U. S. D. A., B. E. Bui. 99, Part I. D. F. I. I., March 6, 1911. 
PAPERS ON INSECTS INJURIOUS TO CITRUS AND OTHER SUBTROPICAL 
FRUITS. 
THE ORANGE THRIPS: A REPORT OF PROGRESS FOR 
THE YEARS 1909 AND 1910. 
By P. R. Jones and J. R. HoRTON, a 
Agents and Experts, Deciduous Fruit Insect Investigations. 
INTRODUCTION. 
The orange thrips (Euthrips citri Moulton), a small, yellow, active 
insect belonging to the order Thysanoptera (popularly known as 
thrips) , scars the fruit and curls and distorts the leaves of the orange. 
At the present time its control constitutes the chief insect prob- 
lem confronting the citrus growers of the San Joaquin Valley 
orange belt of California, which winds along the Sierra Nevada foot- 
hills, from east of Fresno to south of Delano. This insect, the work 
of which was first noticed 15 or 16 years ago, has increased in num- 
bers with the growth of the citrus industry and recently has assumed 
serious economic importance. 
At the urgent request of a number of orange growers of Tulare 
County, an investigation of the insect was begun the latter part of 
April, 1909. The present paper is a preliminary report of the results 
obtained during the seasons 1909 and 1910. 
The writers wish to acknowledge the financial assistance of the 
Tulare County board of supervisors, the Lindsay Citrus Growers' 
Protective League, and the Tulare County Fruit Exchange; they 
desire to acknowledge the kindness of Messrs. P. M. Baier, Harry 
Postlethwaite, and R. H. Shoemaker in allowing the Bureau of Ento- 
a The investigation of the orange thrips by members of the force engaged in 
studies of deciduous-fruit insects appeared desirable, because these men were 
familiar with a closely related species — the pear thrips — which is very destruc- 
ti to prunes, pears, cherries, etc., in the San Francisco Bay region. However, 
in order to keep together the articles dealing with insects damaging citrus and 
other subtropical fruits, the present paper is published in a series of articles 
dealing with insects of that class. — A. L. Quaintance, in Charge of Deciduous 
Fruit Insect Investigations. 
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