96 
and the cyanide was weighed out and placed by the jars. Every- 
thing being in readiness, the attendants put in the cyanide by begin- 
ning on the upper floors and passing rapidly to the lower floors. 
The doors were then closed, locked, and kept so for two days. Brick 
walls being porous, and the windows not as tight as desired, much of 
the gas escaped. Persons walking within 100 feet of the building, 
on all sides except that from which the wind was blowing, could 
detect the odor of the gas the entire time. This made it desirable to 
leave the building closed for a period longer than usual. When the 
building was opened two days later most of the gas had escaped. 
The insects were very abundant and in all stages of growth, and 
in many cases the eggs almost coated the slats on the beds. Many of 
the eggs had hatched several weeks earlier, however, and it was nec- 
essary to pick them over carefully to find good ones for observation. 
This was done, and 10 apparently sound eggs were taken to the 
laboratory and placed in “* stender ” dishes for examination before the 
charges were placed. The day after the building was opened 101 
eggs that had not hatched were collected, and these also were placed 
in “stender ” dishes for examination. All of the eggs in the first 
lot (1. e., those taken before fumigating the building) hatched within 
ten days. ‘The eggs collected after the building was fumigated were 
examined every few days for two weeks, but not a singie one hatched, 
and they shriveled up and lost their plump appearance after a few 
weeks. 
An examination of the insects the day after the building was 
opened proved that all were dead and no eggs appeared to hatch 
afterward, although examinations were made frequently for a period 
of several weeks. Though this work was done in June, scarcely an 
insect could be found in the building as late as December 22. This 
appears to be conclusive evidence that fumigation with hydrocyanic- 
acid gas will destroy some classes of insect eggs. It is likely to be 
most effective on those with a large micropyle, like that of the eggs 
in question, and might not be effective on those with heavy shells 
suited to stand weather conditions in the field. We are now arrang- 
ing to study its effect on the eggs of the scurfy scale (Chionaspis 
jurfura Fitch). , 
Rooms used for storing food products have been treated by fumi- 
gating with hydrocyanic-acid gas under our directions also. These 
rooms had become seriously infested with the croton bug (Blattella 
germanica Linn.). Before fumigating these rooms all food prod- 
ucts that had been opened, such as butter, lard, etc., in fact, all 
materials with a moist exterior, were removed from the building. 
Such materials as boxed oatmeal, coffee, flour, sugar, canned goods, 
sealed packages of preserves, etc,, were left inside, 
