574 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



GOMPHUS DONNERI, nymph. 



A light colored, very delicato and thin skimied exuvia, its surface 

 thinly covered with very short, spiny hairs. General shape interme- 

 diate, neither broad nor slender. It is distinguished from other 

 GompTius nymphs by the following characters : 



Mentum of labium slightly longer than wide, its posterior edge two- 

 thirds width of anterior edge, its sides slightly sinuate. Its middle 

 lobe convex, with a fringe of about 30 bristlehke scales. Lateral 

 lobes broad at base, tapering regularly to a crescentic tip, the inner 

 margin of which bears about 7 low rounded teeth between which and 

 the base of the lobe are other smaller teeth. Well developed burrow- 

 ing hooks on both the first and second tibiae. Wing pads reaching to 

 or beyond apex of third segment. Abdomen lanceolate, slightly 

 contracted at base of ninth segment, well arched, no sign of a dorsal 

 groove, but apex of segments 2-7 with a low rounded middorsal 

 tubercle terminating caudad in a minute middorsal tooth on apex of 

 segments 2-7, larger on segments 8 and 9. Lateral hooks on seg- 

 ments 6-9, those on 9 one-fourth to one-third the length of segment 

 10. Segments 2-8 subequal in length; segment 9 one and a half 

 times as long as 8; segment 10 as long as broad and two-thirds length 

 of 8. Appendages as long as segment 10. (See figs. 316 and 324- 

 325.) 



Length, 29 mm.; abdomen, 20; hind femur, 6. Width of head, 

 5 mm,; abdomen, 6.5. 



Described from 2 male and 1 female exuvia and 6 fragmentary 

 exuviae collected on the west end of Domier Lake, California, July 

 24, 1914. These were found in the trash of the wave line on the 

 sandy beaches along the northwest point of the lake. 



14. NOTES ON OCTOGOMPHUS SPEGULARIS AND ITS NYMPH. 



Tliis graceful dragonfly appears most commonly and m greatest 

 abundance on the perennial torrents of the coast mountauis of 

 California. These are streams which never freeze, not even carrying 

 snow water, and which vary in size from trickling spring streams to 

 roaring torrents. The coast mountains are heavily timbered with 

 redwoods and fir on their ocean slopes, but on their eastern side are 

 covered with dense growths of brush except in the deep V-shaped 

 gulches where are found mixtm-es of redwoods, oaks, alders, and 

 bays. It is in the rushing streams which hurry down through the 

 dense shade of these steep and narrow gorges that Octogomphus is 

 found. Here it is accompanied by only three other dragonflies. 

 Cordulegaster dorsalis and Aeshna walkeri breed with it in the stream 

 and Argia vivida occupies the springs along the lower courses of the 

 torrents. Both Octogomphus and Cordulegaster are confined to the 

 torrential headwaters of the stream but Aeshna walkeri and Argia 



