PR H FACE. 



The systematic treatment of the Thysanoptera of California, which 

 is presented in this paper, is the direct outgrowth of an investig-ution 

 of the pear thrips {E^dhTlps pyri Daniel) which was undertaken in the 

 Santa Clara Valley of California during the period from January, 

 1905, to April, 1906. This insect has become a serious fruit-tree pest 

 in the deciduous-fruit sections around the San Francisco Bay. An 

 important phase of the investigation was to learn the insect's distribu- 

 tion and the number of its food plants, both wild and cultivated. In 

 looking for E\itlirip>< 2jy7'! on various plants, naturally man}^ other 

 species of thrips were found, and much of interest learned regarding 

 the life habits of several of them. It is the object of this paper to 

 bring together these various observations and also the results of the 

 more technical part of the work, leaving the economic treatment of 

 the pear thrips for a separate paper. 



The investigation of the pear-thrips problem in the Santa Clara 

 Vallev, as also the collecting of specimens described herein, was made 

 possible by the very liberal attitude of the Santa Clara County board 

 of supervisors, who granted ever3'tliing necessary for a thorough and 

 scientitic study. The very careful and efficient work of the writer's 

 two assistants, Mr. Earl L. Morris and Mr. C. T. Paine, must also be 

 acknowledged. To Prof. Vernon L. Kellogg, professor of entomology 

 in the Leland Stanford Junior Universit}^, the writer wishes to express 

 his gratitude for encouragement, helpful suggestions, and friendly 

 criticism. 



D. M. 



