3G ANNUAL EUBPOBTS OF DEPARTMENT OF AGRICULTURE, 1953 
Further experiments showed that when DDT is injected into highly 
resistant flics, they metabolize it more rapidly than do susceptible 
flies. DDE is again the main product of metabolism, but there is 
also a considerable quantity of some unidentified metabolic product. 
By careful dissection, the nerve ganglia of individual house flies 
were isolated and measured amounts of DDT applied. The ganglia of 
resistant flies required far more DDT to cause symptoms of poisoning 
and also recovered from poisoning much more rapidly than did the 
ganglia of susceptible individuals. 
Bureau entomologists have compared the life cycles of six suscepti- 
ble and two resistant strains of house flies and have found no signifi- 
cant diiFerence. The percentage of resistant eggs hatched was 
generally lower than the percentage of eggs of susceptible strains. No 
difference in the iodine number of the fat from susceptible and 
resistant flies was found. 
Attempts are being made to develop a colony of house flies resistant 
to allethrin. This colony is now in the eighth generation, each genera- 
tion being exposed to allethrin. Some resistance is apparent but it 
is at a very low level. 
Chlordane-Resistanl Roaches Tested 
In collaboration with the National Pest Control Asociation. a 
colony of German roaches was established in the Beltsville, Md., 
laboratory and tested for resistance, The ancestors of these roaches 
were collected at Corpus Christi, Tex., from buildings in which 
chlordane failed to control the pests. When compared with suscepti- 
ble strains, very high resistance to chlordane and definite resistance 
to DDT and lindane were proved. So far as known the resistant 
roaches had never been previously exposed to DDT. Nevertheless 
they absorbed this material and metabolized it to DDE at a greater 
rate than the normal strain. DDE was not the only metabolic product 
but was the only one identified. 
Physiological Data on Insects Tabulated 
Tables on chemical constituents of insect blood, the chemical analy- 
sis of insect tissue, free amino acids in insect blood, and the effects of 
temperature on insects, were prepared by Bureau personnel for inclu- 
sion in a I landbook of Biological I )ata to be published by the National 
Research Council. 
CEREAL AND FORAGE INSECTS 
Grasshopper Control and Research 
f psurge in range gra*$hopper$ predicted 
Surreys throughout 26 western States in the late summer and fall 
of L952 to determine the location, abundance, and specie- of grass- 
hoppers indicated an increase in ranee grasshoppers in many areas. 
The largest of the problem areas included 160,000 acre- of privately 
owned or controlled rangeland in the Texas Panhandle, 100,000 acres 
in contiguous Cimarron County, Okla., 425,000 acres in northeastern 
\cw Mexico, and ab<»ut L00,000 acre- m southeastern Colorado. 
