Species eutainia Calvert, 1905 [Erpetogomphus]
Syn Erpetogomphus diadophis Calvert, 1905
This species is found in central Texas, around Laredo, and in northern and central Mexico. It is our smallest ringtail and has a distinctive blue face and blue dorsally on the thorax and basal abdominal segments. The occiput is slightly swollen medially. The thorax is blue dorsally and green laterally with well-marked brown middorsal and lateral stripes; the former widening toward the collar. The antehumeral stripe is linear and free at its upper end and the humeral stripe is long and complete. The mid- and third lateral stripes are present and well-developed. The femora are dark brown to black, except for pale yellow areas midventrally. The tibiae are black. The wngs are clear with black pterostigmas. The abdomen is pale bluish-green with a dorsolateral interrupted brown stripe on segments 3-6 to appearing as basal and distal dark rings and white medial rings on each segment . Segment 7 is pale bluish-green proximally and orange bro wn distally. Segments 8-10 are reddish-brown in the males and darker in females.
Total length: 47-51 mm; abdomen: 29-33 mm; hindwing: 23-28 mm.
Other similar species of ringtails and clubtails have pale rings basally on the segments of the abdomen, not in the middle as in Blue-faced Ringtail. This our only clubtail that has blue on the face and thorax.
Small rivulets and streams of central Texas, with swift current and cobble bottoms. A disjunct population is restricted to the San Marcos and Guadalupe Rivers.
This species is found perching on bushes and grasses adjacent to streams they patrol. It has a very unusal flight pattern for a clubtail, almost appearing more like a damselfly, making only small movements from one perch to the next. This species has only been found in Caldwell. Gonzales and Webb Counties within Texas. It has a long flight season and can be quite common along the sho re lines of both the San Marcos and Guadalupe Rivers where it flys with Eastern Ringtail (E. designatus ) as well as a number of other clubtail species.
San Marcos and Guadalupe Rivers of Central Texas south through Mexico to Costa Rica.