J9g CALIFORXIA ACADEMY OF SCIEXCES [Pkoc. 4th Se*. 



of the Aldrich Catalogue, and several European species are 

 included which were not known from North America at that 

 time. The rediscovery of many old species has been more 

 gratifying to us than the discovery of a number of unde- 

 scribed ones. 



Most of the collecting was done in the Hood River 

 Valley, Forest Grove, the Mt. Jefferson region, and the 

 section around Corvallis. Our collecting time has been short, 

 as work on the list was commenced in the early summer of 

 1917, and most of the work had to be done in spare time. 

 Naturally, we spent most of the limited time at our disposal 

 in collecting specimens that were of especial interest to us; 

 as a consequence, many of the families are not adequately 

 represented. The diptera collection at the Oregon Agri- 

 cultural College formed a nucleus on which to build ; the 

 earliest records are a little previous to 1900, and some speci- 

 mens were collected in 1906 and 1907 by Mr. J. C. Brid- 

 well. No extensive collections of Oregon diptera are known 

 to us outside of those we have assembled. 



Space does not permit of a detailed comparison of this 

 list with others, such as the New Jersey and Florida lists 

 written by C. W. Johnson, but such a comparison is inter- 

 esting to the student of distribution. This preliminary paper 

 lists 953 species from Oregon; Johnson gives 845 species for 

 Florida and 1662 species for New Jersey. Certain families 

 of the diptera are well represented in Oregon, although only- 

 one group, the Syrphidae, has been collected extensively. In 

 the Asilidae only one species is common to Oregon and 

 Florida and there is no species common to Oregon and 

 New Jersey. Each region has a distinct dipterous fauna, 

 with a sprinkling of widely distributed forms, some of which 

 are boreal and some cosmopolitan. 



PHYSICAL FEATURES OF OREGON 

 The state of Oregon has an area of 95,607 square miles. 

 In altitude, it ranges from sea level to over 10,000 feet on 

 some of the mountain peaks. The annual rainfall ranges 

 from 70 inches or more on the coast to nine inches in parts 

 of the eastern plains region. 



The Cascade Range has a great effect on the climate and 

 faunal distribution; the Coast Range has less influence, being 



