Posts Tagged ‘cerci’

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.

Black-shouldered Spinyleg (female)

August 13, 2021

A Black-shouldered Spinyleg dragonfly (Dromogomphus spinosus) was spotted by Michael Powell during a photowalk with me along a mid-size stream at an undisclosed location in Prince William County, Virginia USA.

This individual is a female, as indicated by her rounded hind wings and terminal appendages.

05 AUG 2021 | PNC. Wm. County | Black-shouldered Spinyleg (female)

We followed the female from one location…

05 AUG 2021 | PNC. Wm. County | Black-shouldered Spinyleg (female)

to another.

05 AUG 2021 | PNC. Wm. County | Black-shouldered Spinyleg (female)

I was able to take no more than three shots at each perch before she moved on to the next stop.

05 AUG 2021 | PNC. Wm. County | Black-shouldered Spinyleg (female)

Habitat

I’m not sure I’d call Black-shouldered Spinyleg a habitat specialist. I’ve seen and photographed D. spinosus along small streams in the forest, mid-size streams (like the one in this post), and large rivers.

Habitat: Rocky and muddy streams and rivers from small to large, more often in woodland. Also in rocky lakes in northern part of range. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 6416-6417). Princeton University Press. Kindle Edition.

Range map

The following map shows all official records for Dromogomphus spinosus in the United States of America. Given the wide range of lotic habitats where Black-shouldered Spinyleg is found, I’m puzzled by the fact that the species isn’t more widespread than it appears to be.

Related Resource: All posts in my blog tagged with the words “Black-shouldered Spinyleg dragonfly.”

Copyright © 2021 Walter Sanford. All rights reserved.

Anatomy of a male Tiger Spiketail

August 10, 2021

The following annotated image shows a Tiger Spiketail dragonfly (Cordulegaster erronea). This individual is a male, as indicated by his hamules, “indented” hind wings, and terminal appendages.

Hamules

Hamules? What are hamules?

hamules: paired structures that project from genital pocket under second segment and hold female abdomen in place during copulation Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 11618-116198). Princeton University Press. Kindle Edition.

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. Some species of dragonflies and damselflies — such as Ashy Clubtail versus Lancet Clubtail and Southern Spreadwing versus Sweetflag Spreadwing, to name a few — can be differentiated/identified with certainty only by examining the hamules under magnification.

Photo used with written permission from Michael Powell.

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

Indented hind wings

Male members of many families of dragonflies have “indented” hind wings near the body, with some notable exceptions.

Hind wing venation and shape can identify the sex of most dragonflies. Petaltails, darners (except Anax), clubtails, spiketails, cruisers, and some emeralds. Wing shape isn’t helpful to sex baskettails since they are largely the same. They are different in Cordulia, Dorocordulia, Somatochlora and to a lesser degree, Neurocordulia. Source Credit: Ed Lam, author and illustrator of Damselflies of the Northeast.

Terminal appendages

Identifying female versus male dragonflies and damselflies can be challenging but it’s a little easier when you know how to differentiate their terminal appendages.

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 dragonfly terminal appendages don’t look exactly the same for all species of dragonflies, but their function is identical.

Generally speaking, spiketail dragonflies have relatively small terminal appendages. That said, they must get the job done!

Related Resource: Tiger Spiketail dragonfly (male) – a blog post by Walter Sanford.

Copyright © 2021 Walter Sanford. All rights reserved.

 

Unicorn Clubtail dragonfly (male)

June 29, 2021

A Unicorn Clubtail dragonfly (Arigomphus villosipes) was photographed near the shoreline of a small pond at an undisclosed location in Fairfax County, Virginia USA.

This individual is a male, as indicated by his terminal appendages. 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”).

For those of you keeping score at home, notice male Unicorn terminal appendages have four points/prongs. Does that mean A. villosipes is an exception to the rule of three terminal appendages for male dragonflies? In a word, no.

05 JUN 2021 | Fairfax County, VA | Unicorn Clubtail (male)

The preceding photo shows a clear view of the male’s terminal appendages. Zoom-in on the full-size version of the photo and you should notice that the epiproct for Unicorn Clubtail is essentially a wide plate with two points/prongs.

Related Resource: Odonate Terminal Appendages – a permanent reference page in my blog featuring identification guides for most of the common species of odonates found in Virginia, and even some of the uncommon to rare species.

Copyright © 2021 Walter Sanford. All rights reserved.

 

Uhler’s Sundragon dragonfly (female)

April 20, 2021

Uhler’s Sundragon (Helocordulia uhleri) was spotted during a recent photowalk along a mid-size stream at an undisclosed location in Prince William County, Virginia USA.

13 APR 2021 | Prince William County, VA | Uhler’s Sundragon (female)

This individual is a female, as indicated by her rounded hind wings and terminal appendages. All female dragonflies have a pair of cerci (superior appendages) that have little or no function. Both the rounded hind wings and two cerci are visible clearly in the full-size version of the following photo.

13 APR 2021 | Prince William County, VA | Uhler’s Sundragon (female)

Just the facts, ma’am.

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 H. uhleri is 29 March to 27 June. The species is classified as common. Its habitat is “streams.”

Bear in mind, Dr. Roble’s records are for the entire state, therefore the adult flight period for H. uhleri seems to be longer than it is in reality. The adult flight period for a single site is probably no more than a month, and more likely around two-to-three weeks. For example, according to records for Northern Virginia maintained by Kevin Munroe, former manager of Huntley Meadows Park, the adult flight period for Uhler’s is 11 April to 05 May.

It’s also worth noting that the window of opportunity to see Uhler’s Sundragon closes rapidly after trees are in full leaf; this phenological event usually occurs by mid-April in the mid-Atlantic USA.

Is Uhler’s Sundragon common? I guess the answer to that question depends upon where you live. In Northern Virginia, Kevin Munroe classified H. uhleri as “rare.” In fact, I’m aware of only one location in Northern Virginia where Uhler’s Sundragon can be found with reasonable certainty although not in large numbers.

Copyright © 2021 Walter Sanford. All rights reserved.

Selys’s Sundragon dragonfly (male)

April 16, 2021

I discovered a Selys’ Sundragon dragonfly (Helocordulia selysii) during a recent photowalk with Michael Powell at an undisclosed location in Prince William County, Virginia USA. Selys’s Sundragon is a new species for my Life List of odonates and for Prince William County, VA. [Odonata Species (p. 1 of 2) — current as of 14 April 2021 — shows part of the species list for Prince William County before Selys’s was added.]

This individual is a male with a malformed abdomen. Notice his abdomen is twisted so that the terminal appendages aren’t in their usual alignment. The cerci should be on top and the epiproct should be on the bottom; they aren’t where they should be.

13 APR 2021 | Prince William County, VA | Selys’s Sundragon (male)

All male dragonflies have three terminal appendages, collectively called “claspers,” that are used to grab and hold female dragonflies during mating. Male dragonfly terminal appendages don’t look exactly the same for all species of dragonflies, but their function is identical. The misalignment of this Selys’s terminal appendages might be a problem when attempting to form the “wheel position” with females.

The Backstory

Mike Powell and I were men on a mission to photograph Uhler’s Sundragon dragonflies (Helocordulia uhleri). The sky was completely overcast when we arrived at our destination. According to the weather forecast, the sky was supposed to clear around 1:00 pm, and sure enough it did. Soon afterward, we spotted our first Uhler’s of the day and spent some time photographing several individuals.

All of the Uhler’s we saw were female. At some point I said to Mike (paraphrasing) “I need to photograph at least one male before we leave!” I walked a little farther downstream from a place where Mike was shooting macro photos of a very cooperative female Uhler’s. That’s when I spotted the male shown in the preceding photo.

My first impression was the dragonfly seemed to be noticeably smaller than the female Uhler’s we had been photographing. Turns out I was right! According to Dragonflies and Damselflies of the East by Dennis Paulson, Uhler’s are 41-46 mm in total length (4.1-4.6 cm) and Selys’s are 38-41 mm in total length (3.8-4.1 cm). For those of you keeping score at home, that’s only ~1.5″ long — small for many if not most dragonflies!

Related Resource: Selys’s Sundragon dragonfly – a blog post by Michael Powell, my good friend and photowalking buddy.

Copyright © 2021 Walter Sanford. All rights reserved.

MYN – Eastern Amberwing exuvia (anal pyramid)

March 9, 2020

An Eastern Amberwing dragonfly (Perithemis tenera) exuvia was collected by Joe Johnston on 07 August 2019 along Aquia Creek at Channel Marker No. 34, Stafford County, Virginia USA.

The specimen is probably from either Family Corduliidae (Emeralds) or Family Libellulidae (Skimmers).

The rule of thumb for differentiating Corduliidae exuviae from Libellulidae is as follows: It’s probably Corduliidae if the cerci are at least half as long as the paraprocts; it’s probably Libellulidae if the cerci are less than half the length of the paraprocts.

65mm (3x magnification) | ISO 100 | f/8 | 1/200 s | 0 ev

Look closely at the full-size version of the preceding photo, showing a close-up of the anal pyramid at 3x magnification. Notice the cerci are approximately half as long as the epiproct and slightly less than half the length of the paraprocts. It’s a close call, but the latter field mark indicates Family Libellulidae (Skimmers).

A step-by-step identification guide (to the species level) will be published in a follow-up post. Stay tuned!

Related Resources

Copyright © 2020 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.

Common Green Darner dragonfly (young male)

September 27, 2019

A mini-swarm of Common Green Darner dragonflies (Anax junius) was spotted at a dry vernal pool, Old Colchester Park and Preserve (OCPP), Fairfax County, Virginia USA. A few Black Saddlebags dragonflies were mixed in with the swarm of A. junius.

Some of the dragonflies were hawking smaller insects; others were resting on vegetation. It’s probable members of the swarm had stopped to rest and refuel before continuing their southward migration.

The following Common Green Darner dragonfly was perched in a bed of dried cattails.

18 SEP 2019 | OCPP | Common Green Darner (young male)

This individual is a young male, as indicated by his terminal appendages. Notice there are points on the tips of his cerci, as shown in the full-size version of the preceding photo. Female cerci are pointless, both literally and figuratively.

Related Resources

Copyright © 2019 Walter Sanford. All rights reserved.

Flashback to late-May 2019

September 16, 2019

Look closely at the following photo — there’s a dragonfly in there somewhere!

21 May 2019 | PNC. William County, VA | Lancet Clubtail (female)

A Lancet Clubtail dragonfly (Phanogomphus exilis) was spotted by Gary Myers at an undisclosed location in Prince William County, Virginia USA. The dragonfly is perched on leaf litter in a seepage area upstream from a small pond.

Female and male terminal appendages

This individual is a female, as indicated by her rounded hind wings and terminal appendages. (Notice the “bonus bug” to the right of the label for cercus.)

21 May 2019 | PNC. William County, VA | Lancet Clubtail (female)

Contrast the appearance of those female field marks with males of the same species.

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

Related Resource: Odonate Terminal Appendages — single-topic field guides for dragonflies and damselflies featuring both text and annotated photos.

Copyright © 2019 Walter Sanford. All rights reserved.


%d bloggers like this: