Dragonflies: Thriving on Vision

 Photography Tips:
1. Wear purple or blue clothing to photograph dragonflies.
2. To put six to nine feet between my lens and a dragonfly, I use a telephoto of 400 to 500 mm focal length, and place an extension tube between camera and lens.  

Dragonflies and damselflies are colorful, active hunters. They depend on their vision to fly, hunt, and thrive. Dragonflies possess a finely tuned visual system with globe-like, genetically evolved eyes that empower them to catch their prey, and see a variety of light wavelengths, in ways that are quite beyond our vision.

We learned in school that our vision works with red, green and blue sensitive cells. We may know that our vision also depends on the chemistry of our three visual opsins, or our eyes light- sensitive proteins. For instance, the first half hour after you walk into a dark cave, your eyes adapt, using an opsin called rhodopsin, a light sensitive chemical that improves your night vision to let you see detail.

Enter the dragonfly. It has evolved a wider range of vision. One study of 12 dragonfly species genetics found that each one has 11 to 33 different visual opsins, thanks to dynamic gene multiplication (Ryo Tahashi et al, Proceedings National Academy of Sciences, USA, 2015 Mar 17; 112-11). Tahashi and colleagues found  the evolution of the diverse opsin genes in dragonflies is relevant to their ecology.  In the daytime, brightly-colored male dragonflies make a territory at an open space around riverside, pond, forest edge, or tree canopy. There, they patrol. With flight faster than we can see, they defend the territory against other males. They attempt to mate with females.

True dragonflies, but not damselflies, tend to have a twilight flight just before and after sunset. At that time, they dine. They pursue mosquitos, midges, flies and other insects that emerge after sundown. Thus, we can thank the over 1500 species of dragonflies for ridding us of numerous biting bugs. 

Photography Tip:
   Wear darker blue or purple clothes and skip the bright colored fabrics, when you try to get close to a dragonfly. Dragonflies have a dorsal visual system and a ventral visual system that are sensitive to different color wavelengths and their visual system, in general, is more sensitive to the 500 to 700 nanometer wavelengths, and somewhat less tuned to the 300-500 nanometer wavelengths, those of dark blue and purple.