62 ANNUAL REPORTS <»f DBPABTMEN1 OP AGRI< ULTUBS, I 
poisoned by crawling over pyrethruni-impregnated tiim< and were not 
(I when they crawled over films Im I with derria, Pyrethm 
this case acted as a contact Insecticide while the derria powder did not 
Tin: BFFBC1 OF low TEMPERATURES ON LARVAE OF Tin: CIGARETTE B] 
As a preliminary step toward Investigating the possibility of elimlii 
the ciga tie In tobacco by holding it In commercial coW 
storag were made to determine the temperatures 
kill d cigarette beetle. The results showed that fr< 
tratures were ssary Cor the destruction of the larvae if the \ 
e w< re of sufficient Length. 
RELATIVE TOXICITY OF ARSENATES OP CALCIC M 
Experimental work has shown thai there may be a wide variati 
toxicity of calcium arsenates containing the same amounts of 
and arsenic pentoxide. Tests with silkworm larvae have shown thai calcium 
taining water of crystallization were much more ; 
analogous anhydrous compounds. Certain anhydrous compounds £ail< 
at the highesl dosages taken by the larvae, while the analog n< bj I 
compounds were very toxic. 
ATMOSPHERIC FUMIGATION OF BALED COTTON 
The r\\h rimental w< rk In fumigation of baled cotton at atmosphei I 
impleted within the fiscal ;• 
STERILIZATION OF GRAPES FROM SPAIN 
Grapes imported from Spain were treated in commercial quantities 
jes in New York and Boston for possible infestation with the Mediter- 
.1 fruit fly. The method of applying the treatment and the super* 
of iis application during the first part of the season w< 
the Division oi Control investigations. 
STERILIZING RICE STRAW BY HEAT 
A method of sterilizing imported rice straw was worked out which con 
In placing the hah- of straw in a vacuum chamber, reducing tin- pressure, and 
then applying steam at 10 pounds above atmospheric pro-arc and holding it 
{"•a- 2 'Phi- treatment can he applied t" bales of rice straw whl 
: 30 i i unds pt r cubic t'<"'i In density. 
FUMIGATION OF VETCH SKID 
Tests were i lade to d< tern Ine < l » the concentrate n of two fun Ig i 
cyanic acid and carbon disulphide, that could be applied to I without 
:• of Injury, and i "J i the concentration aecessarj to kill the \ 
stages of the weevil Bruchus brachUUit Pahr. which might ained 
t herein. 
MISCELLANEOUS CONSTRUCTION AND TESTING 
Considerable work was done In testing car-fumigation 
Mexican border n> determine whether the Improvements made within the 
year would make it possible to reduce either the dosage of hydrocyanic 
ition or the period of exposure. 
INSECTICIDE INVESTIGATIONS 
During the fiscal year chemists working under the direction of the [i 
on were assigned to the following field laboratories: Manhattan, K 
sist in the fumigation work carried on by the Division of Cereal I 
i e insect Investigations; Vincennea, lnd., t<» assist in the Btn dling 
moth control conducted there by the DfVision of Fruit insect Investigations; 
and Takoma Park. M « 1 to assist with closely related work of entomol 
of th • i ». islofi ©f Control Investigations. Xh« UisectUlde laborat<»rj 
\v was transferred in lVhni:u\\ l «.»:;.. to Yakima. Wash., in 
