2 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE, l 9 19 
In view- of the toxicity of residues From certain of the new insect icides, 
special toxicological studies are being conducted in cooperation with 
other Bureaus in the Department of Agriculture, the Food and Drug 
Administration of the Federal Security Agency, and several State 
agricultural experiment stations. 
Measures to keep the oriental fruit fly from reaching continental 
United States were strengthened through stricter quarantine regula- 
tions, including disinfestation of aircra ft. and further study <>f means 
ni controlling the pest in Hawaii. Walter Carter, of the Pineapple 
1; ! stitute of Honolulu, was appointed to organize and d 
an expanded research program to combat this fly. 
A new Division of Golden Nematode Control was established to co- 
operate with State and locaj in efforts to control and prevent 
further spread of this imj ortanl pest of potat i -. Harry L. Smith. 
leader of the golden nematode project for the past year, heads this 
nevi Division, with headquarters at Hicksville, N. Y. 
Ralph A. Sheals, formerly in charge of the Bureau's Division of 
Gypsy Moth Control, was appointed assistant to W. L. Popham, a 
ant cnief of the Bureau in charge of control operatic 
INSECTS AFFECTING MAN 
The research on insects affecting man is supported largely by funds 
transferred from the National Military Establishment, although cer- 
tain aspects of the wort are closely coordinated with related aet ivitios 
under regular Bureau appropriation-. The investigations for the 
armed services are being conducted in cooperation with the oflici 
the Surgeon General, the Quartermaster General, and tin 1 Chief of 
Engineers in the Department of the Army, and of the Surgeon General 
in the Department of the Navy, and with the Department of the Air 
Force. 
House Flies Develop Resistance to DDT 
House flies in some area- have developed a marked resistance to 
DDT. During the summer of r.»i^ report- of the failure of this 
ticide to provide the usual high degree of fly control were rec* 
from many parts of the United Siate-. Investigations showed that 
improper application of DDT and failure to prevent excessive fly 
breeding were important factor- responsible for these failure-. How- 
ever, tests with flies collected from certain area- in Florida, I 
Texas, and California showed some of them to he 20 to 50 time- as 
tan! a- non resistant Laboratory strains. 
Thai !i< flies can develop resistance t«> the point of practical 
Immunity ha- been demonstrated in laboratory experiments. Si,. 
sive generations of flies 'hat survived exposure t«» DDT weir reared 
until a -train was developed thai wa- about 250 time- a- resistant H*> 
nonresistant strains. This selection required 3 years and ,; " genera- 
tions, in each of which about 90 percent of the die- were killed by 
increasing do* age* or exposui es. 
In \ iew of i he marked resistance of some fly strains to DDT, several 
p.. ble substitute Insecticides were investigated. Afethoxychlor, 
