Vol. XI] COLE AND LOIETT—UST OF OREGON DIPTERA 201 



eastward, and this line seems more impassable than the 

 Rocky Mountains. The summers are usually dry some dis- 

 tance west of the Cascades in Oregon. 



The life zones of Oregon have not been worked out in 

 detail like those of California, but the general divisions are 

 known. Dipten* are not so limited in their distribution as 

 are the majority of plants and animals, but they are for the 

 most part characteristic of certain areas and associations. 

 Our material is much too meagre to work out their distribu- 

 tion and we shall not attempt any general conclusions on this 

 point. The coastal strip is usually known as the Canadian 

 or lower Boreal, except around the mouth of the Columbia 

 River where the Transition comes in. Dr. E. C. Van Dyke 

 has recently published a paper on the life zones of Oregon, 

 Washington, and California, and certain of his terms are 

 used in designating the different areas. The name Van- 

 couveran corresponds very closely to the term Transition 

 and is applied to nearly all of Oregon west of the Cascades; 

 the fauna it contains is quite a distinct one. The Willamette 

 valley is pure Vancouveran and Van Dyke believes that it 

 has changed very little since the Tertiary period. A sub- 

 division of this zone along the coast is termed the Pacific 

 Maritime, and is found in western Washington and the 

 northern coast region of California; it is a region of much 

 moisture and many species in the coleoptera tend toward 

 melanism there. There are some evidences of this tendency 

 among the diptera from this region. 



A modified branch of this Vancouveran starts in west cen- 

 tral Oregon and runs south, including the mountains of 

 southern Oregon and northern California ; it follows along 

 the western slope of the Cascades down into the California 

 Sierra, possibly reaching into Lower California. In this 

 Sierran fauna certain species seem to be broken up into rather 

 weak races in the chaos of the Klamath Mountains. Above 

 the Sierran we find the Canadian zone, which is not very ex- 

 tensive in Oregon. The great Upper Sonoran area of eastern 

 Washington pushes down in a wedge to the center of 

 Oregon, nearly connecting with the Upper Sonoran coming 

 up through Nevada from Mexico; here we find the Great 

 Basin fauna. 



