INVESTIGATIONS IN EUROPE. 15 



gas for fumigation purposes in the destruction of scale-insect pests of 

 citrus-fruit trees in southern California — work which had been in 

 progress for three years — the writer proceeded to Washington to make 

 final arrangements for his departure on the mission. 



Since the white fly is reported from the United States as being pri- 

 marily an enemy of citrus it was considered that its distribution 

 would be limited to those regions in which citrus trees occur, and nat- 

 urally it followed that these were the places to which travels should be 

 directed. It is well known that citrus trees are grown to a greater 

 or less extent in the semitropical and tropical zones throughout the 

 world. The most tenable supposition is that the}^ originated in 

 southeastern Asia, whence their distribution, either directly or indi- 

 rectly, to those countries in which they are at present to be found. 



In the collections of this bureau are specimens of the citrus white 

 fly which have been taken on orange trees in southern China and in 

 Japan. On his way eastward the writer passed through San Fran- 

 cisco on the day that Mr. George Compere, the weE-known collector 

 of natural enemies of insects for the State of California, was return- 

 ing from the Orient with supposedly valuable introductions. An 

 examination of an orange tree which Mr. Compere had secured in 

 Japan revealed the presence of the citrus white fly, thus corroborat- 

 ing previous records from the Orient. 



The collection of Aleyrodid^ of the late William Maskell of New 

 Zealand is now in the custody of this bureau. In examining type 

 material from this collection of a species named Aleyrodes aurantii 

 Mask., collected on orange m the northwestern Himalayas of India,. 

 Prof. A. L. Quaintance, of this bureau, an authority on Aleyrodidge, 

 decided that this Indian species was none other than the citrus white 

 fly of Florida, Aleyrodes citri. Having the above information at 

 hand it was at once evident that special attention should be devoted 

 to a search of that part of the Orient having a tropical or semi- 

 tropical climate. 



The present known distribution of the citrus white fly throughout 

 the world is shown in figure 1. 



INVESTIGATIONS IN EUHOPE. 



On July 31, 1910, passage was taken on a steamer from New York 

 en route to Spain via Gibraltar. This first stop was made in response 

 to a request from the Minister of Agriculture of Spain that the writer 

 demonstrate before the orange growers of that country the procedure 

 of hydrocyanic-acid gas fumigation in the destruction of scale-insect 

 pests of citrus trees. The orange and lemon trees of Spain are seri- 

 ously affected by several species of scale insects. Satisfactory con- 

 trol of these insects had never yet been accomplished, while many of 

 the orchardists were in despaii' lest their trees should be ruined. 

 62800°— Buh. 120—13 3 



