Posts Tagged ‘Occoquan Bay National Wildlife Refuge’

Epitheca cynosura exuvia

April 26, 2017

On 13 April 2017, a late-stage emergent teneral female Common Baskettail dragonfly (Epitheca cynosura) was observed at Painted Turtle Pond during a photowalk around Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

Several dragonfly exuviae were collected near the same location as the emergent teneral female. All of the exuviae look identical, although there is some variation in size. A two-step process was used to verify the genus and species for one of the larger exuvia.

  • Determine the family.
  • Determine the genus and species.

This specimen is approximately 22 mm (~0.87 in) in length.

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 that covers the face, characteristic of four families: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).
  • There is no horn on top of 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 [See Photo No. 7.]: It’s probably Corduliidae if the cerci are at least half as long as the paraprocts. [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).

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

Notice that dorsal hooks are present and well developed on most abdominal segments.

No. 4 | Common Baskettail (Epitheca cynosura) | exuvia (dorso-lateral)

A lateral view of the exuvia provides a good look at the labium, also known as the mentum, a two-segment hinged “jaw” that is used to grab food: the prementum is the segment of the labium closer to the mouth; the postmentum is the segment closer to the base of the head.

The white filaments that extend from the split in the thorax (as shown in Photo No. 1-7) are breathing tubes, artifacts of the unique respiratory system of dragonfly nymphs.

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

A closer view of the head shows two “bumps” that may be a pair of tubercles.

Step 2. Genus and species

Characters from Identification Keys to Northeastern Anisoptera Larvae, dichotomous keys compiled by Ken Soltesz, were used to identify the genus and species for the exuvia. Although palpal/mental setae were not examined, all other characters match Epitheca cynosura.

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

Alternate Key to the Genera of the Family Corduliidae, p. 29.

Key to the species of the genus (subgenus) Tetragoneuria, p. 32.

No. 7 | Common Baskettail (Epitheca cynosura) | exuvia (anal pyramid)

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

The last photo shows a ventral view of the exuvia. The vestigial hamuli located between abdominal segments two and three (S2-3) strongly suggests this individual is a male, therefore this specimen probably is not the same exuvia from which the teneral female emerged.

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

Tech Tips:

The following equipment was used to shoot all of the preceding photographs: Canon EOS 5D Mark II digital camera, in manual mode; Canon EF100mm f/2.8L Macro lens (set for manual focus) plus a Kenko 20mm macro automatic extension tube; Canon 580EX II external flash tethered to the camera by a coiled six-foot Vello Off-Camera TTL Flash Cord for Canon Cameras, off-camera, in manual mode; the Canon flash optically triggered a small Nissin i40 external flash (in SF mode) used for backlight; and a Sunpak LED-160 Video Light with a white translucent plastic filter used for side light.

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resources:

Editor’s Note: Sincere thanks to Sue Gregoire, Kestrel Haven Migration Observatory, for verifying my tentative identification, and for sharing some good odonate nymph knowledge regarding vestigial hamuli!

Copyright © 2017 Walter Sanford. All rights reserved.

Late-stage emergent baskettail dragonfly

April 18, 2017

Common Baskettail dragonfly (Epitheca cynosura) was spotted at Painted Turtle Pond during a photowalk around Occoquan Bay National Wildlife Refuge (OBNWR), Prince William County, Virginia USA. This individual is a late-stage emergent teneral female.

I photographed the process of emergence from the first sighting to the time when the teneral dragonfly flew away: I shot 23 photos in approximately 16 minutes; time is compressed by showcasing six (6) select photos taken at major milestones during the event.

The following photo is the first image from a time-series documenting the emergence of the teneral female. Elapsed time is expressed in hh:mm:ss format, e.g., 00:00:00 is the time when I spotted the emergent teneral female, and 00:16:08 is the total elapsed time.

13 APR 2016 | 11:38:41 am EDT | Elapsed time: 00:00:00

Notice the drop of fluid at the tip of the abdomen. Emerging dragonflies pump fluid into their wings, causing the wings to expand. Next, the same fluid is withdrawn from the wings and used to expand the abdomen. Excess fluid is expelled afterward.

13 APR 2016 | 11:40:48 am EDT | Elapsed time: 00:02:07

The next photo shows the first time the wings opened.

13 APR 2016 | 11:48:55 am EDT | Elapsed time: 00:10:14

Then the wings closed again and remained closed for a while.

13 APR 2016 | 11:51:02 am EDT | Elapsed time: 00:12:21

The wings reopened a few minutes later. Notice that several wings are malformed slightly.

13 APR 2016 | 11:54:14 am EDT | Elapsed time: 00:15:33

Finally, the wings open up, and very soon the teneral adult flies away. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 468). Princeton University Press. Kindle Edition.

The teneral female dragonfly flew away immediately after the last photo in the time-series.

13 APR 2016 | 11:54:46 am EDT | Elapsed time: 00:16:08

This individual is a female, as indicated by her cerci (superior appendages) and thick abdomen. Common Baskettail females have shorter cerci and a thicker abdomen than males of the same species.

Exuviae (in situ)

Several dragonfly exuviae were spotted at Painted Turtle Pond. The exuviae were identified using a dichotomous key for dragonfly larvae; they are cast skins from Common Baskettail.

13 APR 2017 | OBNWR | Common Baskettail (exuvia)

These exuviae are not the one from which the teneral female featured in this post emerged.

13 APR 2017 | OBNWR | Common Baskettail (exuvia)

Copyright © 2017 Walter Sanford. All rights reserved.

Common Baskettail dragonfly (male)

April 16, 2017

A Common Baskettail dragonfly (Epitheca cynosura) was spotted near Painted Turtle Pond during a photowalk at Occoquan Bay National Wildlife Refuge (OBNWR). Common Baskettail is a member of Family Corduliidae (Emeralds); this species is seen during early spring in mid-Atlantic United States like Virginia.

I thought this might be a Slender Baskettail dragonfly (Epitheca costalis) due to narrowing of its abdomen. Turns out that was wishful thinking.

13 APR 2017 | OBNWR | Common Baskettail (male)

This individual is a male, as indicated by his terminal appendages. The curved shape of the cerci (superior appendages) is a key field marker for Common Baskettail; in contrast, the cerci for Slender Baskettail tend to be more parallel. Thanks to Mike Boatwright and Paul Guris, members of the Northeast Odonata Facebook group, for reminding me of this pearl of wisdom!

I think baskettail cerci look “rubberized,” like the handles of metal tools made for working with electricity. Whenever I see this distinctive field marker, shown clearly in the following photos, I know the dragonfly is probably a species of baskettail.

13 APR 2017 | OBNWR | Common Baskettail (male)

The last photo shows a dorso-lateral view of the male dragonfly. Notice the epiproct (inferior appendage) is visible clearly in this photo.

13 APR 2017 | OBNWR | Common Baskettail (male)

Also notice the light-colored spots on the hairs covering the body of the dragonfly. The following article by John Abbott suggests the spots may be some type of pollen.

Related Resource: Identification of Male Epitheca (Tetragoneuria) in Texas, by John C. Abbott.

Copyright © 2017 Walter Sanford. All rights reserved.

Autumn Meadowhawk (mature female)

April 4, 2017

25 OCT 2016 | OBNWR | Autumn Meadowhawk (mature female)

The preceding photograph shows an Autumn Meadowhawk dragonfly (Sympetrum vicinum) perching on fall foliage at Occoquan Bay National Wildlife Refuge (OBNWR), Prince William County, Virginia USA. This individual is a mature female, as indicated by her terminal appendages, coloration, and tattered wings.

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.

, ?

March 1, 2017

I’m guessing you might be asking yourself, “What’s up with the title of this blog post?” It must be either a typo or mistake, right? No, it’s another case of acceptable uncertainty.

The following butterfly is either an Eastern Comma (Polygonia comma) or Question Mark (Polygonia interrogationis). I can’t tell the difference between these two species unless I see the distinctive punctuation marks that appear on the underside of their wings. In this case, I saw the dorsal side only.

Some naturalists say you can differentiate Eastern Comma and Question Mark by their relative size, but hey, they’re so similar in size I think that field marker is useless unless the two species are side-by-side.

The preceding butterfly was spotted during a photowalk along Deephole Point Road at Occoquan Bay National Wildlife Refuge (OBNWR), Prince William County, Virginia USA.

Editor’s Note: Thanks to Michael Powell for identifying the butterfly featured in this post as an Eastern Comma. For details, see Michael’s comment on the post.

Copyright © 2017 Walter Sanford. All rights reserved.

Uncommonly attractive Common Buckeye

February 27, 2017

A Common Buckeye butterfly (Junonia coenia) was spotted during a photowalk along Deephole Point Road at Occoquan Bay National Wildlife Refuge (OBNWR), Prince William County, Virginia USA.

Although I would never wear clothes with the same color palette as the Common Buckeye, somehow it just works for them!

Copyright © 2017 Walter Sanford. All rights reserved.

Another Monarch butterfly

February 5, 2017

Monarch butterfly (Danaus plexippus) was spotted during a photowalk along Deephole Point Road at Occoquan Bay National Wildlife Refuge (OBNWR), Prince William County, Virginia USA.

A Monarch butterfly (Danaus plexippus) spotted at Occoquan Bay National Wildlife Refuge, Fairfax County, Virginia USA. This individual is a male.

25 OCT 2016 | OBNWR | Monarch butterfly (male)

This individual is a male, as indicated by the presence of scent scales on his hind wings. Notice the dark wing spots clearly visible in the dorsal view (shown above) and faintly visible in the ventral view (shown below). Technically, the wing spots are called “androconia.”

A Monarch butterfly (Danaus plexippus) spotted at Occoquan Bay National Wildlife Refuge, Fairfax County, Virginia USA.

25 OCT 2016 | OBNWR | Monarch butterfly (male)

Copyright © 2017 Walter Sanford. All rights reserved.

Peopoll’s Choice Awards – Top 10 Photos of 2016

January 22, 2017

Ladies and gentlemen, the people have spoken. It’s time to announce the winners of the Peopoll’s Choice Awards for my Top 10 Photos of 2016. The Top 10 photos were selected using reader feedback. Sincere thanks for your participation!

Award-winning photos are presented in order of most-to-least votes. I cast the tie-breaking votes for the last four winners (No. 7-10), chosen from five photos that received the same number of your votes. In other words, I selected one of five photos to omit.

No. 1

No. 2

No. 3

No. 4

No. 5

No. 6

No. 7

No. 8

No. 9

No. 10

Editor’s Note: The following location codes are used in some photo captions, shown above.

Copyright © 2017 Walter Sanford. All rights reserved.

Zebra Swallowtail butterfly

January 12, 2017

A late-season Zebra Swallowtail butterfly (Eurytides marcellus) was spotted during a photowalk along Deephole Point Road at Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

The left hindwing looks like it might be malformed.

Copyright © 2017 Walter Sanford. All rights reserved.


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