Species heterodon Garrison, 1994 [Erpetogomphus]
This western species is most similar to Yellow-legged Ringtail (E. crotalinus), but is relatively well marked with dark stripes on the thorax and the outer surfaces of the tibiae are black, not yellow. The face and occiput are pale green. The latter has only a slight medial swelling. The thorax is pale green with a brown middorsal stripe widening anteriorly. There is an abbreviated antehumeral stripe free at both ends. The humeral stripe is narrow, becoming more so at its lower end. The mid- and third lateral stripes are only thinly visible at their lower and upper ends. The femora are pale green with the outer surfaces and tibiae black. The wings are clear wi th a light brown pterostigma. The abdomen is pale green with a dark brown or black dorsolateral stripe interrupted anteriorly on segments 3-7. Segments 8-10 are predominantly orange-yellow with a black dorsolateral stripe. The caudal appendages in the male are yellowish and strongly angulated.
Total length: 50-53 mm; abdomen: 37-40 mm; hindwing: 33-36 mm.
The thoracic stripes on Eastern Ringtail (E. designatus ) are more well-developed, segments 1-2 are yellow dorsally, segment 8 lacks a dark stripe dorsolaterally and there is a wash of yellow in the wings basally. Arizona Snaketail (O. arizonicus ) lacks abdominal rings.
Higher altitude rivers and streams with swift current and rocky or cobble bottoms.
I have seen this species with Serpent Ringtail (E. lampropeltis ) in southwestern New Mexico and it has been reported flying with Yellow-legged Ringtail in Rio Pacheco, in the Mexican state of Chihuahua. Females lay eggs as do most other species in this group, by hovering over the water and tapping the abdomen to the water's surface. Males often perch on rocks where they face the stream.
Southwestern U.S. and Chihuahua, Mexico.