INSECTS OF REVERSED BEHAVIOR. 39! 



The first of these that was found is sEshtia nercadensis Walker 

 of the Sierra upland of central California. 1 This is a large, pond 

 and shallow lake dragonfly that lives at elevations of 5,000 

 to 9,000 feet. It is known only from the southern Sierra Moun- 

 tains. It has been recorded from Walker Lake, Mono Co., 

 California, at 7,700 feet elevation, Hardin Lake, Tuolumne Co., 

 at 7-775 icet elevation and from Elizabeth Lake, Yosemite 

 National Park at the great altitude of 9,000 feet. The writer 

 found it at it- optimum development in shallow, weed-tilled 

 lakes on the divide between Lake Tahoe and the Rubicon Ri\cr 

 (Calif, ulien- .it an elevation of 7,000 feet it dominated the 

 Hibalpine dragonfly life. Here in an open, meadow-like moun- 

 t.iin pass, fairly level for about two miles, lie four shallow la! 

 t\\o tli.uinu into Lake Tahoe and the desert drainage, while the 

 a her t\\o empty into the Rubicon River and the Pacific drain 

 ( >n both -ides rise granite crags for a thousand feet abo\ e the 

 lake-, their lower parts green with lirs, while their gray upper 

 >lope~ are blotched white with fields of snow. Three of the lake- 

 are <. \ered with yellow flowered pond lilies and are frin-<>| 

 wit: ' s among clumps of silver gray willows. 11 



shallo\\ l.ikes are warm because of the black peat bottom and 

 Ion.; horns of sunshine. They support great numbers of a t'ew 

 specie- .l HIM . t-- -such as are able to withstand the long winter- 

 aml culd in-lit- .it tin- elevation, as this is a -nbalpine situation 

 with niyjulv temperatures at or near freezing. Eight other 

 species <>i di.c.-uillies are common here. These are northern 

 term- th.it occur in the mountains of Oregon at 3,000 4,000 

 I'eet elex.ition and in British Columbia at sea level. 



The habitat ot nccadensis appears to be entirely above that 

 ill other species of North American /Eshnas. It appear.- as 

 st ra\ cd individual:- at 4,500 feet but does not appear in nnnil 

 until an ele\ation of 6,000-7,000 feet is reached, l-p.m here up 

 to 9.000 feet it appears at its optimum de\ elopnient . No other 

 .1 -Ima- ha\e been found regularly at the-e higher altitudes. 

 1 tom about 4.500 feet down to sea level, ln>we\er. .K-hna- are 

 a con-tant element of the North American ((donate fauna. 

 T \\cnty or more lowland species have been described from north 

 of Mexico while there are actually seven or eight species living 



1 Kennedy. l'r.>L. U, -S. -V.J/. Mus.. \'ol. 5-', pp. 483-035. 



