INVESTIGATIONS IN ETJKOPE. 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 they 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 well-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 Aleyrodidse 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 Aleyrod.es aurantii 
Mask., collected on orange in the northwestern Himalayas of India, 
Prof. A. L. Quaintance, of this bureau, an authority on Aleyrodidse, 
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 EUROPE. 
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 hydro cyanic-acicE 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 despair lest their trees should be ruined. 
62800°— Bull. 120—13 3 
