156 DRAGONFLIES OF NORTH AMERICA 
are blackish. Occiput small, pale, clothed and fringed with tawny hairs. Stripes 
of the front of the thorax abbreviated and narrowed to a point below, and 
strongly divergent. Legs black. Wings hyaline; costa yellow; stigma black. 
The pale dorsal crossbands of the abdominal segments are dilated forward at the 
sides and incised by the black of the mid dorsal line on segments 2 to 6, and on 
2 to 4 there is an additional side spot below. The crossband on 7 is broader; on 
8, narrower and narrowly divided in the middle line; and on 9, reduced to a pair 
of widely separated pale dashes in the midst of the black; 10 and appendages 
black. 
116. Cordulegaster dorsalis Hagen 
Hag. ’57, p. 347: Mtk. Cat. p. 76: Kndy. 717, p. 515 (figs.): Smn. ’26, p. 26: 
Ckll. ’19, p. 22. 
Length 76 mm. Expanse 94 mm. Pacific Coast, Alaska to Calif. 
A fine big black west-coast species with thorax conspicuously striped and 
abdomen dorsally spotted. Face yellow with a faint wash of brown above across 
the upper margin; clypeus and labral border brown. Occiput brown, with 
marginal fringe of tawny hairs. Pale stripes of the front of the thorax rather 
broad, regular, strongly divergent downward. Those of the sides broad and 
regular. Legs black, brownish at base. Wings hyaline with brown stigma. Pale 
spots of the abdomen more or less saddle-shaped on segments 2 to 9, diminishing 
in size to rearward, bilobed behind on most of the segments; 10 mostly black. 
Appendages black. 
Kennedy, who studied this species in the coast Mountains of Califor- 
nia, (17, p. 516) observes, 
Cordulegaster dorsalis is found usually on those swift mountain torrents which 
do not freeze in the winter time. It is found in the swift upper reaches of all the 
perennial streams. It does not occur on the lower reaches of these same streams 
after they have emerged onto the level floors of the valley, and have lost their 
swiftness to become warm and muddy. In the steep and narrow mountain gorges 
where the rushing torrents pour down through the shade of the redwoods and 
alders, this dragonfly adds a note of mystery to the scene; for the individuals 
with their strange ophidian coloration glide noiselessly up stream and down, 
never showing that curiosity towards strangers or unusual surroundings which 
is exhibited by the Libellulines of the sunny valleys, but always moving straight 
ahead as though drawn irresistibly onward. Only males are common on the 
streams, the females seldom resorting to the water except to oviposit. 
The males, as indicated above, fly on the longest beats I have observed for 
any dragonfly, for they fly continuously up stream and down, until they come 
to the head of the stream or to the slow water below, or until some unusual 
obstruction turns them aside, when they face about and fly as steadily in the 
opposite direction. The course is usually a foot or two above the surface of the 
stream and goes through dense shade and any loose brush or foliage which may 
hang over the water. Because of this habit of flying in long beats this dragonfly 
is not easily taken, as the collector has but a single chance at each individual. 
In the streams of the Coast Mountains of California, whereI havehad oppor- 
tunities to observe the habits of Cordulegaster most, it shows a marked upstream 
migration of the imagoes. The eggs are laid in the shallow water along the edges 
