Archive for April, 2021

Common Whitetail dragonfly (immature male)

April 30, 2021

A Common Whitetail dragonfly (Plathemis lydia) was observed near a small pond during a photowalk with Michael Powell at Occoquan Regional Park (ORP).

This individual is an immature male, as indicated by his mostly brown coloration, pattern of wing spots, and terminal appendages. Part of his left fore wing is missing, probably as a result of an encounter with a predator.

28 APR 2021 | ORP | Common Whitetail (immature male)

Common Whitetail dragonflies are habitat generalists that can be found almost anywhere there is water. They are among the first species of dragonflies to appear during spring and the last to disappear in fall.

Copyright © 2021 Walter Sanford. All rights reserved.

Uhler’s Sundragon dragonfly (emergent female)

April 27, 2021

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

The dragonfly was perched on the exuvia from which it emerged; its cast skin was still clinging to a grass stem approximately six inches (6″) above the ground. The patch of grass was located two-to-three feet from the shoreline, where the stream current was slow-to-moderate. The stream bed was sandy and gently sloped near the site on land where the dragonfly larva stopped to eclose.

This individual is an emergent female, as indicated by her teneral appearance, rounded hind wings, terminal appendages, and subgenital plate.

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

The subgenital plate is located on the ventral side of the abdomen beneath segment eight.

Underneath Segment 8 there is either an ovipositor or a subgenital plate, depending upon the species [of dragonfly]. Both structures are for laying eggs and extend over Segment 9 and possibly beyond. Source Credit: Dragonflies of the North Woods, by Kurt Mead.

Remember that “Segment 8 and 9” refers to abdominal segments eight and nine (of 10), numbered from front to back.

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

The following graphic from Dragonflies and Damselflies of the East by Dennis Paulson shows the shape of the subgenital plate on our emergent female matches Uhler’s perfectly.

Graphic used with written permission from Dennis Paulson.

True Detective

Generally speaking, teneral odonates are more challenging to identify than most mature adult dragonflies and damselflies. Full disclosure: Neither Mike nor I were certain of the identity of the emergent female when we were shooting photographs in the field. “Shoot first and ask questions later” is one of my mantras for wildlife photography.

The most reliable way to identify odonate larvae to the species level is to rear them to maturity and emergence, that is, unless you’re fortunate to find a larva emerging in the field. Since an exuvia is essentially a nearly perfect shell of the last instar, it can be used to identify other specimens of the same species by pattern matching.

In this case, I used the exuvia to reverse-engineer the identity of the teneral dragonfly. Look closely at a lateral view of the exuvia, as shown in the following photo taken by Mike Powell. Notice there are dorsal hooks on abdominal segments seven, eight, and nine (S7-9). This distinctive field mark confirms the identity of the species as H. uhleri.

Photo used with written permission from Michael Powell.

Also notice Mike’s photo shows a clear view of the emergent female’s terminal appendages, as well as the subgenital plate on the underside of her abdomen.

How it all began, and ended.

The sky was almost completely overcast and it was cool and windy when I spotted the emergent female. Mike Powell and I observed the dragonfly for quite a while and there was little noticeable progress. According to Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, the process of emergence can take longer when the air temperature is cooler.

When the sky began clearing, Mike Powell and I decided to go to a nearby place where he had seen adult Uhler’s recently. Later the same day, we returned to the site of the emergent female; she was gone, so I collected the exuvia. I plan to publish a photo set of the exuvia in an upcoming blog post. To be continued.

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

It’s all about habitat, habitat, habitat.

April 23, 2021

Small streams and seeps in the forest are perfect places to look for habitat specialist dragonflies such as petaltails and spiketails.

An old place revisited.

The following photograph of a forest seep has been featured in my blog at least once in the past. The seep feeds a small pond; Gray Petaltail dragonflies (Tachopteryx thoreyi) can be found feeding and perching in sunny spots around the pond during late-May and early-June.

23 MAY 2018 | Prince William County, VA | forested seep

The seep is the habitat where Gray Petaltail larvae live most of their lives, not the pond. I always wondered how so many adult petaltails could emerge from this relatively small seep.

Turns out Michael Powell, my good friend and photowalking buddy, must have been wondering the same thing because he explored the area upstream from the small seep shown above and discovered several more seeps located close to the one near the pond.

The next photo shows Mike resting on a log along the edge of one of the seeps, near the confluence of two small streams. Notice the patch of skunk cabbage (Symplocarpus foetidus) growing in the seep — a good sign that you might be looking at habitat suitable for Gray Petaltail.

13 APR 2021 | Prince William County, VA | forested seep

A new place worth exploring further.

Mike also discovered another small stream in the forest when he was exploring for Uhler’s Sundragon (Helocordulia uhleri). The stream is located at the approximate midpoint between two trails, so I nicknamed it “Middle Creek.” Clever, huh? Note the patch of skunk cabbage growing in a seep alongside the stream. Did an alarm just go off in your head?

13 APR 2021 | Prince William County, VA | forested stream and seep

Mike and I are eager to explore the stream further, mainly looking for Gray Petaltail during late spring. Several species of spiketails might be found there as well.

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.

Tethered

April 13, 2021

“Tethered.” What does that word mean to a photographer? In its simplest sense, it’s when a camera is connected to a computer either by some type of cable or sometimes wirelessly.

“Tethered shooting” implies the photographer is able to control the camera remotely, either partially or completely.

Is there really a distinction between the two terms? I think so.

In my last two blog posts I mentioned that my older Fujifilm X-T1 mirrorless digital camera cannot be used for tethered shooting using either the free Fujifilm X Acquire 2 software or via some sort of HDMI Video Capture device. That being said, the Fujifilm X-T1 camera can be tethered to my computer in order to display the output from the HDMI port on the camera.

The section entitled “Viewing Pictures on TV” that appears on p. 108 of the Fujifilm X-T1 Owner’s Manual is shown below.

When the Fujifilm X-T1 is connected to my Apple MacBook Air computer via a MavisLink Video Capture Card and displayed on-screen using OBS Studio, the camera thinks the computer is a TV. Well, sort of.

OBS Studio | Properties for ‘Video Capture Device’

First, add a “Video Capture Device” to a “Scene” in OBS Studio. Select “USB Video” since the “HDMI Video Capture” device connects to the computer via USB. A colorful test pattern appears on screen, even when the camera is turned on.

When the “Play” button on the back of Fujifilm X-T1 camera is pressed, a small green LED in the upper-right corner of the camera turns on and the photos saved to the memory card in your camera are shown on-screen, one image at a time. Use the “D” pad on the back of the camera to cycle through all of the photos on the memory card. Press the “Play” button when you’re finished and the test pattern reappears in OBS Studio.

By the way, the photo shown in the preceding “Screenshot” of OBS Studio is one of the images I shot for Sumo Citrus still life, a recent blog post.

Copyright © 2021 Walter Sanford. All rights reserved.

What is it?

April 6, 2021

Ladies and gentlemen, children of all ages. It’s time for another exciting episode of “What is it?”

This episode is a little different because the name of the mystery item is printed clearly on the product itself. I guess the real mystery is two-fold: What does the acronym “HDMI” mean, and what does this video capture device do?

“HDMI” stands for “High-Definition Multimedia Interface.” The MavisLink Video Capture Card converts HDMI 4K 60FPS (from your digital camera) to USB 1080P 60FPS (on your computer) that can be either recorded or live streamed on video conferencing services.

“MavisLink” is a brand name that was recommended by Graham Houghton, a gentleman whose expertise I respect and opinion I value. It’s worth noting a quick Web search will reveal lots of video capture cards sold under different brand names that look identical to the MavisLink device shown above. Do they work as well as the one recommended by Graham? Who knows?

I plan to use the device in combination with Open Broadcaster Software (OBS Studio) to record the video and audio output from some of my digital cameras; the saved video clips will be featured in future “how to” blog posts.

So far I have tested the process with several of my cameras: My Panasonic Lumix DMC-FZ300 and Fujifilm X-T3 work; my Fujifim X-T1 doesn’t work.

I still need to test my older Canon EOS 5D Mark II. It should work but as far as I know the camera doesn’t feature “clean HDMI” output, that is, some or all of the info display on the camera viewfinder/LCD (e.g., the focus rectangle) is included in the output.

Related Resource: DSLR and Mirrorless Webcams Versus Capture over HDMI, by Graham Houghton (8:56). See the segment entitled “HDMI Capture” that begins at ~5:01 into the video.

Copyright © 2021 Walter Sanford. All rights reserved.


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