“Generic Baskettail” (definitely not a Cruiser)

A larva/nymph in the Family Corduliidae (Emeralds) was collected by Bob Perkins on 02 December 2017 from a pond in Orange Park, Florida (USA). The larva died before it metamorphosed into an adult.

As you can see by looking at a close-up image of the face-head at 3x magnification, there is no horn on the face of the specimen. Therefore this individual is not a member of Family Macromiidae (Cruisers), as I speculated in my last blog post.

“Generic Baskettail” larva (preserved specimen) | face-head

Knowing the limits of our expertise

Although I still need to key out the specimen carefully, at this point I’m certain Bob is correct — the larva is a member of the Family Corduliidae (Emeralds). The question that remains unanswered is “Which genus/species?” We may never know the answer, as Bob and I have reached the limit of our experience and expertise.

I did a quick scan of Paulson’s [book], looking at the Emerald Family. Here, according to the range maps, are the possibilities for Orange Park [FL]. I believe you can see why I stopped at “generic basketttail.” Source Credit: Bob Perkins.

• Slender Baskettail (Epitheca costalis)
• Common Basketball (Epitheca cynosura)
• Prince Baskettail (Epitheca princeps)
• Mantled Baskettail (Epitheca semiaquea)
• Sepia Baskettail (Epitheca sepia)
• Florida Baskettail (Epitheca stella)
• Alabama Shadowdragon (Neurocordulia alabamensis)
• Umber Shadowdragon (Neurocordulia obsoleta)
• Fine-lined Emerald (Somatochlora filosa)
• Coppery Emerald (Somatochlora georgiana)
• Mocha Emerald (Somatochlora linearis)

What do you think the identity is? Most of the items in the preceding species list feature links to photos of odonate larvae/exuviae. See the links to BugGuide from the scientific names in the list.

Related Resource: Test shots: “Generic Baskettail?”

Tech Tips

Four (4) photos were used to create the preceding focus-stacked composite image. A single focus point was positioned over the face, between the antennae. At a magnification ratio of 3:1, it’s difficult to manually focus on a single point — the slightest movement around the macro rig changes focus unintentionally. A simple work-around for this problem is to take several shots of the same focus point and create a composite image of the photos.

The following equipment was used to shoot the preceding composite image: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (set for f/16 at 3x); a Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and a single external flash set for “Slave” mode — a Godox TT685C Thinklite TTL Flash fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier. A Sunpak LED-160 Video Light was used to add fill light to the top of the subject.

Auto power-off was disabled for the camera and external flash units.

Adobe Photoshop CC 2017 was used to create the focus stack, as well as spot-heal and sharpen the final output.

Copyright © 2019 Walter Sanford. All rights reserved.

Tags: Family Corduliidae (Emeralds), gear talk, larva, nymph