346 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
It is believed best that the central station of the sanitary depart¬ 
ment should keep on hand a supply of the para-dichlorobenzene and 
sell this to the people at, or nearly at cost. This measure will prevent 
high costs and will place the substance within easy reach of all. After 
the details of the application of the insecticide have been made known, 
then no excuse should be held valid for having calopus larvae in such 
containers, and if the town has yellow fever, then the offenders, no 
matter who they are, should be dealt with to the fullest extent of the law. 
The following is a brief synopsis of our experiments: (1) A prelim¬ 
inary test was made at the laboratory using camphor and para-dich¬ 
lorobenzene in powdered form, one gram to a liter of water. Twenty- 
five calopus larvae were placed in each jar. The camphor floated on 
the surface whereas the other substance remained on the bottom. The 
larvae showed greater distress, at first, in the camphor jar. Three 
hours later all larvae were found on the bottom of the jars. Those in 
the para-dichlorobenzene lot were in great distress, due, of course, to 
the greater concentration of the substance at this level. There were 
only five larvae alive in this jar, but they were unable to wriggle up to 
the surface. In the camphor jar there were eight larvae still alive. 
These tried at times to reach the surface, but were repelled when near 
it by the camphor in the water. Two hours later all larvae, in both 
jars, were dead. In the control lot, the larvae behaved as calopus 
larvae should, pupated in due time, and adults emerged. 
To determine whether the camphor or para-dichlorobenzene impart 
any odor to roses, or in any way affect their duration, three roses were 
placed in a jar containing a liter of water and two grams of camphor; 
three were placed in another vase containing instead two grams of 
para-dichlorobenzene. A check lot was also kept. After two days no 
change in color took place. The roses were then submitted to several 
people at the laboratory to note if any change in odor was noticeable. 
There was no change noted, in fact, the flowers looked exactly like the 
control lot. 
(2) A similar test was made with pupse; one gram of camphor, and 
one gram of para-dichlorobenzene to a liter of water was used. Three 
hours later all the pupse in the para-dichlorobenzene jar were dead and 
on the bottom. In the camphor jar all pupse were at the surface; 
three out of the ten were dead, but the living were in very great dis¬ 
tress. Upon shaking the jar to make them descend, they found great 
difficulty in again reaching the surface. One hour later all pupse were 
dead. 
(3) A large screen cage, 3 feet by 3 feet by 3 feet was used. 
In it were placed three moistening jars, 10 inches in diameter by 
3 inches high, each with a liter of water. To one of these was added 
