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Common Whitetail



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Plathemis lydia

Drury, 1773


Order Odonata
Suborder Anisoptera
Superfamily Libelluloidea
Family Libellulidae
Genus Plathemis
Species lydia (Drury, 1773) [Libellula]


Identification

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

Female Twelve-spotted Skimmer (L. pulchella ) is similar, but larger and with yellow dorsolateral stripes on the abdomen. 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.

Discussion

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.