beetles never recovered. Incubation of eggs was recorded after 10 to 1) days. 
Mortality of larvae was recorded 3 to 5 days after the exposure period. 
Tests Conducted 
Three series of tests were made under tobacco warehouse conditions, 
The first series, conducted in July at Winston-Salem, Ne Ce, was exploratory. 
Five warehouses were included, 3 type A (semiclosed), and 2 type B (venti- 
lated). The DDVP was dispersed in three different ways--as a thermal- 
generated aerosol; as an emulsion spray on the exposed floor, walls, and 
underside of the roof; and as a solution sprinkled on the floor of the aisle 
only. 
In the second series, conducted in early October at Winston-Salem, the 
DDVP was dispersed as a thermal-generated aerosol. Three warehouses were 
included, all type A (semiclosed). 
In the third series, conducted in late October at Charleston, S. Ce, 
the DDVP was dispersed as a solution sprinkled on the floor of the aisle 
only. Three warehouses were included, all type C (closed). : 
Test insects were exposed in the free air space in all series, and some 
were inserted into the hogsheads of tobacco in the last two series, White 
rats were exposed in the first series; rats, monkeys, and humans were exposed 
in the third series. Air samples were taken in the third series and analyzed 
to determine the concentration of DDVP vapor in the air. 
Glass microscope slides were exposed at various locations in warehouses 
treated with aerosols to indicate distribution of the aerosol. 
EXPLORATORY TESTS 
Procedure 
In this series, thermal-generated aerosols were applied to 1 type A 
(semiclosed) and 1 type B (ventilated) warehouse. An emulsion spray was ap- 
plied to the exposed floor, walls, and underside of the roof in 1 type B 
warehouse, A solution of DDVP was sprinkled on the aisle only of 2 type A 
warehouses. The warehouse tenperatures ranged from 7° to 80° F. Relative 
humidity was about 70 percent. 
The aerosols were produced in a commercial thermal aerosol generator 
adjusted to produce 97 to 98 percent of the particles with diameters of 3 
microns or less, The generator was operated from a point outside the build- 
ing. The aerosol was introduced into each warehouse at one point (the second 
