Another Common Sanddragon

Common Sanddragon dragonfly (Progomphus obscurus) was spotted by my good friend Mike Powell during a photowalk along a small stream in the forest at an undisclosed location in Prince William County, Virginia USA.

This individual is a male, as indicated by his “indented” hind wings and terminal appendages.

21 JUN 2019 | PNC. William County, VA | Common Sanddragon (male)

It’s possible the subject is the same male we saw a short distance upstream from this location.

21 JUN 2019 | PNC. William County, VA | Common Sanddragon (male)

Adult flight period

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 P. obscurus is from May 15 to September 19. The species is classified as common. Its habitat is “sandy streams.”

Bear in mind, Dr. Roble’s records are for the entire state, therefore the adult flight period for P. obscurus seems to be longer than it is in reality. The adult flight period for a single site is probably shorter — more likely around two months. For example, according to records for Northern Virginia maintained by Kevin Munroe, former manager of Huntley Meadows Park, the adult flight period for Commom Sanddragon is 29 May to 06 August.

Cut Banks and Sand Point Bars

Here’s a quick lesson on the geomorphology and basic hydrology of meandering streams, as it relates to odonates such as the Common Sanddragon that Mike and I observed along a small stream in the forest.

Streamflow is faster along cut banks and slower along sand point bars. As a result, erosion occurs along cut banks and deposition occurs along sand point bars.

P. obscurus — like the male featured in this post — can be found perching on sand point bars, usually facing the water.

Source Credit: The preceding image is a file from the Wikimedia Commons, United States Geological Survey.

Tech Tips

The first photo is uncropped, that is, full resolution for the Panasonic Lumix DMC-FZ300 superzoom bridge camera (4,000 x 3,000 pixels). Needless to say, I was fairly close to the subject!

The second photo is cropped in order to eliminate some distracting elements near the edges of the image.

Copyright © 2019 Walter Sanford. All rights reserved.

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