614 PROOEEDTNOS OF THE NATIONAL MUSEUM. vol.52. 



this species, excepting an exuvia, possibly of this species, found on 

 McKinney Lakes, 7,000 feet altitude. Palmata certainly is not 

 normally as common above 6,000 feet as below that height. 



9. SOMATOCHLORA SEMICIRCULARIS (Selys). 



Several were caught on sedgy sloughs along Squaw Creek and 

 Truckee River, This is the lowest elevation at which I took this 

 species in this region. In central Oregon (Bend) it is abundant at 

 4,000 feet, in Washington (Bumping Lake) at 3,500 feet, and in 

 British Colmnbia at sea level. 



10. LIBELLULA PULCHELLA Drury. 



Two were seen on Squaw Creek. This is the highest record for 

 this species in this region. 



11. LIBELLULA QUADRIMACULATA Linnaeus. 



Abundant over all marshes above 5,000 feet. 



12. SYMPETRUM RUBICUNDIILUM DECISUM (Hagen). 



This brown faced species was the most abundant dragonfly f>n 

 Squaw Creek. 



13. SYMPETRUM PALLIPES (Hagen). 



Emerging in numbers from grassy sloughs along Squaw Creek. 



14. SYMPETRUM SCOTICUM (Donovan). 



Occasional in Squaw Creek valley. 



LAKE TAHOE, CALIFORNIA AND NEVADA. 



This lake, 23 miles long by 10 broad, is surrounded by mountains, 

 the lower slopes of those on the west shore covered by green pines, 

 those of the east shore brown and barren. Its entire shore line, 

 except for sand along the south shore and some bordering cliffs, is 

 a clean pebble beach. Its water is marvelously clear. Fish are 

 easily seen at a depth of 20 feet and every scratch in the paint on 

 the keel of the lake steamer is so distinct that the boat gives one 

 the idea of floating in the air. This lake is so deep that it does not 

 freeze in winter. Its elevation is 6,225 feet. 



Because of this unusual purity of the water and lack of mud on 

 the beaches and bottom there is almost an entire absence of large 

 aquatic vegetable life. Consequently aU other forms of life based 

 on this are in scanty numbers or entirely absent. 



In three days collecting I saw only three species of dragonflies on 

 the lake. Argia vivida Hagen occurred in a grassy inlet at McKin- 

 ney. Aeshna interrupta nevadensis Walker M^as common but 

 probably bred in the small lakes on the mountains about, and through 

 its great propensity for wandering came to hunt along the Tahoe 

 shores. Opliiogomijihus morrisoni Selys was probably the only 

 species actually spending its nymphal existence in the lake water. 

 A single male which flew aboard the steamer in Emerald Bay is my 

 only information on tliis species. 



