BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 61 
Table 19. — Shipments of parasites to foreign countries during the fiscal year 
Country 
Host 
Parasites 
Egypt 
Mediterranean fruit fly 
Opius humilis Silv. 
Do 
do 
Diachasma tryoni Cam. 
Do 
do 
Do 
Pink bollworm 
Oriental fruit moth 
Italy 
Do 
do 
Fiji __ 
Mediterranean fruit fly. .-- 
Do „ 
do 
Do 
do. 
Tetrastichus giffardianus Silv. 
Poland 
White grubs 
Elis spp. 
Do 
do 
Tiphia spp. 
Mexico 
Pink bollworm 
Eieristcs roborator (Fab.) 
Do 
do 
Microbracon brevicornis Wesm. 
CONTROL INVESTIGATIONS 
TESTS OF HOUSEHOLD INSECTICIDES AGAINST HOUSE FLIES 
The testing of various household insecticides against house flies hy the 
method of Peet and Grady and by a turntable method, which was devised in 
the Division of Control Investigations, was carried on in cooperation with 
various insecticide manufacturers. The object of these studies is to improve 
the methods of testing so that satisfactory specifications for fly sprays can be 
written. One of the requirements is the adoption of a standard insecticide 
with which unknown samples may be compared. Phenothioxin was found to 
have some promise as a standard. 
SURVEY OF THE INSECTICIDAL VALUE OF DOMESTIC SPECIES OF 
ROTENONE-BEARING PLANTS 
In cooperation with the Division of Drug and Related Plants of the Bureau 
of Plant Industry, the insecticidal action of extracts of some 30O samples of 
roots of Cracca, chiefly C. virginiana, collected in 18 different States, was tested 
against house flies. The most effective roots were found in eastern Texas, south- 
western Georgia, and Florida. The plants found north of Georgia possessed 
very little toxicity. The sample most toxic to house flies was collected in 
Harrison County, Tex., and contained 1.8 percent of rotenone. The demonstra- 
tion of correlation between the Durham qualitative color test for rotenone and 
the effectiveness of the extracts of Cracca has facilitated the search for plants 
of high toxicity and the selection of plants for cultural experiments. 
INSECTICIDAL EFFECT OF ALCOHOLIC EXTRACTS OF PYRETHRUM 
In cooperation with the Food and Drug Administration, tests of the insecti- 
cidal action of samples of extracts of pyrethrum were made to find which of 
the three methods of chemical analysis for pyrethrins was best correlated with 
the insecticidal properties. Tests were also made on the insecticidal effect of 
mixtures of alcoholic solutions of pyrethrins and rotenone. 
TESTS OF ORGANIC COMPOUNDS AGAINST MOSQUITO LARVAE 
S«'me 200 synthetic organic compounds, made or obtained by the Division of 
Insecticide Investigations, were tested during the fiscal year against mosquito 
larvae. In addition to phenothiazine, which was more toxic than rotenone to 
culicine mosquito larvae, 14 other compounds were found that compared favor- 
ably with rotenone in toxicity. Organic compounds of iodine were found to be 
more toxic than organic fluorine compounds. 
GELATINE-FILM METHOD FOR TESTING INSECTICIDES 
A method applicable to testing the effect of light on the toxicity of various 
types of insecticides by imbedding them in a thin film of gelatine was worked 
out during the past year. When cabbage worms were fed gelatine film con- 
taining derris, in cabbage-leaf sandwiches, they were killed. Pyrethrum powder 
fed in the same way did not kill them. On the other hand, the cabbage worms 
