342 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
about 4: 00 a. m. and probably was blowing 40 miles at 6: 00 a. m., 
and a strong wind was blowing at 2: 00 p. m. and a moderate breeze 
at 8:00 p. m. The maximum temperature of the 13th was 91, the 
minimum 70; 14th, 80 maximum, 72 minimum; 15th, 80 maximum 
and 67 minimum. 
The decrease in the number of flies was quite appreciable after this 
storm; the abundance of flies before the storm was about the same as 
before the storm of 1916 except Haematobia irritans which was very 
numerous prior to the late storm and was not abundant before the 
storm of 1916. This fly was practically exterminated during the recent 
storm, adult C. macellaria decreased about 75 per cent, M. domestica 
decreased about 50 per cent and Stomoxys caicitrans about 25 per cent. 
Adults of all species under observation were decreased to some extent. 
After the storm of 1916 there was never any appreciable increase in the 
number of adult flies, although weather conditions were apparently very 
favorable for increase. After the recent storm the increase in all species 
was rapid. This increase became noticeable about 15 days after the 
storm, this being approximately the duration of the immature stages 
of the species concerned. It is quite probable that many of the imma¬ 
ture stages as well as the adult flies were killed during the storms. 
This is caused by the washing and drowning of the larvae, as was noted 
in the last storm and may possibly be augmented by sea spray. It 
has been determined in preliminary experiments that a solution of 
sodium chloride as weak as .25 per cent is detrimental to breeding of 
some species of Diptera in certain cases. This destruction of larvae 
and pupae, together with the almost complete destruction of adults 
during the first storm, left a very few flies to breed and this together 
with the variable barometric pressures and storms never allowed an 
increase that was noticeable during 1916. The larger percentage of 
adults and the more uniform barometric pressure allowed maximum 
breeding after the 1919 storm. 
A typical observation on the reaction of adult flies to barometric 
pressure was made on November 21, 1916. Several hundred Lucilia 
sericata and C. macellaria were in a cage at the laboratory and under 
observation. They became very active from 9: 00 a. m. to noon and 
during this time the temperature increased from 66 to 75, the humidity 
fell from 87 to 60 per cent, the wind was blowing a light breeze from the 
northeast, the barometer rose from 29.05 to 29.15, at 2:00 p. m. the 
temperature was 74, humidity 56, the wind a light breeze and a little 
more from toward the east, the barometer was 28.95 inches, the flies 
were all quiet and most of the Lucilia were in hiding. The day was 
clear except for a few medium cumulus clouds clearing toward evening. 
The barometer fell slightly until 6: 00 p. m., when it began to rise and 
the wind changed to the northwest blowing in a strong norther. 
