Tuesday, July 2, 2013

Common Whitetail: The Road to Pruinosity

One can hardly write about dragonflies without mentioning pruinosity, as I have done last July when blogging about Powdered Dancers last July. This year Erika’s garden has been full of Common Whitetails. We have counted up to 13 at once as the dragonflies basked on the warm side of our house.

Male Common Whitetails’ abdomens become Pruinose. Pruinosity is a powdery pigment “bloom on odonates that exudes from the cuticle and turns it light blue, gray, or white…” (Paulson). Pruinosity often reflects ultra-violet light. Pruinosity is more prominent on mature individuals and more often on males. The first three photos show Common Whitetails in various stages of becoming pruinescent. The last photo shows an unpruinescent female whitetail—similar to the female Twelve-spotted Skimmer (which has a yellow striped, rather than spotted, abdomen.

Common Whitetails make use of pruinosity for species and sex recognition, for making territorial displays, and, perhaps, to cool their bodies by reflecting solar radiation.

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