JOURNAL OF ECONOMIC ENTOMOLOGY 
486 
[Vol. 17 
screen. The peak of the brood was reached September 21 (Fig. 13), and 
the fly-free-date was announced October 3. 
Warren county station, Spring Hill, 1922:—A total of 9,166 eggs were 
laid on the 100 wheat plants during a 29-day emergence period from 
September 8 to October 6, an average of 316 per day. From the two 
concentration cages 1,804 flies issued, and 524 were caught on the migra¬ 
tion screen. The crest of the brood occurred September 23, but a 
second heavy egg deposition took place October 1. The fly-free-date 
was announced September 30, seven days before the fall emergence was 
over. In this county there were only 12 wheat fields drilled before the 
fly-free-date in 1922. Some of these were so badly infested that they 
were ploughed up in the spring of 1923. As a result of such excellent 
cooperation the Hessian fly was reduced in numbers far below the danger 
point for the whole county. In 1923 the station was located at Indianola. 
Only 193 flies emerged from the concentration cages during a 26-day 
period from September 8 to October 3, and 92 were caught on the mi¬ 
gration screen, while only 16 eggs were laid on the 100 plants. The 
peak of the brood was reached September 25, and the actual fly-free- 
date was announced September 29. According to the county agent and 
crop reporters, the Hessian fly cost Warren County in 1922, between 
$125,000 and $150,000. In 1923 no injury was observed in the fields 
drilled on or after the actual fly-free-date, but a tax of about $750 is 
charged against the fly in the 12 fields drilled too early. The farmers in 
this county and several others were so convinced of the accuracy of the 
flaxseed count in predicting the actual fly-free-date that no wheat was 
drilled until the safe date was announced in 1923. 
REARING FLIES FOR EXPERIMENTAL PURPOSES WITH BIO¬ 
LOGICAL NOTES 
By R. W. Glaser, Sc.D., Department of Animal Pathology of the Rockefeller Institute 
for Medical Research , Princeton, N. J. 
Abstract 
The house fly ( Musca domestica ), the biting stable fly ( Stomoxys calcitrans) , and 
the cattle horn fly ( Lyperosia irritans) were used extensively in studies on the trans¬ 
mission of microorganisms by these insects. During the course of these studies simple, 
inexpensive and effective methods have been evolved for the rearing and handling of 
large numbers of flies. Special emphasis is placed on a type of breeding jar, on adult 
fly foods, on temperature, and on humidity. It was found that the last three have 
an important bearing on longevity and reproduction. To keep adult house flies 
alive long enough to obtain the full development of their ovaries and testes it is 
I 
