342 PROCEEDINan OF THE yATIO^\iL MUSEUM. vol.49. 



flight k) a near-by bush the couple would rest in copulation for many 

 minutes. The male did not accompany the female during oviposi- 

 tion. The latter would rest on a stone in a riifle and every few sec- 

 onds make a short flight, striking the tip of her abdomen on the sur- 

 face of the water just once, when she would rest for a few seconds on 

 a stone and repeat the process. These short flights were repeated 

 five or six times in succession. By August 1 many individuals 

 showed age in the frayed wings, the olive coloration, and in their 

 difficulty in standing. Frequently when one would attempt to aUght 

 on a stone it would fall over on its side or tumble on its head. During 

 the first part of their season they were most abundant on the gravel 

 bars, but during the oviposition period they were most a])undiHit 

 about the riffles. 



Figures 190 and 191 show dorsal and lateral views of the nymph 

 of severus. Figures 192, 193, and 194 show details of the nymph of 

 severus and figures 195, 196, and 197 details of that of occidentis. 



18. GOMPHUS, SP. 



I have several immature nymphs of Gomj>hus which I found in 

 the Sunnyside Canal in 1912. 



On November 1 of each year the headgates of the Sunnyside Canal 

 are closed and remain closed until April 1 the following spring. On 

 * November 14, 1912, in the mud puddles in the bottom of the canal 36 

 miles below the headgates, I gathered 10 immature gomphine larvae. 

 Four of these were undoubtedly OpMogomph'ns severus, while the other 

 6 are undescribed nymphs belonging in the Stylurus subgenus of 

 Gomj^Jius. In going over the literature of gomphine nymphs I find 

 that an attempt to assign these a specific identity would be largely 

 a matter of shuffling the suppositions of the various students of 

 Gomphus. I think that on two dift'erent occasions I have seen 

 imago Gomjihus on the Yakima River; if so, it is a species difficult to 

 approach. 



The six nymphs vary from 7.5 to 15 mm. in length. The abdo- 

 men of the longest specimen is 10 mm. long and 4 broad. Segment 

 9 about one and one-haK times as long as 8. A longitudinal 

 dorsal groove with a depressed triangular spine on middle of apical 

 edge of segment 9. Segments 6-9 with lateral spines. Spines on 

 segment 9 one-half as long as the cylindric segment 10. Labium one 

 and one-fourth times as long as broad. Anterior edge of mentum 

 almost a straight line, bearing 16-18 short, yellow, bristle-like scales. 

 Lateral lobes with large hook curving in sharply at almost a right 

 angle and bearing along its concave inner side 3 to 4 blunt teeth. 

 Outer movable hook weU developed. Antennae with third segment 

 one and one-half times as long as first two and with fourth segment a 

 short truncated cone curving upward so that the circular end 

 surface is horizontal. 



