UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 903 
Contribution from the Bureau of Entomology 
L. O. HOWARD, Chief 
Washington,D.C. 
PROFESSIONAL PAPER 
April 22, 1921 
THE GRAPE PHYLLOXERA 1 IN CALIFORNIA, 
By W. M. Davidson, Scientific Assistant, and R. L. Nougaret, 2 Entomological 
Assistant, Deciduous Fruit Insect Investigations. 
CONTENTS. 
Page. 
California history 1 
Accidental and natural spread 7 
Distribution of phylloxera in Cali- 
fornia 11 
Vineyard destruction 15 
Nomenclature and synonymy of the 
grape phylloxera 26 
Biology of the grape phylloxera in 
California 27 
The radicicole 44 
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 phyl- 
loxera 98 
Diffusion of phylloxera , 100 
Summary 122 
Literature cited 127 
CALIFORNIA HISTORY. 
EARLY VINE PLANTING IN CALIFORNIA. 
The grape phylloxera is not native to California. It has long 
been recognized as originating in North America, but its native 
habitat is east of the Eocky Mountains. The insect has not established 
itself upon the native vine of California (Vitis calif omica) in the 
Avild state, whereas in Arizona it is established on native vines. 
1 Phylloxera viti folia e (Fitch). 
2 Now in charge, Viticulture Service, California Department of Agriculture, Sacramento, 
Calif. 
Note. — In connection with other work in California, the office of Deciduous Fruit 
Insect Investigations, Bureau of Entomology, in cooperation with the Bureau of Plant 
Industry, has been engaged in an investigation of the grape phylloxera during several 
years past, with principal headquarters for the work at Walnut Creek. The work 
inaugurated by E. L. Jenne, upon his death was taken over by S. W. Foster, assisted by 
R.. L. Nougaret. Upon Mr. Foster's leaving the service, the investigation was continued 
by Messrs. Nougaret and Davidson, the latter giving especial attention to biological and 
life-history studies and the former to investigations in the field and to remedial opera- 
tions. The present report deals with the history, injuries, and life history of the insect 
in California. Remedial measures will be made the subject of another publication. It 
has been necessary to omit an extended bibliography of the subject. — A. L. Quaintance, 
Entomologist in Charge of Deciduous Fruit Insect Investigations. 
1900°— 21 1 
