Tuesday, February 21, 2017

Species Spotlight: Blue Dasher

Well, we've finished up with the dragonflies with "black" in their name, and are now onto the "blue" dragonflies. First up, the Blue Dasher.

This is one of my favorite dragonflies for a number of reasons. First, it's very widespread in its distribution, so you're likely to see one almost anywhere you go dragonflying. Here's it's range map:

The only blank areas are the upper plains and Rockies.

Second, it's very cute and photogenic. The Blue Dasher strikes delightful poses for the photographer, and lands repeatedly on favorite perches. Here are a couple shots of the male Blue Dasher:

The blue color of the Blue Dasher is produced not by pigments, but by light scattering from the microscopic structures on its body—in much the same way that the scattering of light gives the sky its blue color.

The large area on the top of the Blue Dasher's eyes, where you can just make out the lattice of individual eyes (the ommatidia), is known as the dorsal fovea. It is the part of the eye that gives the dragonfly its highest resolution vision. If you look straight down on the dorsal fovea you see large black pseudopupils, as shown below. (By the way, the white spots are reflections of the sun.)

Female Blue Dashers are completely different in appearance. They are cryptically colored with a brown background and numerous yellow stripes:

The Blue Dasher—beautiful, widespread, easy to photograph. This species has it all.

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