A Black-shouldered Spinyleg dragonfly (Dromogomphus spinosus) was spotted during a photowalk along the Potomac River at Riverbend Park. This individual is a female, as indicated by its terminal appendages and the shape of its hind wings.
Now you see it, now you don’t.
The first photo set shows the female dragonfly eating what appears to be a teneral damselfly.
Dragonflies have two small antennae on their face, located in front of their large compound eyes. Zoom in on the full-size version of the following photo. Notice there is a small drop of water surrounding the antenna located in front of the left eye; the water droplet isn’t visible in the first photo.
The Backstory: The dragonfly was perching on a narrow beach along the river. In order to move into position for a lateral view of the dragonfly, I had to wade in the muddy river. Almost immediately I stepped in a seemingly bottomless hole. My left foot sank quickly into mud that would have been over the top of my knee-high rubber boot, so I jerked my foot out of the mud; the sudden motion created a big splash of water that landed in front of the dragonfly. Much to my amazement, the dragonfly didn’t move! I didn’t notice the water drop until I edited this photo set.
The water drop is still visible in the next photo. The damselfly is gone except for its wings and part of a leg.
By the time the dragonfly moved to a nearby perch, the water drop on its face had evaporated.
Perching on vegetation
The following dorsal view of the same dragonfly shows its hind wings are rounded near the body, a good field marker for female clubtail dragonflies.
The last photo shows a lateral view of the dragonfly. Look closely at the side of its thorax. Black-shouldered Spinyleg is the only clubtail with broad, pale green thoracic stripes. Also notice the broad dark stripe on the “shoulder” of the thorax, hence the common name “Black-shouldered.”
Copyright © 2016 Walter Sanford. All rights reserved.