United States and Canada
The face of the male is pale blue-green, heavily marked with black. There are two small pale blue postocular spots that are generally confluent with a narrow occipital bar. The thorax is green with a black middorsal and humeral stripe. The latter is approximately half the width of the midd orsal stripe. The abdomen is blue-green on the first two segments and part of 3. The remainder of the abdomen is yellow-orange dorsally marked with black. The posterolateral portion of segment 7 and all of 8-9 are blue. Segment 10 is blue with a wide black dorsal stripe. The dorsoapical prominence on segment 10 is conspicuous, but does not extend posteriorly beyond segment 10. The cerci are not forked, but strongly directed downward. The paraprocts are gently upturned or straight with the apices upturned. When viewed dorsally, the female mesostigmal plates each bear a flange extending posteromedially to the anterolateral corner. Andromorphic females are uncommon and nearly identical to males. Gynomorhpic females are orange or tan often with a slight greenish cast to the abdomen. The abdomen is generally similar to the male, but with a black basal triangle and subapical spot on the dorsum of an otherwise pale segment 8. These spots are occasionally narrowly confluent. There is a full-le ngth black stripe on segment 9 and segment 10 bears a dorsal black triangle extending the entire length of the segment.
Size: Total length: 28-35 mm; abdomen: 22-27 mm; hindwing: 14-19 mm.
Similar Species (south-central US): Male Rambur's Forktails (I. ramburii) are similar but the top of abdominal segment 9 is black and in Desert Forktail the entire segment is blue. The humeral stripe in Rambur's Forktail is also slightly wider. Female Desert Forktails typically have larger postocular spots compared to Rambur's Forktail. The gynomorphic form of Rambur's Forktail is is typically brighter orange and has black dorsally on segment 8
Habitat: Alkaline and saline, desert springs, pools, irrigation ditches and canals.
Natural History: Little is known of this species' ecology and behavior, but it is presumably similar to other forktails. It can be quite common around heavily vegetated alkaline and saline lakes.
Distribution: Western U.S. from Nebraska to California south to Texas.
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).
