336 ANNUAL lIErullTb OF DErAKTMENT OF AeiKlCULTUllE. 



fly and the stable fly were capable of carrying the disease for short 

 periods under certain conditions, this suggestin*^ the desirability of 

 securing more ihita on this subject, and especially to determine if 

 some insect might be responsible for the appearance of cholera at 

 various points sometimes far removed from known cases of the 

 disease. Kxj)eriments were carried out with the house fly, stable fly, 

 and Simuliuni. The first two species gave positi\e transmissions in 

 a number of instances, the results on the whole agreeing closely with 

 tiiose previously obtained by the Bureau of Animal Industry. 

 Studies were also made of the insect fauna of hog excrement and 

 the Aarious ways in Avhich insects are associated with hogs. These 

 should aid in epidemiological studies of the disease. 



Insects affecting the health of man. — The work of the bureau 

 laboratory at Mound, La., was materially narrowed during the war 

 ])eriod by service in the Army on the part of the force at that station. 

 This condition continued throughout the greater part of the fiscal 

 year 1920. Two definite lines of work were continued having for 

 their objective further definite information on the biology of malaria 

 mosquitoes and the practical antimosquito measures that apply in the 

 prevention of malaria on plantations and farms. These lines con- 

 sisted of the determination of the relative densit}^ or numbers of 

 Anopheles in and about plantation houses under varying environ- 

 mental conditions and the relative capacity of various classes of sur- 

 face water in Anopheles production, together with the effect of 

 such production upon the adult densit3^ During the year the United 

 States Bureau of Fisheries completed cooperative studies on the mos- 

 quito-eating fish of the region under observation. 



Former lines of work upon the effect of malaria on crop production 

 and agricultural development, upon the relative eflicienc}^ of the 

 various species of American Anopheles mosquitoes to act as the hosts 

 of the malaria parasites, upon the breeding requirements of Anoph- 

 eles larvae, upon the density and food requirements of adults for 

 malaria transmission, and upon regional distribution of Anopheles 

 in respect to topography, agricultural operations, and agricultural 

 development have not been resumed through shortage of funds. 



Malaria, the prevention of which is entirely a biological problem 

 based upon the control of Anopheles mosquitoes, costs the United 

 States, and particularly the South, millions of dollars annually in 

 loss on crop returns and in checking agricultural development. The 

 land areas included in the malaria regions are the most fertile lands 

 in the United States. The medical side of the problem is well under- 

 stood and cared for by the proper treatment. The Government is 

 spending enormous sums of monej^ for protection in small towns and 

 in certain cities through the Public Health Service. The agricul- 

 tural side is neglected and little understood. The rural side of the 

 problem overshadows all other interests in importance. It is the side 

 upon which definite constructive information is lacking. The investi- 

 gation is worthy of ample support, the work is within the function 

 of the Bureau of Entomology, and it is advised that in order to hold 

 the present work together and continue the same efficiently further 

 provision must be made for men and for facilities. 



House-fly control. — A test was begun about two years ago of the 

 durability of various types and grades of screen-wire cloth as used 



