At least 11 Cobra Clubtail dragonflies (Gomphurus vastus) were spotted during a photowalk with Michael Powell in Fairfax County, Virginia USA, including 10 females and one male. This blog post features photos of the first two females that I spotted.
No. 1a
08 JUN 2020 | Fairfax County, VA | Cobra Clubtail (female)
This individual is a female, as indicated by her terminal appendages and rounded hind wings. Notice the injury to her right rear leg.
08 JUN 2020 | Fairfax County, VA | Cobra Clubtail (female)
No. 1b
Inspired by Fred Siskind’s portfolio of dew-covered insects, Mike Powell and I are on a never-ending quest to find and photograph dew-covered odonates. The last photo shows my best effort to date.
As we were photographing female No. 1a, I noticed another individual perched nearby. No. 1a was perched in a sunny spot where most of the morning dew had evaporated; No. 1b was perched in a shady spot where everything was still covered by dew.
08 JUN 2020 | Fairfax County, VA | Cobra Clubtail (female)
Unfortunately, this female was quite skittish so her glamor shoot was one-and-done.
What is dew and how does it form?
Dew forms when the atmosphere is cooled until its temperature reaches the “dew point temperature” and water vapor in the atmosphere (an invisible gas) condenses to become liquid water. (The temperature when this phase change occurs is also known as the “frost point temperature.”)
The dew point temperature varies depending upon the amount of moisture in the air. Typical dew points in the mid-Atlantic states are in the 60s and 70s during the summer months, 40s and 50s during spring and fall, and 20s and 30s during winter.
Check your local weather forecast to see whether the predicted overnight low air temperature will reach the dew point temperature. Sometimes close is good enough, as surfaces that are good radiators of thermal energy can cool a thin layer of air to the dew point.
Related Resources
- Dewpoint (AMETSOC)
- Dew Point vs Relative Humidity (NWS/NOAA)
- Observed Dew Point Temperature (UIUC)
Copyright © 2020 Walter Sanford. All rights reserved.
Tags: Cobra Clubtail dragonfly, Family Gomphidae (Clubtails), female, Gomphurus vastus, terminal appendages
walter sanford's photoblog 
June 12, 2020 at 9:05 am |
Walter, it occurred to me today reading your Cobra blog that people might enjoy hearing more about the type of environment that the particular species inhabit. The actual place does not need to be disclosed, but it could educate readers how to locate odes In there own region. Perhaps it would expand readership as well.
June 12, 2020 at 8:09 pm |
Thanks for your suggestion, Timothy. The habitat for Cobra Clubtail is described by most field guides as “large rivers.” In this case, the Potomac River near Washington, D.C. Do you live in the area? I have provided a lot of “actionable intel” regarding where to look for dragonflies, especially some of the rare-to-uncommon species. https://waltersanford.wordpress.com/odonate-habitats/
June 12, 2020 at 4:40 pm |
Enlarging your dew-covered Clubtail helped show how beautiful she is with jewel-like droplets all over her! Very nice photographic series for this species, Walter.
I’ll have to travel a bit north to find one, it seems.