KUBHH 



UNITED STATES DEPARTMENT OF AGRICULTURE 

 BULLETIN No. 903 



Contribution from the Bureau of En tomology 

 L. O. HOWARD, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



April 22, 1921 



THE 

 GRAPE PHYLLOXERA IN CALIFORNIA 



By 



W. M. DAVIDSON, Scientific Assistant, and 



R. L. NOUGARET, Entomological Assistant, 



Deciduous Fruit Insect Investigations 



CONTENTS 



California History 



Accidental and Natural Spread .... 



Distribution of Phylloxera in California . 



Vineyard Destruction 



Nomenclature and Synonymy of the 

 Grape Phylloxera 



Biology of the Grape Phylloxera in Cali- 

 fornia 



The Radicicole 



Page 

 The Nymph and Winged Form .... 73 

 Nymphicals or Intermediate Forms . . 82 



The Sexual Forms 90 



The Gallicole and its Relation to Cali- 

 fornia Conditions 95 



Effects of Water and Heat on Phylloxera . 98 



Diffusion of Phylloxera 100 



Summary 122 



Literature Cited 127 



WASHINGTON 



GOVERNMENT PRINTING OFFICE 



1921 



