McLachlan in Selys, 1873
Species borealis McLachlan in Selys, 1873 [Progomphus]
Syn? Progomphus meridionalis Hagen, 1885
This is the o nly western sanddragon in North America. It is easily distinguished from the eastern species by its larger size and the absence of a midlateral stripe. It is dull grayish-green. The thorax is yellow in front and grayish-green laterally. The antehumeral stripe so angled at its upper end that it nearly becomes confluent with the middorsal stripe. It is confluent with the humeral stripe at its lower end and again at about 2/3 its length, but the latter is free at its upper end. The midlateral stripe is entirely absent above the spiracle. The third lateral stripe is present and well-developed. The wings are clear with only a wash of brown at their extreme bases. The abdomen is largely black, ringed with yellow. Segments 8-10 are expanded slightly laterally and the cerci are yellow. The male epiproct is black.
Total length: 56-62 mm; abdomen: 42-45 mm; hindwing: 33-36 mm.
Sandragons are readily identifiable because of the bright yellow cerci. The smaller Common Sanddragon (P. obscurus ) has two dark lateral thoracic stripes and more brown basally in the wings.
Shallow desert, sandy-bottomed streams.
I have taken this species in Palo Duro Canyon State Park, Texas, on the Prairie Dog Town Fork of the Red River. This is apparently the eastern-most locality for this species and it was flying with Common Sanddragon. Gray Sanddragon flies along stream margins with heavy vegetation occasionally resting on exposed sand banks in relative shade, where it can be inconspicuous. This species is often seen with its abdomen directed upward, in an obelisk position, so as to almost appear like it is standing on its head. Females lay eggs while flying erratically, low over the water and tapping their abdomens to the surface. Both sexes of this species have a straight smooth, erect spine middorsally at the rear edge of the first abdominal tergite that is apparently a persistent larval dorsal hook.
Southwestern U.S. and Mexico.