BUIiEAU OF ENTOMOLOGY AND PLANT QUABANTINB 63 
the interest of better cooperation with the Yakima laboratory of the Division 
of Fruit Insect Investigations. 
Search among plant materials for new insecticidal compounds was continued. 
Perhaps the outstanding result was The finding of anabasine in the haves 
and roots of the tree tobacco {Nicotiana glauca) of the Southwestern States. 
Anabasine is an alkaloid, very similar to nicotine in its physical, chemical, and 
insecticidal properties, which was first prepared synthetically in the Division 
of Insecticide Investigations several years ago, and which was later found 
in a Russian weed, namely, Anabasis aphyUa. 
Many plant samples reputed to possess insecticidal properties were received 
from various tropical countries, and 12 of them, namely. " Casearia timuo", 
Cassia chamaecrista, Croton capitatus, Helenium autumnale, II. tenuifolium, 
Ichthijometliia sp. (bark), Jacquinia keyensis, Lonchocorpus capassa, L. mono- 
spennus, Alachua pomifera, Piscidia communis, ami Pteroearpus angolensis, 
were put through an exhaustive chemical examination, without, however, the 
finding of any particularly promising compounds. Derris and cube continue to 
hold front rank as organic insecticidal materials, and the study of them was con- 
tinued. Considerable progress was made in the attempt to correlate the toxicity 
of particular samples with various chemical determinations, which it is hoped 
will lead to the possibility of evaluating such materials in the chemical laboratory 
without recourse to laborious biological testing. A critical study of the methods 
of determining rotenone was also carried out. which unearthed certain errors in 
the previously used procedure and led to the development of a more satisfactory 
method. Cracca virginiana, or devil's shoestring, continued to be the only Ameri- 
can plant in which rotenone has been found. During the year an exhaustive 
study was made of several hundred samples. Of these samples, 330 were col- 
lected by the Bureau of Plant Industry in its survey of the occurrence of this 
plant over the United States, and the results show that the best samples come 
from Georgia, Florida, and Texas. Two samples were found that contained 1.8 
percent of rotenone: many contained only traces or none at all. 
Considerable attention was devoted to nicotine, including a search for insoluble 
nicotine compounds. One promising new material of this class was developed. 
This product, called nicotine-peat, is the result of the combination of nicotine 
with powdered peat. Some peats when used in their natural state hold as much 
as 9.9 percent of nicotine in relatively insoluble form, and after simple acid 
treatment some others can hold as much as 13.7 percent. A second material, a 
solid soluble by-product of the other, known as nicotine humate, was developed at 
the same time, and may find a place as a substitute for the more volatile 
nicotine sulphate. It contains about 33 percent of nicotine. 
The study of pyrethrum as an insecticide was renewed, and some important 
forward steps were made. A method was developed for preparing one of the two 
active principles, namely, pyrethrin II, in a high state of purity by a method 
much more simple and much less drastic than any previously used. Considerable 
progress was also made toward a similar separation of pyrethrin I. As a result 
of these studies it will be possible to test the toxicity of the two compounds sepa- 
rately and determine their relative insecticidal value. A new and much si] 
method of determining pyrethrin II was developed which will facilitate not only 
research studies on pyrethrum but control work in analytical laboratori 
well. 
Of the synthetic organic chemicals made in the laboratory, only two c im- 
pounds, namely, phenothiazine and phenothioxin, seem to merit particular at- 
tention. Phenothiazine. an organic sulphur compound, with the formula 
CisHsNS, was given a field trial against the codling moth in the summ< 
1034. The crude material then available commercially was only abo 
percent pure and very dark colored, and the rather poor results obtained are 
perhaps to be attributed to These facts. A new method of preparing the product 
was developed by which it is easy to prepare a pure, light-colored product. At 
the suggestion and under the guidance of the Division of Insecticide Investiga- 
tions a large commercial concern undertook production of phenothiazini 
the new method, and large hutches of excellent material became available to 
the bureau for testing in the spring of 1935. Many substituted derivative 
phenothiazine wore prepared, but all proved les> toxic and hence of little in- 
terest. Effort was also made to develop pyridine derivatives, similar to the 
phenothiazine derivatives, but nothing promising was obtained. The other 
compound that in preliminary te>ts showed marked toxicity to c<Hlliim moth 
was phenothioxin. Methyls of preparing both a crude, oilv material eOtttail 
