BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 95 
rupted by severe damage to the autogiro during the New England 
hurricane of September 1938. Reconditioning of the aircraft and com- 
pletion of tests in the spring of 1939 permitted actual field use of the 
equipment in June of the same year for treating an area near Green- 
field. Mass.. infested with the gypsy moth. Although the area treated 
presented unusual difficulties from the viewpoint of applying insecti- 
cides by means of a plane, the autogiro and the distributing apparatus 
operated successfully and without mechanical failure of any kind. 
The operations demonstrated that it was feasible to use rotary-winged 
aircraft over hilly, heavily wooded terrain, and that the method used in 
dispersing and distributing the insecticide was sound in principle. 
INSECTICIDE INVESTIGATIONS 
Efforts were continued to develop new and more effective insecti- 
cides. Many of the results were made available to the public by 
mean- of 58 scientific papers, comprising 1 technical bulletin, 10 
articles in the Bureau's E series, 1 in the ET series, and 46 articles 
in technical and trade journals. Ten patents were issued to members 
of the Division, and the monthly review of United States patents 
relating to pest control was issued regularly and distributed to a 
large number of foreign and American entomologists. 
CHEMICAL INVESTIGATIONS ON INSECTICIDAL PLANTS (TOBACCO, DERRIS, 
PYRETHRLM, ETC.) AND THEIR CONSTITUENTS 
Investigations of pyrethrum narrowed down to an intensive study 
of the one still unknown feature of the nature of the two insecticidal 
pyrethrins it contains, namely, the exact structure of the side chain of 
the alcohol pyrethrolone. The latter has long been suspected to 
contain an allene grouping. During the year two compounds con- 
taining allene groupings were successfully synthesized, and bromine 
was found to react with them similarly to the way in which it does 
with pyrethrone. Final and direct confirmation will be sought by 
isolating one of the products of the bromine reaction and preparing 
from it a substituted caproic acid whose structure is known. 
The work with rotenone-bearing plants was particularly character- 
ized by a renewed intensive study of derris and cube resins, with 
special attention to deguelin because all available information indi- 
cates it to be the next most important compound. Deguelin is be- 
lieved to exist in the resin in an optically active form, but no active 
crystalline material has ever been obtained, the deguelin heretofore 
available being the inactive form obtainable only after treatment of 
the resin with mild alkalies, which evidently racemizes it. The at- 
tempt to separate ordinary deguelin into its two optical components 
failed, but led to the discovery that it makes numerous complexes 
with various organic liquids, one of which, that formed with carbon 
tetrachloride, became the basis of a new method of estimating the 
quantity of deguelin present in a loot or resin. High-vacuum dis- 
tillation permitted the preparation of a solid substnnce containing 
over 8Q percent of optically active deguelin. but even this could not 
be made to crystallize ami yield the pure compound. The concen- 
trated material has shown insecticidal effects of the same general 
intensity as those produced by rotenone. 
