Notice the large reddish areas on the top of the eyes. These areas are referred to as the dorsal foveae—so named because they are on the top (dorsal) surface of the eyes, and are the parts of the eyes with the sharpest vision (analogous to the vertebrate fovea). The name is ironic because the word fovea is Latin for "pit," and indeed the fovea (area of sharpest vision) of a vertebrate's eye is a pit on the surface of the retina. In the case of a dragonfly, the fovea is not a pit, but it is the area of sharpest vision.
Here's another view of dorsal foveae in dragonflies, this time on a Cardinal Meadowhawk.
One of the interesting aspects of dorsal foveae is that the ommatidia (individual eyes) in them are rather large, and point primarily in one direction. This gives the sharp vision mentioned above. It also means that when you look directly at the dorsal foveae, you see an exceptionally large pseudopupil, as shown below.
My, what big eyes you have!
This effect is perhaps best seen in Blue Dashers. Take a look for the "big eyes" next time you get a good look at a Blue Dasher. You can read more about the eyes of dragonflies in my new field guide: Common Dragonflies and Damselflies of the Pacific Coast.
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