BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 65 
the resistant fly shows typical tremors as does the susceptible insect. 
In the resistant insect the tremors last only a relatively short time, 
showing that metabolism or some other mechanism has eliminated 
the symptoms. 
New Compounds Tried Against House Flies 
An experimental insecticide from industry, now called Pyrolan, 
was found to be about equal to pyrethrins in knock-down and kill. 
Two other products of industry, isodrin, a stereoisomer of aldrin, 
and endrin, a stereoismer of dieldrin, were found to be highly toxic 
to house flies. Two chlorinated turpentine materials were found to be 
about one-fifth as toxic at toxaphene. 
Studies on scabrin, the insecticidally active ingredient obtained 
from Heliopsis scabra, have been continued. Studies on the effect of 
five antioxidants on scabrin in oil sprays have been inaugurated. In- 
dications to date are that all these materials are rather effective in the 
stabilization of this toxicant. Numerous extracts of various parts of 
Heliopsis and Helianthus species have been tested in order to deter- 
mine which fractions contain insecticidally active principals. Syner- 
gism was demonstrated for scabrin mixtures with the following 
pyrethrum synergists: Sulfoxide, piperonyl butoxide, piperonyl 
cyclonene, w-propvl isome, a benzyl propyl ether, and MGK Synergist 
264. 
TOXICITY OF INSECTICIDES 
Dairv Cows Absorb Very Little Insecticide From Treated 
Alfalfa Hay 
Alfalfa hay containing chlordane and toxaphene residues has been 
fed to dairy cows over a 2-year period. Milk samples were taken 
every 10 days and analyzed. Results of the analyses did not indicate 
the excretion in the milk of measurable amounts of these materials. 
When larger quantities of the insecticides were given in oil solution in 
capsules or mixed with the feed, analyses indicated that measurable 
amounts were excreted. 
Dairy cows were also fed on alfalfa hay which had been treated 
with lindane, and samples of milk were analyzed every 10 clays. The 
residue on the hay was very low, so larger amounts were given in oil 
solution in capsules and mixed with the feed. Benzene hexachloride 
was detected in the milk samples. 
Alfalfa hay containing methoxychlor residues has been fed to dairy 
cows for long periods. No methoxychlor has been detected in the milk. 
When considerably larger dosages of methoxychlor were fed in the 
form of oil solutions in capsules, the insecticide was detected in the 
milk. 
CHEMISTRY OF INSECTICIDES 
Allethrin-Related Compounds Synthesized and Tested 
A number of compounds related to allethrin were synthesized and 
submitted for entomological tests. Among these was the compound 
having a furfuryl group in place of the allyl group in allethrin. This 
