44 THE REPORT OF THE No. 1^ 



climatic changes, and are limited in their distribution by the isothermal linea 

 or by the extent of rainfall. Thus, a desert may prove impassable for one 

 species, while another may be equally unable to surmount the barrier pre- 

 sented by a low swampy tract, a high mountain range or a great plateau. 

 The valley of a large river, with its gradual slope and protected nooks, forms 

 a natural highway for the passage of migrating or spreading species. 



Within the Great Basin of North America, certain problems of insect dis- 

 tribution are presented in almost perfect purity. In these desolate areas 

 ai( fcpots rarely trodden by the foot of man, still supporting the life that has 

 been theirs since the time when the valleys were filled with lakes that have 

 left their tide-marks and old beach lines hundreds of feet up the sides of me 

 Wasatch and the Sierra Nevada ; inland seas of fresh water, gradually dwind- 

 ling away as the result of widespread climatic changes, and now represented 

 only by the few meagre salt and bitter lakes that mark the bottom of the an- 

 cient bed. Even these remnants are in danger of disappearance through 

 the loss of their tributaries, diverted for irrigation, so that if we are to study 

 the insects peculiar to their borders the work should not be delayed. 



The Great Basin lies between the Wasatch and the Sierra Nevada. It 

 includes the western part of Utah, nearly all of Nevada, a great part of east- 

 ern and southern California, extending a short distance down the Peninsula. 

 It also takes in a portion of southern Oregon, and small sections of Idaho and 

 Wyoming. Though termed the Basin, it is chiefly high plateau, fringed by 

 still higher mountains, whose outer slopes drain into the Colorado and the Co- 

 lumbia, excepting along the western edge where the surplus rainfall is 

 gathered up by the Sacremento and other rivers that discharge more directly 

 into the Pacific Ocean. The moisture which falls within tfie limits of the 

 Great Basin, however, can escape only in one way, namely by evaporation. 

 None of the streams rising there ever break through the rim nor reach the 

 ocean. The rivers either waste away on the vast deserts or empiy their floods 

 'uto shallow lakes that act as evaporating pans, precipitating the solid mat- 

 ters and returning the rest to the air again. As a consequence of this con- 

 tinual concentrating of the fluids, the waters of the lakes are nearly all strong- 

 ly alkaline or saline, often so bitter as to be useless for drink. The shores 

 are incrusted with salt and soda, sometimes the deposits are several inches in 

 thickness. These beaches, in spite of their forbidding appearance, support 

 u life peculiar to themselves — they are inhabited by an assemblage of insects 

 fitted for just such conditions, and existing nowhere else. 



The lakes are separated by immense tracts of desert — black volcanic rock, 

 old hard-baked mud flats or wide valleys of sr»nd, according to ih'^ ^orr-p'? that 

 have been at work in the making of the land. Much of the valley country 

 is in the neighborhood of five thousand feet above the sea, but it falls off to the 

 southwest where it occasionally sinks ^e-^'^^ral hutidred. fct below the level of 

 the ocean. In the northern part, the climate is moderate, in the southwest 

 it is extremely hot, but certain features are common to the district as a 

 whole — the air is very dry and the rainfall scanty, so there is a constant, 

 though not regular, dwindling of the water bodies. The plant life is 

 essentially that of the desert except on the higher mountain ranges where 

 the trees occasionally reach a profusion of growth which we may call forest. 



It is, however, with the insects that we are mostly concerned, and of the 

 insects we are best acquainted with the Coleoptera. Several types are quite 

 characteristic of the Basin, hardly occurring outside of it, or at most barely 

 passing the borders. In this category, may be mentioned Cicindela echo, a 

 fine tiger beetle; Cicindela tenuicincta : Tanarthrus salicola and its allies, 

 small species frequenting the borders of alkaline lakes and ponds ; three hairy 



