude I was right in 2015 — there is a small, resident, reproducing population of Roseate Skimmer at the park.

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.

Jumping spider

March 15, 2022

The following photo shows a tiny spider carcass (~3/16″ long) that was inside an exuvia (~1 3/4” long) from a Common Green Darner dragonfly (Anax junius). The exuvia was collected on 17 June 2021 from a small pond in Prince William County, Virginia USA. I discovered the spider long afterward — too late to save its life.

17 JUN 2021 | PNC. Wm. County, VA | Jumping spider

Thanks to Eva Weiderman and Joseph Girgente — members of the “Odonate Larvae and Exuviae” Facebook group — for their help in identifying the specimen as a jumping spider, Family Saticidae.

Salticidae is one of several families of spiders with eight (8) eyes. My take-away from reading the reference on BugGuide entitled “Spider Eye Arrangements” is identification of this specimen to the genus and species level is challenging at best and impossible at worst.

In contrast, it’s well known that spiders use odonate exuviae for shelter. I wish the jumping spider had come out of its most excellent hidey-hole sooner!

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

Related Resources

Tech Tips

The tiny jumping spider was photographed using a Panasonic Lumix FZ-300, Raynox DCR-250 close-up filter, Godox X2To/p flash trigger, and Godox TT685F plus Altura flash modifier. Camera settings: ISO 100 | f/7.1 | 1/60 s | 56.9mm (316mm, 35mm equivalent).

Raynox DCR-250 close-up filter” is a blog post in which I provide more information about how I use the Raynox with my Panasonic Lumix superzoom bridge cameras.

Copyright © 2022 Walter Sanford. All rights reserved.

Twin-spotted versus Brown Spiketails

February 8, 2022

Four species of genus Cordulegaster are found in the Commonwealth of Virginia: Brown Spiketail (C. bilineata); Tiger Spiketail (C. erronea); Twin-spotted Spiketail (C. maculata); and Arrowhead Spiketail (C. obliqua).

According to the excellent datasets for the Commonwealth of Virginia by Dr. Steve Roble, Staff Zoologist at the Virginia Department of Conservation and Recreation, Division of Natural Heritage, the adult flight periods for spiketail dragonflies are as follows.

MAR 16 – JUL 10 = Twin-spotted

MAR 28 – AUG 08 = Brown

MAY 11 – JUL 17 = Arrowhead

MAY 28 – AUG 22 = Tiger

As you can see, there’s a lot of overlap between the flight periods for Twin-spotted Spiketail and Brown Spiketail. Also notice the overlap between the flight periods for Arrowhead Spiketail and Tiger Spiketail.

I think we can agree the distinctive arrowhead-shaped yellow markings on the abdomen of Arrowhead Spiketail (shown below) are unmistakeable for any other species of spiketail, including Tiger Spiketail.

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

In the opinion of the author it’s more likely a dark-colored Brown Spiketail, such as the one shown below, might be misidentified as a Twin-spotted Spiketail.

02 MAY 2019 | Fairfax County, VA | Brown Spiketail (male)

Differentiating Twin-spotted versus Brown

Twin-spotted and Brown Spiketail dragonflies can be differentiated by looking closely at the yellow markings on abdominal segments one through three (S1-S3).

07 MAY 2018 | Fairfax County, VA | Twin-spotted Spiketail (male)

The pattern of yellow markings on S1-S3 is simpler for Twin-spotted than Brown, as you can see by looking at the full-size versions of these two photos, shown above and below.

11 MAY 2018 | Fairfax County, VA | Brown Spiketail (male)

Female Twin-spotted versus Brown

Female Twin-spotted Spiketails, such as the one shown below, have a much longer subgenital plate (ovipositor) than female Brown Spiketails.

Photo used with written permission from Mike Boatwright.

The subgenital plate for the following female Brown Spiketail is barely visible.

09 MAY 2013 | Fairfax County, VA | Brown Spiketail (female)

It isn’t a lot easier to see the subgenital plate in a close-up view of the same individual shown above.

09 MAY 2013 | Fairfax County, VA | Brown Spiketail (female)

Coach’s Corner

Thanks to Mike Boatwright, founder and administrator of the Virginia Odonata Facebook group, for coaching me up on how to differentiate Twin-spotted Spiketail from Brown Spiketail, including both males and females.

Look for yellow markings on the side of abdominal segments one through three (S1-S3): green arrows show the lack of yellow markings on S1-S3 for Twin-spotted; red arrows show yellow markings on the sides of S1-S3 for Brown.

Set 1

Twin-spotted Spiketail | male (dorsal view)

Photo used with written permission from Mike Boatwright.

Brown Spiketail | male (dorsal view)

Photo used with written permission from Mike Boatwright.

Set 2

Twin-spotted Spiketail | male (dorso-lateral view)

Photo used with written permission from Mike Boatwright.

Brown Spiketail | male (dorso-lateral view)

Photo used with written permission from Mike Boatwright.

What are the take-aways?

Remember the odonate hunter’s credo: Shoot first (photographs, that is); ask questions later. (Repeat it like a mantra.) Get a shot, any shot; refine the shot gradually.

Please don’t waste precious time in the field! You can study the photos when you return home in order to identify the subject(s) you shot as either Twin-spotted Spiketail or Brown Spiketail.

Copyright © 2022 Walter Sanford. All rights reserved.

Twin-spotted Spiketail (terminal appendages)

January 25, 2022

Male

All 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”).

Male members of the Family Cordulegastridae (Spiketails), including male Twin-spotted Spiketail dragonflies (Cordulegaster maculata), have relatively small cerci (terminal appendages) that can be mistaken for female cerci.

07 MAY 2018 | Fairfax County, VA | Twin-spotted Spiketail (male)

Male dragonfly secondary genitalia, called hamules, are located below abdominal segments two and three (S2 and S3), as shown in the following annotated image. Hamules come in a variety of sizes and shapes, but their function is identical for all species of odonates.

07 MAY 2018 | Fairfax County, VA | Twin-spotted Spiketail (male)

Female

As far as I know I have never seen a female Twin-Spotted Spiketail. (I have seen several individuals that I was unable to photograph.) No problem. Mike Boatwright kindly allowed me to annotate a couple of his photographs.

Photo used with written permission from Mike Boatwright.

These individuals are female, as indicated by their rounded hind wings, terminal appendages, and prominent subgenital plate (ovipositor) at the tip of their abdomen.

Photo used with written permission from Mike Boatwright.

Copyright © 2022 Walter Sanford. All rights reserved.


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