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!
Odonate exuviae collecting sites (a blog post featuring video and still photos by Joseph Johnston that provide a guided tour of some places along Aquia Creek where Joe collects odonate exuviae, including the one featured in this blog post)
Tech Tips
This specimen was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique. I used the new variation on my old MYN studio rig and I’m still satisfied with the results.
Four photos were used to create a composite image: one photo focused on the thorax; and three other photos focused on abdominal segments two-three (S2-S3), seven (S7), and nine (S9).
Two key field marks can be used to quickly identify both the genus and species of this specimen. Notice that abdominal segment nine (S9) is elongated, strongly suggesting this individual is a member of the genus Stylurus. The large dorsal hook of abdominal segment nine (S9) that overhangs segment 10 (S10) is a key marker for southern specimens of plagiatus.
Odonate exuviae collecting sites (a blog post featuring video and still photos by Joseph Johnston that provide a guided tour of some places along Aquia Creek where Joe collects odonate exuviae, including the one featured in this blog post)
Tech Tips
This specimen was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique. I used the new variation on my old MYN studio rig and I’m still satisfied with the results.
Four photos were used to create a composite image: one photo focused on the head; and three other photos focused on abdominal segments five (S5), seven-eight (S7-S8), and 10 (S10).
Notice the specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in the preceding photo. This field mark indicates the exuvia is from either Family Aeshnidae (Darners) or Family Gomphidae (Clubtails). Other field marks, including club-like antennae and the shape of the body, indicate this individual is a species of clubtail.
My next blog post will feature a dorsal-lateral view of the exuvia that clearly shows the field marks that indicate both genus and species.
Odonate exuviae collecting sites (a blog post featuring video and still photos by Joseph Johnston that provide a guided tour of some places along Aquia Creek where Joe collects odonate exuviae, including the one featured in this blog post)
Tech Tips
This specimen was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique. I used the new variation on my old MYN studio rig and I’m still satisfied with the results.
This blog post features more photos of an exuvia from an unknown species of odonate that was collected by Joe Johnston on 07 August 2019 along Aquia Creek at Channel Marker No. 34, Stafford County, Virginia USA.
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.
I’m having a hard time seeing the cerci clearly. If I’m seeing what I think I’m seeing, then the cerci are at least half as long as the paraprocts and the exuvia is from Family Corduliidae (Emeralds).
In order to verify my tentative identification, I need to use a higher magnification macro lens (such as my Canon MP-E 65mm Macro lens) in order to shoot a close-up view of the anal pyramid/terminal appendages (see inset diagram, lower-left corner).
This specimen was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique. I used the new variation on my old MYN studio rig and I’m still satisfied with the results.
An exuvia from an unknown species of odonate was collected by Joe Johnston on 07 August 2019 along Aquia Creek at Channel Marker No. 34, Stafford County, Virginia USA.
This relatively small exuvia is ~1.2 to 1.3 cm in length. Notice the dorsal hooks on the exuvia are “cultriform,” that is, shaped like a pruning knife.
This specimen was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique.
I experimented with a new variation on my old MYN studio rig. The new set-up seems to work well, although the question remains “Does it work well consistently?” I added a second external flash unit that is used to backlight a piece of translucent white plastic (the background), and I physically separated the clear plastic “stage” from the white background. More info and photos will be featured in a follow-up blog post.
I took some quick-and-dirty test shots using a new piece of photo gear in combination with some old gear. The focus (no pun intended) was more about testing the camera rig and less about posing and lighting the subject perfectly.
~16mm (86mm, 35mm equivalent) | ISO 100 | f/4.5 | 1/400 s | -2.66 ev
The following video shows a “boater’s-eye view” of some sites where odonate exuviae have been collected by Joseph Johnston along Aquia Creek, located in Stafford County, Virginia USA. Joe is an avid boater and sport fisherman who kindly agreed to be my “Eyes on the Aquia,” always on the lookout for odonate exuvia to share with me.
The first photo gallery features still images of several spots shown in the preceding video. Joe estimates the water is ~5-6 feet deep outside the channel markers, and much deeper in the middle of the creek.
Joe’s boat is somewhere between the long boat docks (lower-right quadrant) and Government Island (near center), as shown in an aerial view of Aquia Creek provided by Google Maps.
The last photo gallery features still images of several exuviae, shown in situ before Joe collected the specimens. The first photo shows where it all began, when Joe collected his first dragonfly exuvia for me on 20 June 2018.
Joe Johnston is an avid boater and sport fisherman who kindly agreed to be my “Eyes on the Aquia,” always on the lookout for odonate exuvia to share with me. On 18 July 2018, Joe collected an especially interesting specimen from Aquia Creek in Stafford County, Virginia USA.
Abdominal segment nine (S9) is elongated, strongly suggesting this individual is a member of the genus Stylurus (Hanging Clubtails).
Did you notice the spider carcass that photobombed my test shots of the exuvia? Look for the spider along the upper-edge of the thorax in the dorsal view; lower-edge in the ventral view.
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 Laura’s Clubtail is 20 June to 26 September. The species is rare to uncommon. Its habitat is streams and rivers.
Tech Tips
The following equipment was used to shoot both of the macro photographs featured in this post: Fujifilm X-T1 digital camera; Fujifilm MCEX-11 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. Actually, back-button focus was used to autofocus the image and adjusted manually as necessary. That’s also a Fujifilm thing. Camera settings: focal length 80mm (120mm, 35mm equivalent); f/16; 1/500s.
Notice that abdominal segment nine (S9) is elongated, strongly suggesting this individual is a member of the genus Stylurus. The large dorsal hook of abdominal segment nine (S9) that overhangs segment 10 (S10) is a key marker for southern specimens of plagiatus.
The “working distance” for the 11mm Fujifilm extension tube/Fujinon 80mm macro lens combo, that is, the distance from the front of the lens barrel to the subject, is long enough to be able to use the lens hood.
Hotspots from external flash units, technically known as specular highlights, are more noticeable sometimes when the flash heads are closer to the subject. It appears the lens hood may have reduced that problem; more experimentation is required to be sure.
Joe Johnston is an avid boater and sport fisherman. On 20 June 2018, Joe and his brother Loren were fishing together on Aquia Creek in Stafford County, Virginia USA.
Fish require food and shelter. Sometimes fish shelter near trees that have fallen into water, or the wooden pilings of boat docks. Joe and Loren were casting artificial fishing lures toward one of several docks that extend far into Aquia Creek, when Loren’s lure snagged on one of the pilings. When Joe moved his boat alongside the piling in order to retrieve the fishing lure, Loren noticed an odonate exuvia on the side of the piling. Joe and Loren kindly collected several exuviae, including this one, and shared them with me. Thanks, gentlemen!
Tech Tips
The following equipment was used to shoot both of the macro photographs featured in this post: Fujifilm X-T1 digital camera; Fujifilm MCEX-11 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. Actually, back-button focus was used to autofocus the image and adjusted manually as necessary. That’s also a Fujifilm thing. Camera settings: focal length 80mm (120mm, 35mm equivalent); f/16; 1/500s.
