TRR photo by Ed Wesely
Note the white patches on this chalk-fronted corporal. Atop its head, at the front, are a pair of compound eyes that allow it to see in every direction. (Click for larger version)

Chalk-fronted Corporals. On a cool, damp Memorial Day, this “chalk-fronted corporal” dragonfly chose to perch on a pair of trousers I’d hung on the clothesline. Dragonflies of this species are “frequent fliers” in spring and early summer.

The common name makes me wonder if chalky patches on the backs of the males reminded someone of an army corporal. The scientific name, Libellula julia, seems even more puzzling.

As a male matures, a chalky color develops on its thorax and upper abdomen, but is generally absent from the thorax of females. It’s been described as a kind of “bloom” that “sits on top of the cuticle (skin), hiding the colors underneath.”

TRR photo by Ed Wesely
Bulging compound eyes encircle the head of this individual like a pair of saddlebags. Note how small raindrops adhere to its back and to both eyes. (Click for larger version)

The substance contains compounds that reflect ultra violet light, but its precise function is uncertain.

Dragonflies, sometimes called “mosquito hawks” by country folk, are guided to mosquitoes and other prey by bulging eyes that contain about 10,000 to 28,000 individual lenses. Each lens acts as a simple eye, but a minute brain coordinates the entire system into optics that, at short range, are comparable to our own.

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