Posts Tagged ‘Libellula incesta’

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.

Slaty Skimmer dragonfly (mature male)

August 28, 2019

A Slaty Skimmer dragonfly (Libellula incesta) was spotted at Painted Turtle Pond, Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

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

16 AUG 2019 | Occoquan Bay NWR | Slaty Skimmer (mature male)

Habitat preference

Slaty Skimmer is a habitat generalist that can be found virtually anywhere there is water, such as a mid-size pond like Painted Turtle Pond.

This species is a true habitat generalist; only whitetails and pondhawks can be found in as many different habitat types. I’ve seen Slaties along river edges, sunny sections of woodland streams, ponds, lakes, swamps, old roads and flooded meadows. Dragonflies of summer, if you’re in any of these habitats June through September, you’re likely to come face to face with a Slaty Skimmer. Source Credit: Dragonflies of Northern Virginia, by Kevin Munroe.

Copyright © 2019 Walter Sanford. All rights reserved.

Previews of coming attractions

March 28, 2018

Several test photos were taken for an upcoming identification guide for exuviae from Slaty Skimmer dragonfly (Libellula incesta).

The exuvia has a mask-like labium with smooth crenulations, indicating this specimen is a member of the Family Libellulidae (Skimmers), the largest family of dragonflies.

No. 1 | Libellula incesta | exuvia (face-head-dorsal)

Also notice the exuvia has “pointed” eyes, rather than “rounded” eyes like the exuvia from a Carolina Saddlebags dragonfly (Tramea carolina) shown below.

No. 2 | Tramea carolina | exuvia (face-head)

The pointed- versus rounded eyes dichotomy is a somewhat subjective decision, but if you make the right choice then this marker can be used to narrow the range of possible Libellulidae genera.

Exuviae from three genera of Libellulidae have pointed eyes: Libellula (18 species); Orthemis (3 species); and Plathemis (2 species). Slaty Skimmer (Libellula incesta) is one of 18 species in the genus Libellula.

Exuviae from all other genera of Libellulidae have rounded eyes.

No. 3 | Libellula incesta | exuvia (dorsal)

This specimen needs to be rehydrated/relaxed in order to remove some distracting debris and reposition the legs for better photo poses.

No. 4 | Libellula incesta | exuvia (ventral)

To be continued…

The Backstory

A Slaty Skimmer dragonfly (Libellula incesta) nymph was collected by Bob Perkins on 29 May 2017 along Pine Creek in Carroll County, Virginia USA. The nymph was reared in captivity until it emerged on 29 June 2017 and metamorphosed into an adult male. This specimen is the exuvia from the nymph.

Copyright © 2018 Walter Sanford. All rights reserved.

The Blue Boy

August 6, 2017

Several Slaty Skimmer dragonflies (Libellula incesta) were spotted during a photowalk along Dogue Creek at Wickford Park, Fairfax County, Virginia USA. This individual is a male, as indicated by his terminal appendages and slaty blue coloration.

09 JUL 2017 | Wickford Park | Slaty Skimmer (male)

This guy was my constant companion while I was photographing a male Common Sanddragon perching on a small sandbar in the creek.

09 JUL 2017 | Wickford Park | Slaty Skimmer (male)

I nicknamed this dragonfly “The Blue Boy” because his rich blue-indigo color is reminiscent of an oil painting by Thomas Gainsborough.

Copyright © 2017 Walter Sanford. All rights reserved.

Summertime is skimmer time

July 31, 2017

Refer to the Dragonflies of Northern Virginia Calendar of Flight Periods by Kevin Munroe, former manager at Huntley Meadows Park. Notice the flight period for most Skimmers (Family Libellulidae) is centered on June, July, and August. Since meteorological summer is defined as June, July, and August, summertime is skimmer time.

A female Slaty Skimmer dragonfly (Libellula incesta) was spotted during a photowalk at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA, as indicated by her mostly black femora, brown face, and terminal appendages.

Female Slaty Skimmers have a pair of flanges beneath their eighth abdominal segment (S8) that are used to scoop water when laying eggs (oviposition), hence the family name “Skimmer.”

Female Slaty Skimmer dragonflies and female Great Blue Skimmer dragonflies (Libellula vibrans) look similar. The following blog post provides guidance regarding key field markers that can be used to differentiate the two species: Great Blue Skimmer dragonfly (young female).

Copyright © 2017 Walter Sanford. All rights reserved.

Slaty Skimmer dragonflies (mating pair)

March 7, 2017

Odonates (dragonflies and damselflies) are aquatic insects that spend most of their life as larvae that live in water; this stage of their life cycle can last from a few months to a few years, depending upon the species. Finally, they emerge from the water and metamorphose into adults in order to reproduce; their offspring return to the water and the cycle begins again.

A mating pair of Slaty Skimmer dragonflies (Libellula incesta) was spotted at Painted Turtle Pond, Occoquan Bay National Wildlife Refuge (OBNWR), Prince William County, Virginia USA. This pair is “in wheel”: the male is on the upper-left; the female on the lower-right.

A mating pair of Slaty Skimmer dragonflies (Libellula incesta) spotted at Painted Turtle Pond, Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA. This pair is "in wheel."

18 JUN 2016 | OBNWR | Slaty Skimmer (mating pair, “in wheel“)

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.

Copyright © 2017 Walter Sanford. All rights reserved.

Rivals

December 13, 2015

A Slaty Skimmer dragonfly (Libellula incesta) was spotted at Huntley Meadows Park. This individual is a mature male, as indicated by its coloration and terminal apppendages. A male Blue Dasher dragonfly (Pachydiplax longipennis) is shown in the background.

These two males were rivals, competing for one of two perches overlooking a wetland pool. I was amused by the smaller Blue Dasher’s aggressive behavior as he buzzed the larger Slaty Skimmer repeatedly, trying to recapture the prized perch he occupied before the Slaty showed up.

Copyright © 2015 Walter Sanford. All rights reserved.

Black Saddlebags dragonfly (male)

August 23, 2015

A Black Saddlebags dragonfly (Tramea lacerata) was spotted in the hemi-marsh at Huntley Meadows Park. This individual is a male, as indicated by its coloration and terminal appendages.

A Black Saddlebags dragonfly (Tramea lacerata) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a male.

05 JUL 2015 | Huntley Meadows Park | Black Saddlebags (male)

It is uncommon to see the broad-winged skimmers from the genus Tramea perching. Dragonflies are classified as either “fliers” or “perchers,” based upon their feeding habits. Black Saddlebags are fliers.

A Black Saddlebags dragonfly (Tramea lacerata) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a male.

05 JUL 2015 | Huntley Meadows Park | Black Saddlebags (male)

Black Saddlebags is one of at least five major species of dragonflies known to be migratory in North America. Broad hindwings is an adaptation that enables Black Saddlebags to glide easily when flying. Dragonflies expend less energy when gliding, an aide to long-distance migration. According to the axiom in biology/morphology, form follows function.

Slaty Skimmer dragonflies (Libellula incesta), such as the mature male shown below, look somewhat similar to Black Saddlebags. Slaty Skimmers are “perchers.” Slaty Skimmers aren’t migratory; notice their hindwings are narrower than Black Saddlebags.

Related Resource: A sampler of male dragonfly claspers (Part 2). (See “Skimmer Family,” Black Saddlebags dragonfly.)

Copyright © 2015 Walter Sanford. All rights reserved.

Slaty Skimmer dragonfly (female, laying eggs)

June 28, 2015

Slaty Skimmer (Libellula incesta) is a member of the Skimmer Family of dragonflies. Females lay eggs (oviposition) by skimming the water surface repeatedly, hence the family name “Skimmer“; two flanges beneath their eighth abdominal segment (S8) scoop water that is used to flick fertilized eggs toward shore, as illustrated in the following annotated image. Remember that all dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back.

A Slaty Skimmer dragonfly (Libellula incesta) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a mature female member of a mating pair.

10 JUN 2015 | Huntley Meadows Park | Slaty Skimmer (mature female)

The preceding still photo shows a mature female Slaty Skimmer dragonfly resting immediately after copulation.

The following movie shows the same female laying eggs in a large pool of water downstream from the central wetland area at Huntley Meadows Park on 10 June 2015.

Tech Tip: The preceding movie looks better viewed in full-screen mode.

Copyright © 2015 Walter Sanford. All rights reserved.


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