Posts Tagged ‘Stream Cruiser dragonfly’

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.

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.

Beware of look-alikes!

September 28, 2021

Some species of dragonfly larvae/exuviae look similar to other species. Here are a couple of look-alikes from two different families that might fool you.

One species of Corduliidae in our region [North America], Epitheca princeps, resembles the macromiid general body shape and is nearly as large, but the legs are short compared to its body dimensions and it lacks a triangular frontal projection. Source Credit: K. J. Tennessen, Dragonfly Nymphs of North America, https://doi.org/10.1007/978-3-319-97776-8_10, Macromiidae, p. 329.

The first annotated image shows a ventral view of a Prince Baskettail (Epitheca princeps) exuvia. E. princeps is a member of Family Corduliidae (Emeralds).

Notice the appearance of the E. princeps exuvia is quite similar to the Stream Cruiser (Didymops transversa) exuvia shown below. D. transversa is a member of Family Macromiidae (Cruisers).

The E. princeps exuvia features lateral spines and well-developed mid-dorsal hooks on some abdominal segments. Notably “it lacks a triangular frontal projection” (K. J. Tennessen), or stated more simply, there isn’t a “horn” on its face-head.

The D. transversa exuvia also features lateral spines and mid-dorsal hooks, as shown below. Notice the mid-dorsal hooks aren’t as cultriform as E. princeps. In contrast to the E. princeps exuvia, notice the prominent “horn” on the face of the D. transversa exuvia. It’s all about the “horn.”

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

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.

Stream Cruiser dragonfly (female)

May 18, 2021

A Stream Cruiser dragonfly (Didymops transversa) was spotted during a recent photowalk with Michael Powell along a mid-size stream at an undisclosed location in Prince William County, Virginia USA.

This individual is a female, as indicated by her thick abdomen and terminal appendages.

13 MAY 2021 | Prince William County, VA | Stream Cruiser (female)

The female was perched in a large field near the same location where Mike Powell found a Stream Cruiser exuvia on 13 April 2021.

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Exuvia from Family Macromiidae (Cruisers)

May 14, 2021

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

This cast skin is definitely from a member of Family Macromiidae (Cruisers), as indicated by its long legs and the shape of its body.

13 APR 2021 | Prince William County, VA | Stream Cruiser (exuvia)

Mike’s macro photo of the same subject (shown below) turned out better than mine, taken with a superzoom bridge camera. Look closely at the full-size version of Mike’s photo. Nothing says Family Macromiidae (Cruisers) like the “horn” on the front of the face/head of the exuvia!

Photo used with written permission from Michael Powell.

The following excerpt from Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz, shows the couplet that I think indicates this specimen is from a Stream Cruiser dragonfly (Didymops transversa).

The adult flight periods for the three species of cruisers found in Northern Virginia provide circumstantial evidence in support of my tentative identification. Source Credit: “Dragonflies of Northern Virginia” Web site by Kevin Munroe.

What’s next?

The specimen was collected in order to shoot a complete set of macro photographs of the exuvia in my home “studio.”

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Epitheca princeps exuvia

September 6, 2018

An odonate exuvia was collected by Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, on 07 June 2018 at Otter Lake in Amherst County, Virginia USA.

A two-step process was used to identify the genus and species of the specimen.

  1. Determine the family.
  2. Determine the genus and species.

Step 1. Family

First, determine the family of the specimen. For reference, watch the excellent Vimeo video, Identifying dragonfly larva to family (8:06). Here’s the decision tree used to identify the exuvia as a member of the Family Corduliidae (Emeralds).

  • The specimen has a mask-like labium (prementum) that covers the face, as shown in Image No. 1, characteristic of four families of odonates: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).
  • There is no horn on the face-head, characteristic of Macromiidae, so it’s not a cruiser.
  • Cordulegastridae has jagged crenulations on its labium, so it’s not a spiketail. The crenulations for Corduliidae and Libellulidae look similar.
  • Look at the anal pyramid to differentiate Corduliidae and Libellulidae: It’s probably Corduliidae if the cerci are at least half as long as the paraprocts, as shown in Image No. 4. [Editor’s Note: It’s probably Libellulidae if the cerci are less than half the length of the paraprocts.]

In summary, the exuvia has a mask-like labium with relatively smooth crenulations, no horn on its face-head, and the cerci are more than half as long as the paraprocts, confirming that the specimen is a member of Family Corduliidae (Emeralds).

No. 1Epitheca princeps | exuvia (face-head)

Step 2. Genus and species

Characters from two dichotomous keys were used to identify the genus and species: Prince Baskettail dragonfly (Epitheca princeps). See Epitheca princeps exuvia, another of my illustrated guides to identification of odonate exuviae, for a detailed explanation of the decision tree used to identify the genus and species of this specimen.

No. 2 | Epitheca princeps | exuvia (dorsal)

This individual is a male, as indicated by the vestigial hamuli visible on the ventral side of abdominal segments two and three (S2-3).

No. 3Epitheca princeps | exuvia (ventral)

Notice the cerci are at least half as long as the paraprocts, as shown in Image No. 4.

No. 4Epitheca princeps | exuvia (posterior abdomen)

Image No. 5 shows a dorsal-lateral view of the mid-dorsal hooks.

No. 5Epitheca princeps | exuvia (dorsal-lateral)

Look-alike species

I really wanted this specimen to be Stream Cruiser dragonfly (Didymops transversa). I think exuviae from D. transversa and E. princeps are similar in appearance — an opinion not shared by at least one expert on identification of odonate exuviae.

Two characters proved to be the deal-breaker that forced me to abandon D. tranversa in favor of E. princeps. 1) The specimen does not have a horn on its face-head. 2) This specimen is only 25 mm long (2.5 cm); D. transversa larvae/exuviae are 30 mm long (3.0 cm), according to Dragonflies of North America, Needham, James G., et al.

Related Resources

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 Image No. 1-5: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode.

Image No. 1-5 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017: Image No. 1 (7 photos); Image No. 2 (22 photos); Image No. 3 (19 photos); Image No. 4 (10 photos); Image No. 5 (20 photos).

Copyright © 2018 Walter Sanford. All rights reserved.

Green-eyed Stream Cruiser

May 12, 2017

Stream Cruiser dragonfly (Didymops transversa) was spotted during a photowalk along a mid-size stream in Fairfax County, Virginia USA. This individual is a male, as indicated by his terminal appendages and indented hind wings.

03 MAY 2017 | Fairfax County, VA | Stream Cruiser (male)

Male: Eyes brown with green highlight above. … Female: Eyes brown. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 7192, 7194-7195). Princeton University Press. Kindle Edition.

I’ve never seen a green-eyed Stream Cruiser like this one — every one had brown eyes, including both males and females.

Copyright © 2017 Walter Sanford. All rights reserved.

Stream Cruiser dragonfly (male)

April 14, 2017

Another Stream Cruiser dragonfly (Didymops transversa) was spotted during a photowalk along Beaver Pond Loop Trail at Accotink Bay Wildlife Refuge, Fairfax County, Virginia USA.

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

Stream Cruiser dragonflies typically perch at a 45° angle because of their extremely long legs, especially noticeable in the last photo.

For another perspective on the same male, both literally and figuratively, see Stream Cruiser dragonfly by fellow photoblogger Michael Powell.

Copyright © 2017 Walter Sanford. All rights reserved.


%d bloggers like this: