NO.2107. DRAGONFLIES, WASHINGTON AND OREGON— KENNEDY. 285 



bordered on each side with intense black. A low lateral keel on 

 segments 1-8 (not conspicuous on segments 7 and 8). A narrow, 

 jogged white stripe dorsad of either lateral keel. The lateral gills 

 are very spoon-shaped and in fresh material variously banded with 

 black. 



Male with the two points on the sternum of segment 9 shghtly 

 longer and more attenuate than in vivida. (See figs. 68-69.) 



Female with the two outer or ventral members of the ovipositor 

 shorter than the dorsal or inner pair. (This is true also in vivida, 

 but only for the immature nymphs.) The genital valves, especially 

 the posterior points, vary greatly in shape. In tliis species they are 

 usually conspicuously toothed, especially on the distal haK of the 

 ventral edge. (See figs. 66-67.) 



Male, a skin collected August 3, 1913, on Satus Creek, Yakima 

 County. (On the same date I collected a male in the act of emerging, 

 but the skin blew into the water, damaging it too much for a type 

 specimen.) Deposited in the United States National Museum. 



Female, collected on Satus Creek, June 29, 1913, reared, emerg- 

 ing between July 2 and 10, while I was in Oregon, during which time 

 the teneral drowned, being badly decayed on my return. Skin and 

 imago deposited in the United States National Museum. 



About 20 specimens, including both skins and nymphs, were col- 

 lected during 1913. The nymphs of this species are not easily found, 

 as they roam over the whole creek bed and so are never numerous 

 in any single place. They are usually found in the roots and brush 

 of the larger pools and under large stones on the riffles. On turning 

 a stone over the nymph is usually on the bottom beneath the stone 

 and hurrying away. This is a noticeable difference between this 

 nymph and that of vivida, which is usually hanging back down from 

 the stone picked out of the water, and very sluggishly arouses to the 

 fact that it should hunt shelter. The agility of the emma nymph per- 

 mits it to live in the swift riffles and contest for existence with the 

 crayfish and stonefly and mayfly nymphs. It is the pnly odonate 

 nymph found in the swift riffles of Satus Creek. 



Emergence, judging from the finding of tenerals, takes place any 

 hour of surdight after the middle of the morning. The nymph usually 

 crawls up on a stone, seldom more than an inch above the water. 

 On August 3, 1913, I found an Argia emerging. It had crawled up 

 on to a smooth pebble Ipng in the middle of a shallow riffle, where 

 I found it at 9.52 in the morning an inch above the surface of the 

 water, with head, thorax, and legs already mthdrawn. It was clasp- 

 ing the head of the skin with its frail feet. It was a grayish cream 

 color. In a minute it moved its legs in a tentative maimer, then 

 quickly crawled up on the stone just in front of the head of the skin, 

 but with the tip of the abdomen still retained in the skin. In a 



