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mens were recorded to survive the strength of 1 to 235 for one hour 
and three for 1 to 235 for two hours, but in these instances the speci- 
mens were all destroyed at the end of twenty-four hours, it not at the 
time being known that any might subsequently recover. In every 
ease all of the bugs were stupefied by the gas, and none were noticed 
to again become active until at least two hours had elapsed. With the 
1 to 150 strength for an hour, none showed signs of life at the end or 
five hours, but twenty hours later one could crawl and another feebly 
move its legs, and on the following day a third responded when probed 
lightly; at the end of a week the one seemed fully recovered while 
the others were still too weak to move about. It is evident from 
these tests that 1 to 155 gas for an hour is too weak for room fumiga- 
tion since not all fully exposed bugs may be destroyed. It is only 
fair to mention, however, that in’ practice we have known 1 to 150 
gas give seemingly perfect results in a number of instances. <At 
other times while greatly decreasing the pest its use has not been 
satisfactory. 
The eggs of bedbugs seem to be devitalized with the use of about 
the same strength of gas as is fatal to the active stages, but we have 
had little opportunity to make observations on this phase of the prob- 
lem and therefore speak with reserve. Seven eggs laid within thirty 
hours of their exposure failed to hatch after treatment for two hours 
in 1 to 125 gas, the space in this case being a fairly tight room in a’ 
plague house and the eggs being fully exposed; nineteen eggs six days 
old failed to hatch after exposure for one hour in 1 to 150 gas in the 
dark room referred to above. Check eggs were not preserved. No 
eggs hatched in numbers of seemingly sound ones taken from treated 
railway coaches at the beginning of that work. It may seem strange 
that eggs should be devitalized by the gas, but in experiments con- 
ducted here three years ago it was determined that scale insect eggs 
(Diaspis pentagona and other species) suecumbed to 1 to 300 gas; in 
fact, it was observed that eggs of a species of Dactylopius lost their 
vitality from an hour’s exposure in the strength of gas mentioned 
when adults escaped death. Check lots of eggs of the different kinds 
exposed hatched. 
The common roach (Hctobia germanica) succumbs to overnight 
treatment with 1 to 100 gas. The kitchen and seullery of one of the 
Cape Town clubs swarmed to an almost ineredible extent with this 
insect. The spaces were treated with the strength intimated, and in 
the morning not less than a half bushel of dead roaches were swept 
up. About fifty that bore ootheca were boxed and brought to the office 
and no eggs hatched from them; there was no check test, however, 
to determine if such eggs would hatch were the females otherwise 
destroyed. 
The fleas on a dog confined in a room, treated for an hour with 1 to 
180 gas, were all destroyed; one hundred were removed and kept 
