Posts Tagged ‘Family Libellulidae (Skimmers)’

Relative length of cerci versus paraprocts

October 19, 2021

A quote from my last blog post sets the stage for this post …

One way to differentiate Emerald from Skimmer larvae/exuvia is to examine the anal pyramid: it’s probably Corduliidae (Emeralds) if the cerci are at least half as long as the paraprocts; it’s probably Libellulidae (Skimmers) if the cerci are less than half the length of the paraprocts. More about this in a follow-up blog post. Source Credit: Ventromedial groove, by Walter Sanford.

Here are two examples that illustrate when the method works to confirm exuviae are from Family Libellulidae (Skimmers).

Eastern Amberwing (Perithemis tenera)

Look closely at the full-size version of the following annotated image of an exuvia from an Eastern Amberwing dragonfly (Perithemis tenera).

Notice the cerci are slightly less than half the length of the paraprocts, indicating this specimen is from Family Libellulidae (Skimmers).

Carolina Saddlebags (Tramea carolina)

The next specimen is an exuvia from a Carolina Saddlebags dragonfly (Tramea carolina).

Notice the cerci are slightly less than half the length of the paraprocts, indicating this specimen also is from Family Libellulidae (Skimmers).


Finally, here’s an example that illustrates when the method doesn’t work.

Spot-winged Glider (Pantala hymenaea)

The last specimen is an exuvia from a Spot-winged Glider dragonfly (Pantala hymenaea). Spot-winged Glider is a member of Family Libellulidae (Skimmers).

Notice the cerci are longer than half the length of the paraprocts, suggesting this specimen is from Family Corduliidae (Emeralds). But the exuvia isn’t an Emerald — it’s a Skimmer!

As it turns out, for genus Pantala it’s more important to look at the relative length of the superior abdominal appendage (epiproct) versus the inferior abdominal appendages (paraprocts). Who knew?

What the take-aways?

Although I haven’t identified (with certainty) many species of exuviae from Family Libellulidae (Skimmers), it didn’t take long to find an exception to the rule of thumb for differentiating Emeralds and Skimmers by examining the relative length of cerci versus paraprocts.

In contrast, the rule of thumb that looks at the presence or absence of a ventromedial groove seems to work every time, with the caveat that some species in other families feature a ventromedial groove. In those cases, the family to which the specimen belongs is fairly obvious.

I think it’s good to have more than one arrow in your quiver, so you should be familiar with both methods for differentiating Emeralds and Skimmers. That said, I recommend starting the process of identification by looking for a ventromedial groove.

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Ventromedial groove

October 15, 2021

In North America (restricted to Canada and the United States of America) there are seven families of dragonflies in the suborder Anisoptera.

Identification of dragonfly larvae (nymphs)/exuviae to the Family Level is fairly straightforward for five of the seven families.

Flat labium

Three families feature a flat labium and are easy to differentiate: Aeshnidae (Darners); Gomphidae (Clubtails); and Petaluridae (Petaltails).

Darner larvae (nymphs)/exuviae have long, thin antennae; Clubtail larvae/exuviae have short, thick antennae. Petaltail larvae/exuviae feature several distinctive field marks that are easy to recognize.

Mask-like labium

Four families feature a mask-like labium: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).

Two of these four families are easy to recognize. The distinctive jagged crenulations on the face mask of Spiketails are unmistakeable! Cruisers feature a prominent “horn” on the face-head.

In the opinion of the author, larvae/exuviae from Emeralds and Skimmers can be challenging to differentiate and identify to the family level.

Anal pyramid

One way to differentiate Emerald from Skimmer larvae/exuvia is to examine the anal pyramid: it’s probably Corduliidae (Emeralds) if the cerci are at least half as long as the paraprocts; it’s probably Libellulidae (Skimmers) if the cerci are less than half the length of the paraprocts. More about this in a follow-up blog post.

Ventromedial groove

Another way to differentiate Emerald from Skimmer larvae/exuvia is to look for a “ventromedial groove” in the prementum: it’s probably Corduliidae (Emeralds) if there is a ventromedial groove; it’s probably Libellulidae if there isn’t.

For example, look at the full-size version of the following annotated image of a Common Baskettail dragonfly (Epitheca cynosura) exuvia. Notice the groove down the middle of the prementum, oriented vertically in the photo — that’s a “ventromedial groove” (a compound word derived from “ventral” and “medial/midline”) — indicating this specimen probably is from Family Corduliidae (Emeralds).

… the groove is developed on the basal half of the prementum … Source Credit: K. J. Tennessen, Dragonfly Nymphs of North America, https://doi.org/10.1007/978-3-319-97776-8_11, p. 346.

Here’s another example showing a ventromedial groove in the prementum of a Prince Baskettail dragonfly (Epitheca princeps) exuvia.

In contrast, look closely at the full-size version of the following photo of a Spot-winged Glider dragonfly (Pantala hymenaea) exuvia. Notice there is no ventromedial groove in the prementum, indicating this specimen probably is from Family Libellulidae (Skimmers).

An important caveat

Beware: Some larvae/exuviae in other families of dragonflies, such as Tiger Spiketail dragonfly (Cordulegaster erronea), feature a ventromedial groove in the prementum. Therefore the take-away from this post is the presence of a ventromedial groove is not a single definitive morphological character for Emeralds, rather it should be used in combination with other field marks.

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Previews of Coming Attractions – Fall Species of Odonates

August 31, 2021

There is an annual cycle of odonate activity that can be subdivided into three broad categories: Early Season (spring); Mid-season (summver); and Late Season (fall).

As we endure the “Dog Days of Summer,” waiting for the calendar to turn to fall, it’s time to begin looking for the Late Season (fall) species of odonates.

This blog post provides a photo sampler of some of the fall species of odonates that can be seen during September, October, and November in the Commonwealth of Virginia. This post is not intended to be a comprehensive field guide that features every odonate species that can be seen during the same time period.

Full Disclosure

Some fall species are easier to find than others. And some species are flyers rather than perchers, making it almost essential to capture them in flight using an insect net. That being said, it’s richly rewarding to find any of the rare to uncommon species so do your homework and be persistent. Good luck and happy hunting!


Editor’s Notes

Click on the date listed in the caption for each photo to see the original blog post for that image; click on the odonate name to see all of my blog posts related to that species.

Sincere thanks to Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, for providing photographs of many of the rare to uncommon fall species of odonates featured in this photo sampler. Click on the word “Photo” in the caption for each of Mike’s photographs to see his original Facebook post for that image.

Every species features the following information: common name; scientific name; early-date/late-date; abundance; and habitat. All information is 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.


Dragonflies (Order Anisoptera)

Family Aeshnidae (Darners)

Black-tipped Darner (Aeshna tuberculifera)

Adult flight period: JUN 30 – OCT 29. Rare to uncommon. Habitat: Montane ponds.

Photo used with written permission from Michael Boatwright.

Common Green Darner (Anax junius)

Adult flight period: FEB 27 – DEC 30. Common. Habitat: Ponds.

Fawn Darner (Boyeria vinosa)

Adult flight period: JUN 03 – NOV 07. Common. Habitat: Streams, rivers.

Shadow Darner (Aeshna umbrosa)

Adult flight period: JUN 08 – DEC 05. Common. Habitat: Ponds, streams.

Family Corduliidae (Emeralds)

Clamp-tipped Emerald (Somatochlora tenebrosa)

Adult flight period: JUN 08 – OCT 15. Common. Habitat: Ponds, small streams.

Photo used with written permission from Michael Boatwright.

Fine-lined Emerald (Somatochlora filosa)

Adult flight period: JUL 10 – OCT 15. Rare to uncommon. Habitat: Boggy streams, swamps, marshes.

18 SEP 2019 | PNC. Wm. County | Fine-lined Emerald (male)

Family Gomphidae (Clubtails)

Arrow Clubtail (Stylurus spiniceps)

Adult flight period: JUN 13 – OCT 19. Uncommon to common. Habitat: Rivers.

Photo used with written permission from Michael Boatwright.

Laura’s Clubtail (Stylurus laurae)

Adult flight period: JUN 20 – SEP 26. Rare to uncommon. Habitat: Streams, rivers.

Photo used with written permission from Michael Boatwright.

Russet-tipped Clubtail (Stylurus plagiatus)

Adult flight period: JUN 15 – NOV 06. Uncommon to common. Habitat: Streams, rivers.

Family Libellulidae (Skimmers)

Autumn Meadowhawk (Sympetrum vicinum)

Adult flight period: MAY 28 – JAN 03. Common. Habitat: Ponds.

Blue-faced Meadowhawk (Sympetrum ambiguum)

Adult flight period: MAY 22 – NOV 19. Uncommon. Habitat: Swamps, ponds.

Black Saddlebags (Tramea lacerata)

Adult flight period: APR 12 – OCT 30. Common. Habitat: Ponds.

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

Spot-winged Glider (Pantala hymenaea)

Adult flight period: MAY 08 – OCT 20. Common. Habitat: Ponds.

A Spot-winged Glider dragonfly (Pantala hymenaea) netted at Saint Louis Catholic School, Fairfax County, Virginia USA. This individual is a female.

20 JUL 2016 | Fairfax County, VA USA | Spot-winged Glider (female)

Wandering Glider (Pantala flavescens)

Adult flight period: MAY 02 – NOV 17. Common. Habitat: Ponds.

Damselflies (Order Zygoptera)

Family Lestidae (Spreadwings)

Great Spreadwing (Archilestes grandis)

Adult flight period: JUN 25 – NOV 11. Uncommon. Habitat: Streams, ponds.

Spotted Spreadwing (Lestes congener)

Adult flight period: JUN 10 – NOV 11. Uncommon. Habitat: Ponds.

Photo used with written permission from Michael Boatwright.

 


Classification of Fall Species into Sub-groups

Migratory Species

At least five major species of dragonflies known to be migratory in North America.

  • Black Saddlebags (Tramea lacerata)
  • Common Green Darner (Anax junius)
  • Spot-winged Glider (Pantala hymenaea)
  • Wandering Glider (Pantala flavescens)

Rare to Uncommon Species

  • Arrow Clubtail (Stylurus spiniceps)
  • Black-tipped Darner (Aeshna tuberculifera)
  • Blue-faced Meadowhawk (Sympetrum ambiguum)
  • Clamp-tipped Emerald (Somatochlora tenebrosa)
  • Fine-lined Emerald (Somatochlora filosa)
  • Laura’s Clubtail (Stylurus laurae)
  • Ocellated Darner (Boyeria grafiana)
  • Great Spreadwing (Archilestes grandis)
  • Spotted Spreadwing (Lestes congener)

Copyright © 2021 Walter Sanford. All rights reserved.

Yellow-sided Skimmer (terminal appendages)

August 24, 2021

Female and male Yellow-sided Skimmer dragonflies (Libellula flavida) were spotted at a small pond at an undisclosed location in Prince William County, Virginia USA.

Female

The first individual is a female, as indicated by her mostly yellow coloration and terminal appendages.

17 JUN 2021 | PNC. Wm. County | Yellow-sided Skimmer (female)

Female dragonflies have a pair of cerci (superior appendages) that have little or no function.

Mature male

The last individual is a mature male, as indicated by his light-blue pruinescence and terminal appendages.

17 JUN 2021 | PNC. Wm. County | Yellow-sided Skimmer (male)

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”).

Immature male Yellow-sided Skimmers look similar to females of the same species. Terminal appendages can be used to differentiate the sex of immature males and mature females.

Related Resource: Yellow-sided Skimmer (male and female) – a blog post by Walter Sanford.

Copyright © 2021 Walter Sanford. All rights reserved.

More Bar-winged Skimmers (males)

July 23, 2021

At least two male Bar-winged Skimmer dragonflies (Libellula axilena) were spotted along the shoreline of a small pond at an undisclosed location in Prince William County, Virginia USA.

It’s possible all of the photos featured in this blog post are of the same mature male that is featured in another recent post, as indicated by a distinctive pattern of spider web strands on the wings of the dragonfly.

Look closely along the leading edge of the wings. Notice the dark bars from which the common name for this species is derived are almost invisible.

17 JUN 2021 | PNC. Wm. County |  Bar-winged Skimmer (mature male)

17 JUN 2021 | PNC. Wm. County |  Bar-winged Skimmer (mature male)

17 JUN 2021 | PNC. Wm. County |  Bar-winged Skimmer (mature male)

17 JUN 2021 | PNC. Wm. County |  Bar-winged Skimmer (mature male)

For what it’s worth, the first and last photos in this set are my favorite.

Related Resource: Bar-winged Skimmer dragonfly (male).

Copyright © 2021 Walter Sanford. All rights reserved.

Bar-winged Skimmer dragonfly (male)

July 9, 2021

A Bar-winged Skimmer dragonfly (Libellula axilena) was spotted along the shoreline of a small pond at an undisclosed location in Prince William County, Virginia USA.

This individual is a mature male, as indicated by his coloration and terminal appendages.

17 JUN 2021 | PNC. Wm. County |  Bar-winged Skimmer (mature male)

This mature male has mated many times, as indicated by the scratches on the light-blue pruinescence covering his abdomen.

Males that have mated often have marks on their abdomen where the female legs have scratched them. This is especially obvious in species in which males develop pruinosity, as the pruinosity on the mid-abdomen is scratched off, and the signs are visible at some distance. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 390-392). Princeton University Press. Kindle Edition.

The next photo is full-frame (4,000 x 3,000 pixels), that is, uncropped.

17 JUN 2021 | PNC. Wm. County |  Bar-winged Skimmer (mature male)

Look closely along the leading edge of this individual’s wings. Notice the dark bars from which the common name for this species is derived are almost invisible.

Habitat

According to Dr. Steve Roble’s excellent datasets for the Commonwealth of Virginia, the adult flight period for Bar-winged Skimmer is from May 08 to September 28. Dr. Roble describes its habitat as “ponds.”

“Ponds” is perhaps too simple a descriptor for the habitat preferred by Bar-winged Skimmer, otherwise L. axilena should be more common than a map of its range suggests. Dennis Paulson provides a little more specificity.

Habitat: Wooded slow streams and sloughs, forest pools. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Location 9152). Princeton University Press. Kindle Edition.

Kevin Munroe, former manager at Huntley Meadows Park, provides the best description of Bar-winged Skimmer habitat that I’ve seen.

One of our less common skimmers, this dragonfly has relatively specific habitat needs. It prefers very shallow marshy pools in the full sun. If there’s enough water for fish, it’s too deep for Bar-winged Skimmers. And of course shallow pools in the full sun tend to quickly evaporate and dry up, so stable populations in Northern Va. are few and far between. The similar Great Blue Skimmer also likes shallow water, but is much more common. One reason being that they can handle partly shady forest pools and forest swamps, both too dark for Bar-wings. Source Credit: Bar-winged Skimmer, by Kevin Munroe.

I have observed Bar-winged Skimmer dragonflies at two locations in Huntley Meadows Park that provided habitat similar to Kevin’s recipe. Bar-winged Skimmer is no longer found at either place.

I have seen Bar-winged Skimmer at Sundew Bog, located in the Central Tract at Patuxent Research Refuge.

The Central Tract of the refuge is closed to public visitation due to the sensitive nature of much of the scientific work. Source Credit: Patuxent Research Refuge brochure.

Range map

Not all species of Skimmers are as common as I tend to think. For example, the following map shows all official records for Libellula axilena in the United States of America. As you can see, Bar-winged Skimmer is a relatively uncommon species of odonate.

What are the take-aways?

Many species of dragonflies in the Family Libellulidae (Skimmers) are habitat generalists and relatively easy to find almost anywhere there is water. In contrast, I think it’s fair to say Bar-winged Skimmer is a habitat specialist that is challenging to find.

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Yellow-sided Skimmer (female, male)

June 25, 2021

Thanks to a tip from fellow odonate enthusiast Michael Ready, I was able to add another species of dragonfly to my life list recently: Yellow-sided Skimmer dragonfly (Libellula flavida).

Female

The first Yellow-sided Skimmer dragonfly that I spotted was perched along the shoreline of a small pond at an undisclosed location in Prince William County, Virginia USA. This individual is a female, as indicated by her terminal appendages.

Female Yellow-sided Skimmers have a pair of flanges beneath their eighth abdominal segment that are used to scoop and hold a few drops of water when laying eggs (oviposition), hence the family name “Skimmer.” Remember that all dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back.

17 JUN 2021 | PNC. Wm. County | Yellow-sided Skimmer (female)

I followed the female from one perch to another, “working the shot.” The next two photos are full-frame (4,000 x 3,000 pixels), that is, uncropped.

17 JUN 2021 | PNC. Wm. County | Yellow-sided Skimmer (female)

Notice the amber color near the leading edge of her wings, a good field mark for L. flavida.

17 JUN 2021 | PNC. Wm. County | Yellow-sided Skimmer (female)

Male

According to Dr. Steve Roble’s excellent datasets for the Commonwealth of Virginia, the adult flight period for Yellow-sided Skimmer is from May 15 to September 21.

By mid-June most males, including this one, are completely covered by light-blue pruinescence that obscures the yellow coloration on the sides of their thorax. Look closely at the full-size version of the following photo and you should see the amber color near the leading edge of his wings.

17 JUN 2021 | PNC. Wm. County | Yellow-sided Skimmer (male)

Habitat

A small, seep-fed pond located in the forest provides ideal habitat for Yellow-sided Skimmer.

Habitat: Boggy ponds, seeps, slow streams, and weedy ditches. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Location 9094). Princeton University Press. Kindle Edition.

23 MAY 2018 | PNC. Wm. County | small, seep-fed pond

Notice the fallen tree that lies between the foreground and the pond in the background, nearly perpendicular to the stream. The tree is a barrier that slows the flow of the stream, creating the type of boggy, weedy habitat that Yellow-sided Skimmer prefers.

Range maps

Not all species of Skimmers are as common as I tend to think. For example, the following map shows all official records for Libellula flavida in the United States of America. As you can see, Yellow-sided Skimmer is a relatively uncommon species of odonate.

Zooming in to reveal the details shows few records reported for Northern Virginia, where I live.

What are the take-aways?

Many species of dragonflies in the Family Libellulidae (Skimmers) are habitat generalists and relatively easy to find almost anywhere there is water. In contrast, I think it’s fair to say Yellow-sided Skimmer is a habitat specialist that is challenging to find.

Related Resource: Libellula flavida Yellow-sided Skimmer on NatureServe Explorer. The conservation status for L. flavida in Virginia is “Vulnerable (S3).”

Copyright © 2021 Walter Sanford. All rights reserved.

Spangled Skimmer (mature male)

June 15, 2021

A Spangled Skimmer dragonfly (Libellula cyanea) was spotted near a small pond at an undisclosed location in Fairfax County, Virginia USA.

This individual is a mature male, as indicated by his deep blue pruinescence and terminal appendages. Contrast the appearance of this mature male Spangled Skimmer with a teneral female spotted on 13 May 2021 at a location in Prince William County, Virginia USA.

05 JUN 2021 | Fairfax County, VA | Spangled Skimmer (mature male)

This guy seemed to be unusually skittish.

05 JUN 2021 | Fairfax County, VA | Spangled Skimmer (mature male)

I followed him to three different perches before he decided the photoshoot was finished and flew into a nearby tree.

05 JUN 2021 | Fairfax County, VA | Spangled Skimmer (mature male)

Copyright © 2021 Walter Sanford. All rights reserved.

I was common, when common wasn’t cool.

June 8, 2021

Common Whitetail dragonfly (Plathemis lydia) was observed during a photowalk along a mid-size stream at an undisclosed location in Prince William County, Virginia USA.

This individual is an immature male, as indicated by his mostly brown coloration, pattern of wing spots, and terminal appendages.

13 MAY 2021 | PNC. Wm. County | Common Whitetail (immature male)

This photo is one of a few “warm-up shots” I took at the outset of my photowalk. I think it’s a good idea to be sure your camera gear is working as expected before you blow an opportunity to photograph something rare to uncommon by fiddling with camera settings.

Copyright © 2021 Walter Sanford. All rights reserved.

Turn! Turn! Turn!

May 21, 2021

Perceptive observers of nature notice gradual changes that indicate the change of season.

To everything (turn, turn, turn)
There is a season (turn, turn, turn)
And a time to every purpose, under heaven.
Source Credit: Turn! Turn! Turn! Song by The Byrds

For example, sighting a Spangled Skimmer dragonfly (Libellula cyanea) is a sure sign the subtle transition from spring to summer is underway.

13 MAY 2021 | PNC. Wm. County, VA | Spangled Skimmer (teneral female)

One of my mantras for wildlife photography is “Get a shot, any shot; refine the shot.” The preceding photo is one I took when I noticed the dragonfly; the following photo is one I took after slowly working my way into position for a better shot. Notice the dragonfly changed positions too, moving from one perch to another when I moved closer to her.

13 MAY 2021 | PNC. Wm. County, VA | Spangled Skimmer (teneral female)

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

Copyright © 2021 Walter Sanford. All rights reserved.


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