Archive for the ‘natural science’ Category

“Odonate Larvae and Exuviae” Facebook group

November 29, 2019

I created a new Facebook group called “Odonate Larvae and Exuviae.” Readers of this blog who enjoy my photographs of odonate exuviae might be interested in following the new group. Please join us!

Copyright © 2019 Walter Sanford. All rights reserved.

Autumn Meadowhawk is a fall species

November 11, 2019

Autumn Meadowhawk (Sympetrum vicinum) is classified as a fall species of odonate. This blog post features two of many Autumn Meadowhawks that were spotted during a photowalk along the boardwalk in the central wetland area at Huntley Meadows Park, Fairfax County, Virginia USA.

The first individual is a male, as indicated by his terminal appendages. He is perched on a Swamp Rose (Rosa palustris) leaf. Nothing says “fall” like this little red devil against a background of fiery foliage!

The last individual is a male, perched on a cattail (Typha sp.) leaf near Swamp Rose and buttonbush (Cephalanthus sp.). The brown globes are the fruit of buttonbush.

The Backstory

My collection of field notes includes two text files that list lots of photos of both Blue-faced Meadowhawk (S. ambiguum) and Autumn Meadowhawk dragonflies that were never published in my photoblog.

Copyright © 2019 Walter Sanford. All rights reserved.

Blue-faced Meadowhawk (young male)

November 8, 2019

A Blue-faced Meadowhawk dragonfly (Sympetrum ambiguum) was spotted near a vernal pool in the forest at Huntley Meadows Park, Fairfax County, Virginia USA.

This individual is a young male, as indicated by the red pruinescence that partially covers his yellow-orange and black abdomen, plus his terminal appendages.

20 SEP 2013 | HMP | Blue-faced Meadowhawk (young male)

Regular readers of my photoblog know I’m fond of head-tilts in which the dragonfly seems to display some of its personality, especially when the individual is looking at me (below).

20 SEP 2013 | HMP | Blue-faced Meadowhawk (young male)

Left, right, left. I followed this guy from perch to perch for several minutes.

20 SEP 2013 | HMP | Blue-faced Meadowhawk (young male)

The Backstory

My collection of field notes includes two text files that list lots of photos of both Blue-faced Meadowhawk and Autumn Meadowhawk dragonflies (S. vicinum) that were never published in my photoblog. Most of the photos were taken during Fall 2013 when one of many vernal pools at Huntley Meadows Park was near peak diversity for odonate species that inhabited the pool. Sadly, those days are long gone!

Copyright © 2019 Walter Sanford. All rights reserved.

Another unknown species of odonate exuvia

November 4, 2019

Another odonate exuvia was collected by Michael Powell during a photowalk with me on 01 June 2019 at Occoquan Regional Park, Fairfax County, Virginia USA. The genus and species is unknown.

Occoquan Regional Park | unknown species | exuvia (face-head)

This specimen might be a member of Family Libellulidae (Skimmers), as indicated by its labium (face mask) and pointy eyes.

Although this exuvia looks similar to the other one that Mike collected on 01 June 2019, it’s smaller and probably not another Slaty Skimmer (L. incesta) exuvia. Many species of skimmers are habitat generalists; the small pond where both exuviae were found is a perfect spot for many members of this family.

The photo (shown above) is a one-off, not a composite image. I plan to create higher quality composite images of this exuvia, shown from all viewpoints including dorsal, ventral, and lateral views. The composite images and one or more dichotomous keys will be used to attempt to identify the genus/species of the specimen.

Related Resource: Vimeo video: Identifying dragonfly larva to family (8:06).

Tech Tips

The following equipment was used to shoot the quick-and-dirty macro photograph featured in this post: Fujifilm X-T1 digital camera; Fujifilm MCEX-11 extension tube; and Fujinon XF80mm macro lens plus lens hood. The camera was set for both manual exposure and manual focus. That’s right, a switch on the camera body is used to set the type of focus. It’s a Fujifilm thing. Camera settings: focal length 80mm (120mm, 35mm equivalent); ISO 200; f/16; 1/180s.

Godox X2TF radio flash trigger, mounted on the hotshoe of my X-T1, was used to control two off-camera external flash units set for radio slave mode: Godox TT685F Thinklite TTL Flash (manual mode); and Godox TT685o/p Thinklite Flash for Olympus/Panasonic Cameras (manual mode). Both flash units were fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier.

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

Copyright © 2019 Walter Sanford. All rights reserved.

Detente

October 30, 2019

Two Autumn Meadowhawk dragonflies (Sympetrum vicinum) were spotted perched side-by-side on the boardwalk in the central wetland area at Huntley Meadows Park (HMP), Fairfax County, Virginia USA. Both individuals are males, as indicated by their coloration and terminal appendages.

15 NOV 2013 | HMP | Autumn Meadowhawk (males)

Male dragonflies of the same species are natural rivals, competing for the attention of females that are willing to mate. Like many, if not most other species of dragonflies, male Autumn Meadowhawk dragonflies stake out a “territory” near prime spots for females to lay eggs (oviposition); unlike many, if not most other species, male Autumn Meadowhawks don’t seem to defend their territory aggressively.

15 NOV 2013 | HMP | Autumn Meadowhawk (males)

Notice the male shown on the upper-left is using his front legs like windshield wipers to clean his eyes and face. Hey, he wants to look well-groomed for the ladies!

Related Resources

The Backstory

My collection of field notes includes two text files that list lots of photos of both Blue-faced Meadowhawk and Autumn Meadowhawk dragonflies (S. vicinum) that were never published in my photoblog. Most of the photos were taken during Fall 2013 when one of many vernal pools at Huntley Meadows Park was near peak diversity for odonate species that inhabited the pool. Sadly, those days are long gone!

Copyright © 2019 Walter Sanford. All rights reserved.

Data mining for Autumn Meadowhawk

October 28, 2019

This is a follow-on to my last blog post, Are adult Autumn Meadowhawks arboreal?

Data mining can be used to recognize patterns in official records of field observations by many amateur and professional odonate hunters, confirmed by experienced vetters.

Let’s begin by looking at the adult flight period for Autumn Meadowhawk (Sympetrum vicinum), the target species for a proposed field study during 2020 at the Vermont Institute of Natural Science.

Adult Flight Period

According to records for the Commonwealth of Virginia maintained by Dr. Steve Roble, Staff Zoologist at the Virginia Department of Conservation and Recreation, Division of Natural Heritage, the adult flight period for Autumn Meadowhawk (S. vicinum) is from May 28 to January 03. The species is classified as “common.” Its habitat is “ponds.”

Bear in mind, Dr. Roble’s records are for the entire state, therefore the adult flight period for S. vicinum seems to be longer than it is in reality. The adult flight period for a single site is probably shorter. For example, according to records for Northern Virginia maintained by Kevin Munroe, former manager of Huntley Meadows Park, the adult flight period for Autumn Meadowhawk is June 13 to December 10 (seen most September to October).

DSA Odonata Central Records

What is shown by a deep-dive into the Dragonfly Society of the Americas Odonata Central records database for Autumn Meadowhawk in the Commonwealth of Virginia?

There are currently 38 confirmed records for S. vicinum in Virginia, as shown by the following distribution map.

Source Credit: Abbott, J.C. 2006-2019. OdonataCentral: An online resource for the distribution and identification of Odonata. Available at http://www.odonatacentral.org. (Accessed: October 27, 2019).

Key: blue dots = Dot Map Project; green dots = Accepted records; yellow dots = Pending records.

Analysis

There are 14 records for teneral/immature adult Autumn Meadowhawk, ranging from 30 May to 19 August: May (1); June (5); July (5); August (3). Notice that the greatest cluster of records for teneral/immature adults occurs in June and July. There are a few records for mature adults toward the end of this time period and no records for mating pairs.

There are 24 records for mature adult Autumn Meadowhawk, ranging from 07 August to 03 January: August (2); September (5); October (13); November (1); December (2); January (1). Only a few records for teneral/immature adults occur at the beginning of this time period. The greatest cluster of records for mature adults occurs in October. Seven (7) of the records throughout the time period are for mating pairs, beginning in September; the greatest cluster of records for mating pairs also occurs in October.

What are the take-aways?

38 records is an admittedly small sample size. In the opinion of the author, patterns in the data are muddied by analyzing data for the entire state rather than a single location. There is almost certainly a south-to-north pattern in dates of emergence, mating, and disappearance for any given species, as well as atypical patterns resulting from micro-climates that exist throughout the state.

All of that being said, the data in the DSA Odonata Central records database for Virginia is consistent with my first-hand observations in Northern Virginia showing that Autumn Meadowhawk emerges in mid- to late-June, disappears for two- to three months, and returns to the ground/water when it’s time to mate during fall.

One big question remains to be answered: Where do adult Autumn Meadowhawks go when they disappear soon after emergence — do they live in the forest canopy? One thing we know is certain: There are few if any official records for mature adult Autumn Meadowhawk on the ground during mid- to late-summer. Food for thought.

Related Resource: Are adult Autumn Meadowhawks arboreal?

Copyright © 2019 Walter Sanford. All rights reserved.

Are adult Autumn Meadowhawks arboreal?

October 25, 2019

Autumn Meadowhawk (Sympetrum vicinum) is classified as a fall species of odonate. In the mid-Atlantic United States, meadowhawks seem to disappear for several months after they emerge during early to mid-summer and reappear during fall. Where do they go? No one knows for sure. I speculate Autumn Meadowhawk is an arboreal species of dragonfly that returns to the ground/water when it’s time to mate.

Emergence

The first individual — photographed soon after emergence — is a/an teneral/immature male, as indicated by the tenuous appearance of his wings, coloration, and terminal appendages.

24 JUN 2016 | HMP | Autumn Meadowhawk (teneral/immature male)

The next individual is a/an teneral/immature female, as indicated by the tenuous appearance of her wings, coloration, and terminal appendages.

24 JUN 2016 | HMP | Autumn Meadowhawk (teneral/immature female)

Time to mate

Fall is the time to mate for mature adult Autumn Meadowhawk dragonflies (S. vicinum), as you can see in the following photo.

15 NOV 2013 | HMP | Autumn Meadowhawk (mating pair, “in wheel”)

This mating pair is “in wheel”: the male is on the upper-left; the female is on the lower-right. All dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back: male dragonfly secondary genitalia, called hamules, are located in segments two and three (S2 and S3); female genitalia in segment eight (S8). Dragonflies form the mating wheel in order for their genitalia to connect during copulation.

Forest Canopy Walk at Vermont Institute of Natural Science

Observing dragonflies at the Earth’s surface is fairly easy; observing dragonflies at the treetops, not so much. The new Forest Canopy Walk at the Vermont Institute of Natural Science (VINS) should facilitate the latter.

During 2020, I hope to collaborate with Kelly Stettner, Black River Action Team (BRAT), and Anna Morris, Lead Environmental Educator, VINS, to gather evidence that supports my speculation that adult meadowhawk dragonflies are arboreal. Field observations will be collected on the ground and along the Forest Canopy Walk.

Hosted by Anna Morris, Kelly Stettner and her family scouted the VINS site on 05 October 2019, including the new Forest Canopy Walk and nearby water bodies that provide suitable habitat for Autumn Meadowhawk. Special thanks to Anna for providing a behind the scenes tour a week before the official opening of the Forest Canopy Walk.

Gallery photos used with permission from Kelly Stettner, BRAT.

A week later, Autumn Meadowhawk was observed along the Forest Canopy Walk for the first time. The following photos provide circumstantial evidence that we might be on the right track. I love it when a plan comes together!

Gallery photos used with permission from Anna Morris, VINS.

I’m happy to share that during our public Forest Canopy Walk opening today [12 October 2019], I was stationed at the Eagle platform and got to see two (2) meadowhawks zooming around, then perched on the railing (pictures attached)! This is about 60 feet up, near a Sugar Maple and a Red Oak. [More meadowhawks were seen] the next day at nearly 90 feet up! At this height and as it was so sunny there were at least four individuals zooming around, landing on visitors, etc. Source Credit: Anna Morris, Lead Environmental Educator, VINS.

Related Resources

Copyright © 2019 Walter Sanford. All rights reserved.

Building a case for Slaty Skimmer

October 23, 2019

With each new photo set of this unknown species of odonate exuvia, a case is building slowly for Slaty Skimmer (Libellula incesta).

Occoquan Regional Park | unknown species | exuvia (lateral)

A piece of white schmutz was removed from the tip of the abdomen, enabling a clearer view of abdominal segment nine (S9). Look closely at the two photos featured in this post. Notice there are stubby mid-dorsal hooks (not cultriform) on abdominal segments four through eight (S4-S8).

Occoquan Regional Park | unknown species | exuvia (dorsal)

The last photo shows a closer view of the anal pyramid. Notice the lateral caudal appendages (cerci) are less than half as long as the inferior appendages (paraprocts).

Soltesz, p. 43 – Key to the Species of the Genus Libellula

Field marks that match this specimen are highlighted in boldface green text.

1b. Dorsal hooks regularly present on segments 4 to 8. [2]
2b. Palpal setae 5 (sometimes 6 in cyanea). [5]
5a. Epiproct distinctly decurved at tip. [6]
6b. Length of last instar about 26mm; cerci less than half as long as paraprocts. [incesta]

Punch List

I need to look at the inside of the labium (face mask) in order to count palpal setae. The epiproct must be cleaned to see whether it is decurved. This exuvia was deformed as a result of emergence, so it’s impossible to make an accurate measurement of the length of the specimen. That said, the exuvia is more than 22.0 mm (0.9 in) long. (22 mm is the length of the last instar for L. cyanea.)

And of course, I need to annotate all of the images in this series of blog posts in order to illustrate the unfamiliar vocabulary that is used in virtually all dichotomous identification keys.

Related Resources

Tech Tips

The following equipment was used to shoot the quick-and-dirty macro photographs featured in this post: Fujifilm X-T1 digital camera; Fujifilm MCEX-16 extension tube; and Fujinon XF80mm macro lens plus lens hood. The camera was set for both manual exposure and manual focus. That’s right, a switch on the camera body is used to set the type of focus. It’s a Fujifilm thing. Camera settings: focal length 80mm (120mm, 35mm equivalent); ISO 200; f/16; 1/180s.

Godox X2TF radio flash trigger, mounted on the hotshoe of my X-T1, was used to control two off-camera external flash units set for radio slave mode: Godox TT685F Thinklite TTL Flash (manual mode); and Godox TT685o/p Thinklite Flash for Olympus/Panasonic Cameras (manual mode). Both flash units were fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier.

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

Copyright © 2019 Walter Sanford. All rights reserved.

Unknown species of odonate exuvia (ventral)

October 21, 2019

This post features another photo of an odonate exuvia collected by Michael Powell during a photowalk with me on 01 June 2019 at Occoquan Regional Park, Fairfax County, Virginia USA. The photo is a one-off (not a composite image) showing the ventral view of the exuvia.

The genus and species is unknown. This specimen might be a member of Family Libellulidae (Skimmers), probably Slaty Skimmer (Libellula incesta).

Occoquan Regional Park | unknown species | exuvia (ventral)

Related Resource: Vimeo video: Identifying dragonfly larva to family (8:06).

Tech Tips

The following equipment was used to shoot the quick-and-dirty macro photograph featured in this post: Fujifilm X-T1 digital camera; Fujifilm MCEX-16 extension tube; and Fujinon XF80mm macro lens plus lens hood. The camera was set for both manual exposure and manual focus. That’s right, a switch on the camera body is used to set the type of focus. It’s a Fujifilm thing. Camera settings: focal length 80mm (120mm, 35mm equivalent); ISO 200; f/16; 1/180s.

Godox X2TF radio flash trigger, mounted on the hotshoe of my X-T1, was used to control two off-camera external flash units set for radio slave mode: Godox TT685F Thinklite TTL Flash (manual mode); and Godox TT685o/p Thinklite Flash for Olympus/Panasonic Cameras (manual mode). Both flash units were fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier.

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

Copyright © 2019 Walter Sanford. All rights reserved.

Unknown species of odonate exuvia, revisited

October 18, 2019

This post features more photos of an odonate exuvia collected by Michael Powell during a photowalk with me on 01 June 2019 at Occoquan Regional Park, Fairfax County, Virginia USA. Both photos are one-offs, not composite images.

The genus and species is unknown. This specimen might be a member of Family Libellulidae (Skimmers).

Occoquan Regional Park | unknown species | exuvia (lateral)

Mid-dorsal hooks are present on some abdominal segments. Lateral spines are located on abdominal segments eight and nine (S8-9).

Occoquan Regional Park | unknown species | exuvia (dorsal)

I still need to take close-up photos of the anal pyramid and shoot photos of the ventral view before I attempt to identify the genus/species of the specimen using one or more dichotomous keys.

Related Resource: Vimeo video: Identifying dragonfly larva to family (8:06).

Tech Tips

The following equipment was used to shoot the quick-and-dirty macro photograph featured in this post: Fujifilm X-T1 digital camera; Fujifilm MCEX-16 extension tube; and Fujinon XF80mm macro lens plus lens hood. The camera was set for both manual exposure and manual focus. That’s right, a switch on the camera body is used to set the type of focus. It’s a Fujifilm thing. Camera settings: focal length 80mm (120mm, 35mm equivalent); ISO 200; f/16; 1/180s.

Godox X2TF radio flash trigger, mounted on the hotshoe of my X-T1, was used to control two off-camera external flash units set for radio slave mode: Godox TT685F Thinklite TTL Flash (manual mode); and Godox TT685o/p Thinklite Flash for Olympus/Panasonic Cameras (manual mode). Both flash units were fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier.

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

Copyright © 2019 Walter Sanford. All rights reserved.


%d bloggers like this: