62 ANNUAL REPORTS 01 DEPARTMENT OF AGRICULTURE, 1 
Radio Isotopei Used To Study House Fly Dispersal and 
[nsecticidal Resistance 
Further studies were made to obtain more information on the rate 
and distance of dispersion of flies marked with radio isotopes. House 
flies mikI black blow flies were marked with radioactive phosphoric 
acid. These investigations demonstrated thai flies disperse rapidly 
and cover long distances within a few days. Black blow Hies were 
recovered 16 miles from the release point within 18 hours. The max- 
imum distance of recovery of this species was 28 miles. House flies 
did not migrate as far but were found to fly long distances. ( hie was 
taken 20 miles from the point of release. This apparently is the 
longest flight recorded for this insect. The information on the rate 
and extent of spread of flies has an important bearing on spread 
of diseases, spread of resistant insects, and source of flies in different 
areas. 
Radioactive DDT was utilized in effort- to develop information on 
the mechanism of insecticide resistance in flies. Other studies showed 
that flies killed by exposure to DDT residual deposits had absorbed 
less DDT than those killed by applying the DDT to the thorax. 
Studies on relationship of temperature to the amount of DDT ab- 
sorbed by flies showed that more DDT was absorbed at temperatures 
of 90 c F. than at lower temperatures. The mortality of flies, how- 
ever, was found to he greater at lower than at higher temperatures, 
indicating that temperature ha- even greater effect on the efficacy 
of DDT than previously believed. 
Agricultural Products Tested as Fly Attraetauts 
In efforts to develop attract ant- for housefly conl rol, a large number 
of agricultural products were evaluated. Fermenting products such 
a- molasses, brown sugar, malt, and certain fruits will attract flies 
!nt t heir degree of att ract iveness is ext remely variable. A number of 
synthetic organic compounds -how attractiveness in the laboratory 
but none of these have been explored sufficiently t<» determine their 
practical value. The use of liver baits in traps set around slaughter 
houses decreased the blow llv population about 85 to 95 percent in one 
test. 
Rotenone Still "Most Effective Control for Cattle Grubs 
Several hundred insecticides were evaluated for tin 4 com rol of cattle 
grubs. None of these were equal to rotenone insecticides. Recom- 
mendations for controlling cattle grubs with sprays have called for 
equipment delivering at least WO pound- pressure. Studies during 
the past year have shown that equipment delivering 200 pounds pres- 
sure will provide satisfactory control of third instar larvae. These 
BtudieS were cond UCt e< I in Oregon in cooperation with Oregon State 
( 'ollege ami in Texas and ( Georgia. 
Efficacious ( Control for Mites ami Lice Effecting Poultry Found 
Further investigations during the past year have demonstrated the 
eilica<\ of lindane insecticides tor controlling mites affecting poultry. 
Concentrations of i>..'» percent lindane applied thoroughly to all wall 
