Field marks for identification of S. rogersi

The following annotated images illustrate field marks that can be used for identification of Sable Clubtail dragonfly (Stenogomphurus rogersi). Although there is some redundancy among the images, repetition is a good strategy for learning.

Male

Male Sable Clubtails have eyes that are green to turquoise in color, with a black occiput located between the eyes. They have a thin, black abdomen that flares to a small club featuring thin yellow flanges on abdominal segments seven through nine (S7-9).

The abdomen is marked with small pale dorsal triangles (S3-7) and tiny pale lateral spots. The number of dorsal triangles can vary individually and/or geographically, ranging from S3-5 to S3-7.

08 JUN 2018 | Fairfax County, VA | Sable Clubtail (male)

Dennis Paulson, originator of the classification system for thoracic stripes in the Family Gomphidae (Clubtails), describes T1-4 as follows.

T1–2 broad and complete, touching at ends and often with stripe between them restricted and topped with spot; T3–4 fine, T3 incomplete. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 6089-6093). Princeton University Press. Kindle Edition.

Note: T1-4 refers to the dark areas located on the sides of the thorax, not the lighter colored lines and spots. Due to space limitations, thoracic stripes are labeled using a numeral only (e.g., “1”) rather than a letter and numeral (e.g., “T1”).

08 JUN 2018 | Fairfax County, VA | Sable Clubtail (male)

Their face is pale, marked with variable black crosslines (as shown in the inset photo, below).

08 JUN 2018 | Fairfax County, VA | Sable Clubtail (male)

Male Sable Clubtails, like all male dragonflies, have three terminal appendages, collectively called “claspers.” All male clubtail dragonflies have indented hind wings.

Female

Female Sable Clubtails have a noticeably thicker abdomen than males. The occiput is a pale color, rather than black. Dorsal triangles, located on abdominal segments three through seven (S3-7), are much larger than those found on males. The lateral spots are somewhat larger as well.

05 JUL 2018 | Fairfax County, VA | Sable Clubtail (female)

Female Sable Clubtails, like all female dragonflies, have a pair of cerci (superior appendages) that have little or no function. All female clubtail dragonflies have rounded hind wings.

Related Resource: Stenogomphurus rogersi exuvia.

Copyright © 2018 Walter Sanford. All rights reserved.

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