BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 55 
Zineb alone is not an adequate remedy for the pickle worm and 
melonworm. Its insectieidal action, however, does contribute to the 
effectiveness of such insecticides as lindane, parathion, and DDT 
against them. 
These experiments were conducted in cooperation with the South 
Carolina Agricultural Experiment Station. 
Importation of European Insect Parasites 
Importations of foreign parasites for rearing and colonization in 
the United States continued at about the same rate as last year. 
Shipments of European corn borer parasites from France and Italy 
consisted of 40,500 field-collected corn borer larvae, of which 4,635 
were parasitized with Campoplex alkae E. and S., 2,183 with Micro- 
g aster tibialis Nees, and an undetermined number with Apanteles 
thompsoni Lyle. 
Fewer imported parasites of the European chafer were available 
this year for colonization in the infested area in New York. Ship- 
ments from the rearing laboratory in France included 124 puparia 
and 125 adults of Dexilla rustica (F.) and 111 adults of Micro- 
phthalmia euro pea Egger. 
Small consignments of Microctonus aethiops (Nees.) and Campo- 
gaster exigua (Meig.), parasites of the sweetclover weevil, were again 
forwarded from France to the North Dakota Agricultural Experiment 
Station. 
Four shipments, including six large boxes of European elm and 
fig scale material, were shipped from France to the California Agri- 
cultural Experiment Station. The material contained several spe- 
cies of parasites of the scales. 
CHEMISTRY OF INSECTICIDES 
Allethrin Adopted for Use in Aerosols 
Allethrin has been approved for use in household aerosols. One of 
the most effective of the synthesized pyrethrinlike esters, this insecti- 
cide is being produced commercially by two companies, using the 
method of synthesis developed by Bureau chemists. 
The Army has adopted allethrin as an alternate for pyrethrum 
extract in its aerosol bombs, thus making this country independent of 
imported supplies of pyrethrum, which was very difficult to obtain 
during World War II. The present selling price of allethrin is 
slightly lower than that of pyrethrum. 
Satisfactory analytical methods for the assay of technical allethrin 
and insecticides containing it have been difficult to devise. A method 
based on hydrogenolysis of allethrin to yield dihydrochrysanthemum 
monocarboxylic acid, which is then titrated, was developed in the 
Bureau's chemical laboratories. A cooperative study of this and sev- 
eral other proposed methods is under way in Government and industry 
laboratories. The current procurement by the Army of allethrin for 
aerosols makes the study particularly important. 
A number of pyrethrinlike esters differing from allethrin in vari- 
ous details of structure of the acid and cyclopentolone portions of the 
