United States and Canada
This is a ubiquitous species, commonly seen at almost any standing body of water during the summer. It is moderate-sized and stout with a distinct dimorphism between the sexes. Males have large broad brown or black bands in the outer portion of each wing, while the female's wings are less maculated, with three spots, basally, at the nodus and apically, appearing as a smaller version of Twelve-spotted Skimmer (Libellula pulchella). Its face is yellowish-brown initially, but becomes noticeably darker in both sexes. The top of the head is deep brown. The robust thorax is brown, unmarked in front and has two yellowish lateral stripes giving way to white at their upper ends. The wings in the male are as above with a small white spot below the basal dark area in the hindwing. The legs are brown. The abdomen is broad appearing triangu lar in cross-section as it tapers apically in males. The female abdomen is strongly depressed. In both sexes the abdomen is brown with an interrupted white line laterally, appearing as individual stripes. The thorax in mature males becomes darker and the lateral stripes obscured. The most noticeable change, however, is the total envelopment of the male abdomen by a white pruinescence.
Size: Total length: 38-48 mm; abdomen: 23-29 mm; hindwing: 29-35 mm.
Similar Species (US and Canada):
Female Twelve-spotted Skimmer (L. pulchella) is similar to female Common Whitetails (Plathemis lydia), but larger and with yellow dorsolateral stripes on the abdomen that connect together and appear as a single long yellowish stripe along the sides of the abdomen. Female Common Whitetail has yellowish or white diagonal dashes on the side of segments 2-7 that appear as a series of disconnected diagonal stripes or "zig-zag" along the sides of the abdomen. Common Whitetail sometimes has paler brown legs vs black in Twelve-spotted Skimmer. Also the dark patch near the middle of the forewing in Common Whitetail is usually larger in extent relative to the inner dark mark; in Twelve-spotted these spots are about the same extent (although different in shape). The middle dark spot on the forewing of female Common Whitetail starts well inside the nodus and from there it extends inward and backward to a point; on Twelve-spotted Skimmer the middle spot starts near the nodus and extends straight back from there. Finally Common Whitetail has fewer cells along the foreward edge of the forewing from the base to the nodus, around 12-16 in Common Whitetail and around 20-25 in Twelve-spotted Skimmer
Prince Baskettail (Epitheca princeps) is larger with green eyes, a long slender abdomen and it lacks any white in the wings.
Desert Whitetail (P. subornata) has a pale window within the brown wing band at the nodus and has distinct white areas basally.
Eight-spotted Skimmer (L. forensis) has brown wing bands at the nodus that do not reach the pterostigma.
Other similar banded dragonflies like Four-spotted Pennant (Brachymesia gravida) and Band-winged Dragonlet (Erythrodiplax umbrata) lack basal wing markings.
Habitat: Nearly any pool, pond, lake or quiet stream.
Natural History: This is one of the most familiar dragonflies to the casual observer as well as one of the most studied. It has been collected in every county in Arkansas (Harp pers. comm.). The distinct white abdomen of mature males is used in displays to threaten other males. They elevate the abdomen above the rest of the body and fly towards an intruder. Males patrol moderate-sized habitats of 15-30 m around the shores of ponds, lakes and occasionally streams. They will often venture some distance from their breeding sites and may commonly be seen along roadsides and path margins perching on the ground, logs or low vegetation. Adults mature after an average of two weeks, after which they return to bodies of water to breed. Males are aggressive, often stealing females from other males. Mating is quick, occurring as the pair hovers over the water, usually no longer than three seconds. Males will often attempt to guard more than one female as they lay some 1,000 eggs, by tapping the tip of the abdomen to the water in regular intervals. Although this species is widespread, its distribution is limited to the north where more than 1,660 degree days of growth (at a threshold of 5.6o0C ) are afforded. Recently several male specimens dark wingtips were reported from Oregon. All the males I have seen from the region have had clear wingtips.
Distribution: Throughout U.S. and southern Canada.
Source: Abbott, J.C. 2006-2010. OdonataCentral: An online resource for the distribution and identification of Odonata. Available at OdonataCentral.
Edited by Drew Weber (9/24/2015).
