The specimen is approximately 3.3 cm (~1.3 in) long, measured from head to tail. Notice the mid-dorsal hooks/spines located along the abdomen of the body.
At first I thought the exuvia might be a species from the genus Stylurus, based upon the mid-dorsal spine on abdominal segment nine (S9). After careful examination of two excellent photo-illustrated PowerPoint presentations by Kevin Hemeon at NymphFest 2016 (see Related Resources, below), I noticed none of the species in the genus Stylurus have dorsal hooks. That’s when I realized the specimen must be D. spinosus. Eureka! Source Credit: Dromogomphus spinosus exuvia – a blog post published on 28 June 2019 by Walter Sanford.
Related Resources
The following PowerPoint presentations by Kevin Hemeon are available in the “Files” section of the Northeast Odonata Facebook group. Direct links to the documents are provided below.
Odonate Exuviae – a hyperlinked list of identification guides to many species of odonate exuviae from seven families of dragonflies and three families of damselflies.
Tech Tips
The photograph featured in this blog post is a “one-off,” that is, a single photo rather than a focus-stacked composite image. The camera lens was set for f/16; the camera body was set for ISO 160 and a shutter speed of 1/250 s.
Two external flash units were used to create the white background by cross lighting the front of a piece of white plastic; another flash was used to light the subject. A Sunpack LED 160 was used as a focusing aid.
RAW FILE CONVERTER EX 3.0 was used to convert one RAW (RAF) file to a TIFF file. The TIFF file was edited using Apple Aperture and sharpened using Photoshop.
Male odonates have two sets of sex organs: primary genitalia located on abdominal segment nine (S9); and secondary genitalia located on abdominal segments two-to-three (S2-3).
This male specimen has too much dirt on S9 to see the primary genitalia; the secondary genitalia are visible on S2-3. I plan to annotate the image in order to highlight select anatomical features.
Odonate Exuviae – a hyperlinked list of identification guides to many species of odonate exuviae from seven families of dragonflies and three families of damselflies.
The subject was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique. The exposure was increased by 0.3 stop during post-processing in order to attain a pure white background.
One external flash unit was used to create the white background and two others to light the subject. A Sunpack LED 160 was used as a focusing aid.
RAW FILE CONVERTER EX 3.0 was used to convert six (6) RAW (RAF) files to TIFF files. In a departure from my usual workflow, the TIFF files were loaded into Adobe Photoshop CC 2017 in order to create the focus stacked composite image. The composite image was edited using Apple Aperture and sharpened using Photoshop.
Tech Take-aways
Notice there is some color fringing (mostly reds) that is especially noticeable on the front legs and antennae, as well as along the edges of the posterior abdomen. I have been experimenting with a new technique for backlighting the subject. It appears I need to add another layer of diffusion between the light source and the subject.
There is also some “softness” along the edges of the abdomen that could be the result of too few focus points for the shape of the body, which in turn, could have caused artifacts in the composite image.
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.
walter sanford's photoblog 