Explanation of Names
Once upon a time, this was the Ten-spot(ted) Skimmer, and formerly appeared in most books under that common name. To make it so, the basal spot of opposite wings was counted as one spot crossing the thorax (and so it appears at a glance, especially when they are flying or seen from a distance). Some authors rationalize it as counting the cloudy white spots on the wings, but that's only good for mature males, and it often doesn't work (there are often only eight white spots, the two at the base of the hind wing either missing or having been rubbed off).
Numbers
One of between about 25 and 30 species. Most are North American.
Identification
Mature males have twelve brown wing spots, as well as eight white wing spots. The basal area of the hind wing is also whitish.
Females and immature males have the twelve brown wing spots but not the white spots. Their abdomens are brown with a yellow stripe along each side.
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Comments from Cliff and Tony, Gayle and Jeanell on the thoracic side stripes, wingtips, stigma, and perching habits of Libellula pulchella vs. Plathemis lydia:
Interesting -- To be honest, I never noticed or paid attention much to the thoracic stripes of these two species. However, I searched through my photos and I did notice a slight difference.
Here is a composite photo of the thorax of each dragonfly. The rear (metepimeral) stripe has a definite bend in lydia, somewhat like a boomerang, whereas in pulchella it is pretty much straight.
… Cliff Bernzweig, 22 November, 2006
I took a look at my images. The anterior thoracic stripe in lydia, both males and females, consists of a long dorsal dash and a separated ventral dot. Can be seen in Cliff's composite image and here:
In pulchella, the anterior stripe is just 1 long dash.
… Tony Thomas, 22 November, 2006
Good eye - Didn't notice that either. It looks as if the anterior stripe extends across the suture dividing the pterothorax and the prothorax, forming a pale dot on the prothorax, whereas in pulchella the stripe stops at that suture.
… Cliff Bernzweig, 22 November, 2006
Our 2 cents -- MOST female L. pulchella have a relatively narrow dark area at the wingtip, exposing most of the stigma. MOST female Plathemis lydia have a wider dark area at the wingtip, covering most of the stigma. The trailing edge of the hind wing appears straighter in L. pulchella. We don't remember ever seeing a P. lydia perched more than 3 ft. above the ground. This specimen appears to be on a higher perch.
For scans of a live female P. lydia check
here.
For scans of a live female L. pulchella check
here.
For highest resolution, after opening the image, click on "get original uploaded photo" beneath the image.
… Gayle and Jeanell Strickland, 22 November, 2006
Range
Extreme southern Canada; all 48 contiguous states; range continues across the border into Mexico.
Migratory.
Habitat
Ponds and lakes; sometimes bogs or slow-moving streams.
Season
Primarily a summer species.
Life Cycle
Newly emerged males have a color pattern similar to females. As they age they get pruinose but the original pattern can still be seen through the blue.They get even more pruinose blue with age and the spots get powdery blue also. The first in the series would be called teneral - brand new. The second might be referred to as immature, but it is still an adult. True immatures are nymphs in the water.
