Posts Tagged ‘Otter Lake’

Macromia alleghaniensis exuvia

October 6, 2018

Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, collected an odonate exuvia on 07 June 2018 along either Little Otter Creek or Otter Creek near the place where both creeks are distributaries of Otter Lake in Amherst County, Virginia USA.

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 Macromiidae (Cruisers).

  • The specimen has a mask-like labium (prementum) that covers the face, as shown in Photo No. 1, characteristic of four families of odonates: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).
  • The teeth on the margins of the labium have a regular pattern. (The pattern reminds me of a “spork.”)
  • Its eyes are small, wide set, and stick up.
  • Image No. 2 shows there is a horn on the face-head, characteristic of Macromiidae.

Photo No. 1 shows a face-head view of the exuvia, magnified approximately three times life size (~3x).

No. 1 | Macromia alleghaniensis | exuvia (face-head)

Image No. 2 shows the top of the head of the exuvia, magnified approximately three times life size (~3x). Notice the prominent horn on the face.

No. 2 | Macromia alleghaniensis | exuvia (head-horn)

Step 2. Genus and species

Two dichotomous keys found on p. 27 of Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz, were used to determine the genus and species of the exuvia. Field marks that match this specimen are highlighted in boldface green text. Three boldface green asterisks (***) are used to highlight the thread for identification of this specimen.

Key to the Genera of the Family Macromiidae

***1b. Lateral spines of abdominal segment 9 do not reach to rearward level of tips of inferior appendages [paraprocts]; Sides of head somewhat convergent behind eyes to pair of low turbercules on hind angles; Lateral setae of labium = 6; Small dorsal hook on segment 10. [Macromia]

A small dorsal hook on abdominal segment 10 is characteristic of Genus Macromia.

No. 3 | Macromia alleghaniensis | exuvia (dorsal-lateral)

Look closely at the full-size version of Image No. 4. Notice the little “nub” on abdominal segment 10 (S10), below the underside of the dorsal hook on abdominal segment nine (S9). The same structure is labeled with a white question mark in Image No. 3.

No. 4 | Macromia alleghaniensis | exuvia (dorsal-lateral)

The lateral spines of abdominal segment 9 (S9) do not reach rearward to the tips of the inferior appendages (paraprocts).

No. 5 | Macromia alleghaniensis | exuvia (dorsal)

Key to the Species of Macromia

1a. Lateral spines of abdominal segments 8 and 9 directed straight to rearward. [illinoiensis]

***1b. Lateral spines of abdominal segments 8 and 9 incurved, especially 8. [alleghaniensis]

The lateral spines of abdominal segments 8 and 9 (S8-9) are incurved, especially segment 8 (S8), indicating this species is alleghaniensis.

No. 6 | Macromia alleghaniensis | exuvia (ventral)

This individual is probably a male, as indicated by what appear to be vestigial hamules located on the ventral side of abdominal segments two and three (S2-3).

Summary

A prominent horn on the face is a key field mark for the Family Macromiidae (Cruisers), a small dorsal hook on abdominal segment 10 is one characteristic of the Genus Macromia, and the lateral spines of abdominal segments 8 and 9 (S8-9) are incurved, indicating the species is alleghaniensis. Therefore this specimen is an Allegheny River Cruiser dragonfly (Macromia alleghaniensis).

Bonus Gallery

No. 7 | Macromia alleghaniensis | exuvia (face-head)

No. 8 | Macromia alleghaniensis | exuvia (dorsal-lateral)

No. 9 | Macromia alleghaniensis | exuvia (dorsal)

Related Resources

Tech Tips

The following equipment was used to shoot Photo/Image No. 3-9: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode. Photo/Image No. 1 and 2Canon MP-E 65mm Macro lens (manual focus only, set for ~3x magnification) plus the multiple-flash setup.

Image No. 2-8 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017: Image No. 2 (eight photos); Image No. 3 (six photos); Image No. 4 (four photos); Image No. 5 (five photos); Image No. 6 (five photos); Image No. 7 (seven photos); Image No. 8 (seven photos).

Copyright © 2018 Walter Sanford. All rights reserved.

Macromiidae larvae/exuviae are horny

October 4, 2018

A prominent horn on the face is a key field mark for all larvae/exuviae in the Family Macromiidae (Cruisers).

The first image shows the top of the head of an exuvia from an Allegheny River Cruiser dragonfly (Macromia alleghaniensis), collected by Mike Boatwright on 07 June 2018 at Otter Lake in Amherst County, Virginia USA.

07 June 2018 | Amherst County, VA | exuvia (head-horn)

The next photo shows the top of the head of an Allegheny River Cruiser larva reared by fellow Virginian Bob Perkins, providing an excellent view of both the horn and antennae (2).

Image used with permission from Bob Perkins.

Tech Tips

The following equipment was used to shoot the composite image of the exuvia: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (set for 3x); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode.

Adobe Photoshop CC 2017 was used to create the focus-stacked composite image from eight photos.

Bob Perkins’ photo of the larva, taken on 03 October 2018, was shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Copyright © 2018 Walter Sanford. All rights reserved.

Latest focus stacking workflow

October 2, 2018

I shot a small set of photos for a focus stack showing the ventral view of an unknown species of odonate exuvia. There are five “slices,” focused from head-to-tail along the body only (no shots focused on legs/feet).

The following gallery shows the five focus points along the body of the specimen, highlighted by a red square.

Although this photo set has fewer “slices” than I have been using to create focus stacks recently (~15-20 photos, on average), the resulting composite image (shown below) is perfectly in focus along the entire body and is serviceable for the purpose of identifying the genus and species of this specimen.

07 June 2018 | Amherst County, VA | exuvia (ventral)

The preceding composite image shows an exuvia from an unknown species of dragonfly (possibly River Cruiser sp.), collected by Mike Boatwright on 07 June 2018 at Otter Lake in Amherst County, Virginia USA. This individual probably is a male, as indicated by vestigial hamules located on the underside of abdominal segments two and three (S2-3).

Shooting the Photo Set

  • Set the camera for Manual Mode.
  • Set the lens for manual focus and turn off image stabilization (when the camera/lens is mounted on a tripod).
  • Compose the image so the frame is a little bigger than the scene you really want. This will give you some wiggle room during post-processing.
  • Set external flash(es) for Manual Mode. (~1/16 power is a good starting point.)
  • Select single focus point; move focus point around image.
  • Live View plus 5x and 10x magnification.
  • Drive mode: 10s timer.
  • DON’T MOVE THE CAMERA. Shoot as many images as necessary.

Advance Preparation – Edit Photos Using Aperture [or Lightroom]

Although Apple discontinued development of/support for Aperture years ago, the desktop application still works and in many ways I prefer Aperture over Adobe Lightroom.

  • Edit one image: make all adjustments except spot and patch, vignette, and BFX.
  • Right-click on edited photo; select “Lift Adjustments.”
  • <Replace> <Stamp Selected Images>
  • Add metadata: Lift and Stamp selected images.
  • Select images (to be focus stacked); export as TIFFs (16-bit), 300 dpi; save in folder entitled either “TIFF” or “TIFF versions.” File / Export… / Version… [Export Preset: TIFF – Original Size (16-bit)]

Focus Stacking Using Adobe Photoshop

Launch Photoshop.

  • File / Scripts / Load Files into Stack… [Alternate option: Add Open Files <OK>] Do not check the box for “Create Smart Object after Loading Layers.” By default, Ps creates a new document called “Untitled1.”
  • Select all layers.
  • Edit / Auto-Align Layers; Auto <OK>
  • Edit / Auto-Blend Layers; Stack Images, Seamless Tones and Colors <OK>
  • Duplicate all masked layers to a new document. Layer / Duplicate Layers… / Document: New / Name: Backup-copy
  • Select Untitled1: Layer / Merge Layers. (Ps merges all layers into one TIFF, named after first file in sequence.)
  • Straighten and Crop as necessary.
  • Duplicate the layer; append name with “Spot Healing.” [Alternate option: drag layer to copy icon]
  • Remove dust spots from the image: Spot Healing Brush: 27-54 pixels, Content-Aware.
  • Duplicate the layer; append name with “HPF.” [Alternate option: drag Spot Healing layer to copy icon]
  • Select the top layer: Filter / Other / High Pass…; adjust until you can just see outline of image <OK>; change Normal to Overlay. [Don’t oversharpen! ~2.6 used for the composite image featured in this blog post.]
  • Untitled1: Save As… TIFF.
  • Backup-copy (of masked layers): Save As… either PSD or Large Document Format (for documents larger than 2 GB).
  • Import composite TIFF file [Untitled1.tif] into Aperture [or Lightroom]: add additional keywords, as appropriate [e.g., annotated, composite image, focus stack, Photoshop]; Export using BorderBFX.

Tech Tips

The following equipment was used to shoot the composite image (shown above): Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode. A Sunpak LED-160 Video Light (with a white translucent plastic filter) was used to add soft light to the underside of the white “stage” used for posing the specimen.

Adobe Photoshop CC 2017 was used to create the focus-stacked composite image from five photos.

Copyright © 2018 Walter Sanford. All rights reserved.


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