Species verticalis (Say, 1839) [Agrion]
Males are dark with a narrow green antehumeral stripe and a yellow-green thorax laterally. The antehumeral stripe is often narrowed at about 2/3 its le ngth. The abdomen is largely black with segments 8-9 bright blue dorsally. The dorsoapical projection on segment 10 is blunt and forked for half its length. It projects more dorsally than posteriorly, not extending beyond the hind margin of segment 10. The cerci slant downward in lateral view, terminating to an acute apex. The paraprocts have an abrupt dorsobasal process followed by lower posteriorly projecting process that curves upward. The less common andromorphic female has postocular spots larger and confluent with the rear of the head. The blue on abdominal segments 8-9 is variable and often restricted to the apical half of the segment. The more common gynomorphic females are orange marked with black. The abdomen is largely black dorsally, especially from segments 4-10. Both color forms become dark and heavily pruinose with age. The mesostigmal plates are distinctly triangular, generally with a prominent posterior ridge or flange. There is a well-developed vulvar spine on abdomin al segment 8.
Total length: 20-33 mm; abdomen: 15-26 mm; hindwing: 11-19 mm.
Male Eastern Forktails most closely resemble Mexican (I. demorsa ) and Western (I. perparva ) Forktails. The dorsoapical projection in male Eastern Forktails, however, is reduced while in Mexican and Western Forktails it is prominent and readily visible in the hand. Only Mexican Forktail overlaps slightly with Eastern Forktail's geographic range.
Ponds, lakes, slow moving streams and marshes.
One of the most common damselflies in the northeastern United States, and throughout Oklahoma, this species is uncommon south of the Red River. Eastern Forktail has been variously reported from Louisiana, but the validity of these records remains questionable. There are no modern records in the state one study did not rule out its occurrence in the northern part of the state. In much of its range it is one of the first damselflies seen in the spring and last seen in the fall. Various aspects of this ubiquitous species have been well studied. Among these it has been suggested that strong winds may be the principal ca use of its dispersal. Another study found that mating took place as early as four days after emergence and that egg laying began a few hours after mating. The well-documented behavior of Eastern Forktail females flexing the abdomen ventrally and rapidly beating their wings was determined to be a successful threat display, warding off intruders. It has been shown that food intake is an important determinant of the number of eggs laid in Eastern Forktail and that adult body size is relatively unimportant. Failure to find food on any one day has consequences not only for clutches laid the next day, but also for subsequent clutches. Unlike most damselflies, Eastern Forktail females tend to be monogamous, mating only once. A female may fertilize over a thousand eggs using the sperm from a single-male encounter without a drop in fertility.
Eastern U.S from Georgia to Newfoundland and west to Montana and New Mexico.