Archive for February, 2017

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.

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Widow Skimmers at Riverbend Park

February 25, 2017

A couple of Widow Skimmer dragonflies (Libellula luctuosa) were spotted while hunting for clubtail dragonflies along the Potomac River at Riverbend Park, Fairfax County, Virginia USA. Riverbend Park is a “big river” habitat, so I was surprised to see Widow Skimmers.

Habitat Lakes, ponds, and pools in slow streams of all kinds with mud bottoms and usually much vegetation, in open and wooded habitats. Common at farm ponds and other created habitats. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 9061-9063). Princeton University Press. Kindle Edition.

Male

The first photo features a mature male, as indicated by his coloration, pattern of wing spots, and terminal appendages. This individual has mated many times, as shown by scratches on the white pruinescence covering his abdomen.

Female

A female is shown in the last two photos, as indicated by her coloration, pattern of wing spots, and terminal appendages.

Copyright © 2017 Walter Sanford. All rights reserved.

Acceptable uncertainty

February 23, 2017

An unknown species of damselfly from the Family Coenagrionidae (Narrow-winged Damselflies) was spotted at the stormwater management pond located at Mason Neck West Park. This individual is a female, as indicated by her terminal appendages.

I thought the damselfly might be a mature female Rambur’s Forktail damselfly (Ischnura ramburii), based upon the fact that I’d seen an immature female Rambur’s Forktail on 03 October 2016 at the same location. I consulted the experts of the Northeast Odonata Facebook group for verification of my tentative identification.

It’s a female bluet, probably Familiar [Bluet] but it has a hint of a carina, so it might be Big [Bluet], but the eyespots look more like Familiar. Female Rambur’s does not have shoulder stripes. Source Credit: Dr. Michael Moore. Michael is an active contributor to the Dragonfly and Damselfly Field Guide and ID App.

Difficult though it may be for me to accept, sometimes it’s impossible to identify odonates with certainty based upon a single photograph. This is especially true for many species of female damselflies.

Copyright © 2017 Walter Sanford. All rights reserved.

Malformed Cobra Clubtail dragonflies

February 21, 2017

I took 255 photographs during my first photowalk along the Potomac River at Riverbend Park, Fairfax County, Virginia USA, including lots of photos of Cobra Clubtail dragonflies (Gomphurus vastus). I noticed several malformed individuals when I reviewed the entire photo set recently (in search of look-alike species of clubtail dragonflies). None of the malformations prevented the dragonflies from functioning normally.

The first Cobra Clubtail is a male with a slightly crimped right hind wing, where a small part of the wing failed to fully inflate during emergence.

The next individual is a female. Notice that abdominal segment seven (S7) was crimped during emergence. (All dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back.)

The last individual is a male. Notice his left front leg is missing. The male is either malformed or he lost the leg due to injury.

A Cobra Clubtail dragonfly (Gomphurus vastus) spotted at Riverbend Park, Fairfax County, Virginia USA. This individual is a male; its left front leg is missing. Two dark face bars are field markers that can be used to differentiate Cobra Clubtail from other similar looking species of clubtails.

16 MAY 2016 | Riverbend Park | Cobra Clubtail (male, missing leg)

Two thick dark face bars are field markers that can be used to differentiate Cobra Clubtail from other similar looking species in the Family Gomphidae (Clubtails): Midland Clubtail (Gomphus fraternus) has no face bars; Splendid Clubtail (Gomphus lineatifrons) has thin dark face bars.

Tech Tips:

Shutter Priority mode was used for the first two photographs. Aperture Priority mode was used for the last photo, in order to increase the depth of field. As you can see, the depth of field at f/7.1 was insufficient for the tip of the dragonfly abdomen to be in focus. Typically, I wouldn’t publish the last photo, but I made an exception because it is the only photo I took that shows the face bars clearly.

Copyright © 2017 Walter Sanford. All rights reserved.

More power!

February 19, 2017

Like Tim “The Tool Man” Taylor, I like more power. (Grunt, grunt.) Actually, I need more power for some of the macro photography that I do, especially when I’m shooting small specimens such as odonate exuviae.

For the past few months, I’ve experimented with several ways to get more “oomph” from my Canon EF100mm f/2.8L Macro lens. I’ve tested three types of photo gear used in combination with the macro lens including extension tubes, a close-up filter, and a tele-extender.

The first photograph shows the following equipment, from left-to-right: Canon EOS 5D Mark II digital camera; Canon Extender EF 1.4x II (white); Kenko 20mm macro automatic extension tube; Canon EF100mm f/2.8L Macro lens; 67-52mm step-down ring; 52-42mm step-down ring; Raynox DCR-250 close-up filter (covered by lens cap).

Canon EOS 5D Mark II macro photography kit.

Canon EOS 5D Mark II macro photography kit.

For most macro subjects, my “base kit” includes the 100mm macro lens plus a 20mm extension tube. Adding one or more extension tubes reduces the minimum focusing distance of the lens. Adding a close-up filter enables me to zoom in closer to the subject. The tele-extender effectively changes the focal length of the macro lens from 100mm to 140mm, resulting in a 1 f/stop loss of light. Some photographers contend that adding a tele-extender can result in a loss of sharpness. Your results may vary from mine, but I find the increased magnification that results from using a tele-extender is worth a small loss of sharpness.

The Canon Extender EF 1.4x II is incompatible with the Canon EF100mm f/2.8L Macro lens — it is impossible to connect the two devices directly. It’s worth noting that incompatible doesn’t mean they don’t work together — they do, as long as an extension tube is added in-line between the tele-extender and lens.

The last photograph shows the following equipment, couterclockwise from the upper-left: “snap-on universal adapter” for Raynox DCR-250 close-up filter; Raynox close-up filter mounted on a 52-43mm step-down ring; and a 67-52mm step-down ring.

Several mounting adapters for Raynox DCR-250 close-up filter.

Several mounting adapters for Raynox DCR-250 close-up filter.

The Raynox DCR-250 close-up filter comes with a “snap-on universal adapter” for mounting the filter on lenses with a filter size from 52-67mm. The adapter clips on the front of a lens the same as a lens cap. In my opinion, that’s OK for use in a home photo studio but less than ideal for use in the field.

I bought two inexpensive step-down rings that can be used to mount the close-up filter more securely: a 52-43mm step-down ring enables me to mount the Raynox DCR-250 on either the “Nifty 50” (a 50mm lens for my Canon DSLR) or Panasonic DMC-FZ150 superzoom bridge camera, my go-to kit for photowalking; a 67-52mm step-down ring enables me to connect the 52-43mm/Raynox close-up filter combo (shown above) with my Canon 100mm macro lens.

In case you’re wondering whether vignetting is a problem when using two step-down rings with the Canon 100mm macro lens, it isn’t. As it turns out, the front lens element is recessed quite a bit from the lens barrel so the step-down rings cover little if any glass.

Related Resources:

Afterthoughts

Two thoughts occurred to me after this post was published.

  1. As a result of limited testing, I concluded that it is possible to stack two or three extension tubes in order to achieve the same result as using a tele-extender without any loss of sharpness. Problem is, the minimum focusing distance is so small that the working distance between the lens and subject is too close for comfort. Adding the tele-converter provides more magnification at a slightly longer working distance.
  2. Caution: Connect the 52-43mm step-down ring to the 67-52mm step-down ring BEFORE connecting the combo to the 100mm macro lens. Otherwise there is some risk of scratching the front element of the macro lens.

Copyright © 2017 Walter Sanford. All rights reserved.

Gomphurus vastus exuvia

February 17, 2017

10s, maybe 100s of adult Cobra Clubtail dragonflies (Gomphurus vastus) were spotted on 16 May 2016 during a photowalk along the Potomac River at Riverbend Park, Fairfax County, Virginia USA. Cobra Clubtails were the only species of odonate observed in a period of several hours.

A Cobra Clubtail dragonfly (Gomphurus vastus) spotted at Riverbend Park, Fairfax County, Virginia USA. This individual is a male.

No. 1 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (adult male)

A single exuvia (shown below) from an unknown species of dragonfly was collected with permission from park staff. If adult Cobra Clubtail dragonflies were common, then the specimen is probably a Cobra Clubtail exuvia, right? Let’s test our hypothesis.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 2 | Cobra Clubtail (Gomphurus vastus) | exuvia (face-head)

A two-step process was used to identify the genus and species of the exuvia.

  1. Determine the family.
  2. Determine the genus and species.

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 Gomphidae (Clubtails).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like). [See Photo No. 3.]
  • Antennae are club-like (not thin and thread-like, as in Aeshnidae). [See Photo No. 3.]
  • Eyes not exceptionally large compared to the size of the head (not large, as in Aeshnidae). [See Photo No. 3.]
A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 3 | Cobra Clubtail (Gomphurus vastus) | exuvia (face-head)

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

Step 2. Genus and species

Gomphidae is the second largest family of dragonflies, so it can be challenging to identify some specimens to the genus and species level.

Characters from two dichotomous keys were used to identify the exuvia, in part, due to confusion caused by the fact that the name for the genus to which Cobra Clubtail belongs was changed recently from Gomphus to Gomphurus. As a result, the workflow for identifying this specimen was a little “jumpier” than usual.

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

Dichotomous Key 1

Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz. Cobra Clubtail (Gomphus vastus), p. 15, Key to the species of the genus Gomphurus.

  • 1a – Strongly hooked palpal lobes with few teeth (3-5). Gomphurus group I (2) [See Photo No. 8.]
  • 2a – Length 27-30 mm. (vastus) [See Photo No. 4, below.]
A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 4 | Cobra Clubtail (Gomphurus vastus) | exuvia (dorsal)

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

Dichotomous Key 2

“Gomphus complex” (= Gomphini) – Clubtails, Odonata Nymphs of Michigan.

  • 1b. Middorsal length of Ab9 [S9] less than half its basal width (fig); length of Ab10 [S10] < 0.50x its width (fig) – 6 [See Photo No. 6.]
  • 6b. Lateral spines of Ab9 close to Ab10, markedly longer than those on Ab8 (fig) [S8]; abdomen appears dorsoventrally flattened (fig) – Gomphurus, 8 [See Photo No. 6.]
  • 8b. Apical margin of median lobe of prementum straight or slightly convex (fig) – 9 [See Photo No. 8.]
  • 9a.(8b). End hook of lateral lobe of labium strongly incurved, extending far past apex of the truncate, 3 to 4 lateral teeth next to it (fig) – Gomphurus vastus

No. 5Cobra Clubtail (Gomphurus vastus) | exuvia (posterior)

The preceding photograph shows a wider view of the posterior end of the abdomen. A closer view of the anal pyramid helps to illustrate several of the morphological characters described in Dichotomous Key 2.

No. 6Cobra Clubtail (Gomphurus vastus) | exuvia (anal pyramid)

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

The basal width of abdominal segment nine (S9) was measured in a straight line from edge-to-edge across the abdomen. The same distance would be longer if it were measured along the joint between abdominal segments eight and nine (S8 and S9). Either way the basal width is measured, the middorsal length is less than half of the basal width.

Since the middorsal length of abdominal segment 10 (S10) is clearly less than its basal width, the character wasn’t illustrated in the preceding annotated image.

Looking carefully at the anal pyramid, notice the cerci (sing. cercus) are slightly shorter than the epiproct, and the epiproct is almost as long as the paraprocts.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 7 | Cobra Clubtail (Gomphurus vastus) | exuvia (ventral)

Photo No. 7 shows a wider view of the ventral side of the specimen. Zooming in on the prementum helps to illustrate some of the morphological characters described in Dichotomous Key 2.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

No. 8 | Cobra Clubtail (Gomphurus vastus) | exuvia (prementum)

(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, off-camera, in manual mode; Canon 580EX external flash, off-camera, in manual mode; and a Yongnuo YN-622C-TX E-TTL II Wireless Flash Controller for Canon plus a two-pack of Yongnuo YN-622C II E-TTL Wireless Flash Transceivers for Canon.

Raynox DCR-250 close-up filter was used for Photo No. 3, 6, and 8. A Canon Extender EF 1.4x II was used for more magnification in Photo No. 8. Adding the tele-extender results in a 1 f/stop loss of light; additional backlight was added to the scene using a Nissin i40 external flash unit (off-camera, in SF mode).

Adobe Photoshop CC 2017 was used to annotate selected images.

The following photograph of another dragonfly exuvia was taken in-situ along the shoreline of the Potomac River using a Panasonic DMC-FZ150 superzoom bridge camera and Canon 580EX Speedlite, my go-to kit for photowalking. There were many exuviae clinging to the concrete retaining wall shown in the photo. Photo No. 1 was taken using the same camera-flash combo.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) photographed in situ at Riverbend Park, Fairfax County, Virginia USA.

No. 9 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (exuvia, in situ)

Related Resources:

Editor’s Note: Sincere thanks to Sue Gregoire, Kestrel Haven Migration Observatory, for her kind mentorship. Sue patiently provides guidance regarding the scientific jargon that can make it either challenging (at best) or impossible to understand many dichotomous keys for the identification of odonate larvae/exuviae. Like every good teacher, Sue doesn’t “give me a fish” — she teaches me how to fish. Thanks again, Sue!

Copyright © 2017 Walter Sanford. All rights reserved.

Blue-faced Meadowhawk (male, malformed)

February 15, 2017

Blue-faced Meadowhawk dragonfly (Sympetrum ambiguum) was spotted near a vernal pool at Huntley Meadows Park (HMP). This individual is a male, as indicated by his coloration and terminal appendages.

The male’s abdomen is slightly malformed. The malformation is more noticeable in the preceding photo and easy to overlook in the following photo.

Copyright © 2017 Walter Sanford. All rights reserved.

Russet-tipped Clubtail dragonflies (males, eating)

February 13, 2017

Two Russet-tipped Clubtail dragonflies (Stylurus plagiatus) were spotted during photowalks at Mulligan PondJackson Miles Abbott Wetland Refuge (JMAWR). Both individuals are males, as indicated by the large russet-colored club at the end of their abdomen, “indented” hindwings (see annotated image), and their terminal appendages.

Members of the genus Stylurus are known as “Hanging Clubtails” because they usually perch hanging vertically from trees, unlike most other species of clubtails that perch horizontally on the ground.

Most of them spend much time in flight over water, leading to speculation whether species of this genus may feed in flight rather than from a perch like most other clubtails. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 6127-6128). Princeton University Press. Kindle Edition.

Both of the male Russet-tipped Clubtails featured in this post were observed feeding from a perch in a tree, although a sample size of two may be insufficient for drawing a meaningful conclusion.

22 September 2016

The first individual is eating a Multicolored Asian Lady Beetle (Harmonia axyridis) .

A Russet-tipped Clubtail dragonfly (Stylurus plagiatus) spotted at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a male, eating a Multicolored Asian Lady Beetle (Harmonia axyridis).

22 SEP 2016 | JMAWR | Russet-tipped Clubtail (male, eating)

The next photo is my favorite in the set. The color, clarity, and composition combine to create a beautiful canvas for conveying the brutality of the eat-or-be-eaten natural world.

A Russet-tipped Clubtail dragonfly (Stylurus plagiatus) spotted at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a male, eating a Multicolored Asian Lady Beetle (Harmonia axyridis).

22 SEP 2016 | JMAWR | Russet-tipped Clubtail (male, eating)

The last photo was shot using Aperture Priority mode in order to achieve maximum depth of field.

A Russet-tipped Clubtail dragonfly (Stylurus plagiatus) spotted at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a male, eating a Multicolored Asian Lady Beetle (Harmonia axyridis).

22 SEP 2016 | JMAWR | Russet-tipped Clubtail (male, eating)

27 September 2016

The last individual is eating an unknown species of winged insect.

A Russet-tipped Clubtail dragonfly (Stylurus plagiatus) spotted at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a male, eating an unknown winged insect.

27 SEP 2016 | JMAWR | Russet-tipped Clubtail (male, eating)

Copyright © 2017 Walter Sanford. All rights reserved.

Teneral

February 11, 2017

Two species of teneral dragonflies were spotted on the same day at nearly the same location in Huntley Meadows Park.

teneral: adult after it has just emerged, soft and not definitively colored Source Credit: Glossary, Some Dragonfly Terms by Dennis R. Paulson.

Both species are members of the Family Libellulidae (Skimmers). Based upon my experience, early September seems late in the year for these two species to emerge!

Blue Dasher

A Blue Dasher dragonfly (Pachydiplax longipennis) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a teneral male.

02 SEP 2016 | Huntley Meadows Park | Blue Dasher (teneral male)

This individual is a teneral male Blue Dasher dragonfly (Pachydiplax longipennis), as indicated by his terminal appendages, coloration, and the tenuous appearance of its wings. The coloration of immature male Blue Dashers resembles females of the same species.

A Blue Dasher dragonfly (Pachydiplax longipennis) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a teneral male.

02 SEP 2016 | Huntley Meadows Park | Blue Dasher (teneral male)

Eastern Pondhawk

An Eastern Pondhawk dragonfly (Erythemis simplicicollis) spotted at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is a teneral male.

02 SEP 2016 | Huntley Meadows Park | Eastern Pondhawk (teneral male)

An Eastern Pondhawk dragonfly (Erythemis simplicicollis) was spotted near the same location where the Blue Dasher dragonfly was observed. This individual is a teneral male, as indicated by his terminal appendages, coloration, and the tenuous appearance of its wings. The coloration of immature male Eastern Pondhawks resembles females of the same species.

Copyright © 2017 Walter Sanford. All rights reserved.

Beautiful butterflies can be ugly!

February 9, 2017

Butterflies are beautiful, right? Usually. And they feed on beautiful flowers, right? Not always, as shown below.

An Eastern Tiger Swallowtail butterfly (Papilio glaucus) spotted at Accotink Bay Wildlife Refuge, Fairfax County, Virginia USA. This individual is a male, feeding on scat.

20 MAY 2016 | ABWR | Eastern Tiger Swallowtail (male)

An Eastern Tiger Swallowtail butterfly (Papilio glaucus) was spotted along Great Blue Heron Trail at Accotink Bay Wildlife Refuge (ABWR), Fairfax County, Virginia USA. This individual is a male, feeding on mineral salts in scat (possibly raccoon).

Copyright © 2017 Walter Sanford. All rights reserved.


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