LETTER OF TRANSMITTAL. 
UnitTep States DEPARTMENT OF AGRICULTURE, 
BurEAU OF ENTOMOLOGY, 
Washington, D. C., March 2, 1911. 
Smr: I have the honor to transmit herewith, for publication as 
Bulletin 92 of the Bureau of Entomology, a manuscript prepared by 
Drs. A. W. Morrill and E. A. Back, dealing with the life history of 
the white flies injurious to citrus trees in Florida. 
The investigation of the citrus white flies in Florida, under the 
general direction of the assistant chief of this bureau, Mr. C. L. Marlatt, 
was begun in 1906, and is now approaching completion. There has 
already been published a bulletin (No. 76) dealing fully with the 
general subject of fumigation with hydrocyanic-acid gas for the white 
fly. A circular (No. 111) has also been issued, giving brief directions 
for winter fumigation. 
The present publication is a general account of the two species of 
white flies which are of special economic importance to the citrus 
grower in Florida. The publication includes the history of these 
insects in the United States, their distribution and food plants, and 
a very detailed study of the habits and life cycle of the two species. 
A great deal of painstaking and minute work has been done, and the 
information secured furnishes an accurate foundation for the develop- 
ing of the best means of control. 
Supplementing this publication, which deals largely with life his- 
tory and habits, it is proposed to publish a bulletin on control by 
sprays, fungi, and other enemies, and to supplement or reissue in 
revised form the bulletin dealing with fumigation. 
Respectfully, 
L. O. Howarp, 
Entomologist and Chief of Bureau. 
Hon. JAMEs WILSON, 
Secretary of Agriculture. 
