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REPORT OF THE ENTOMOLOGIST, 125 
and Mr. L. H. Titus, of San Gabriel, became impatient at the delay and requested 
Professor Hilgard, of the State University, to send them a chemist, and they would 
pay his expenses. In the month of April, 1887, Mr. F. W. Morse was delegated for 
this purpose, and he, too, finally discovered that hydrocyanic acid gas would kill the 
scales; but Professor Coquillett had made the same discovery over six months pre- 
viously, so that the credit of this discovery belongs to this latter gentleman. Much 
credit is also due to Mr. J. W. Wolfskill for the great amount of time and money 
that he has devoted to this cause. 
““ALEXANDER CRAW.” 
I am not aware that either of the other experimentors mentioned above have ever 
published the results of their experiments, nor have I been able to obtain any notes 
from them upon the subject. 
Many years ago Dr. George Dimmock, one of the editors of Psyche, made a num- 
ber of interesting experiments with pure gases on various insects, and his account 
of these experiments is given in the March-April number of that journal for 1877. 
The results obtained by him are briefly as follows: 
** Carbonic acid gas (carbon dioxide) did not prove fatal to beetles confined in it 
for one or two moments, but several sow-bugs (Oniscus) confined in it from twenty 
to thirty minutes never recovered. Mixed with oxygen in the proportion of three 
parts of the former to one of the latter, it did not prove fatal toa beetle confined in 
it three minutes. When mixed in the proportion of sixty-six parts of the carbonic 
acid gas to thirty-four parts of oxygen, it did not prove fatal to a beetle confined in 
it five minutes, nor to a wire-worm (Hlateridce) confined in it thirty minutes, and of 
several sow-bugs (Oniscus) confined in it fifty minutes, to some it proved fatal while 
to others it did not. 
** Carbonic oxide gas (carbon monoxide) did not prove fatal to beetles confined in 
it ten minutes, nor to butterflies confined in it thirty minutes. : 
** Hydrogen did not prove fatal to a beetle and butterfiy confined in it five minutes. 
‘* Oxygen did not prove fatal to a spider confined in it one hour, nor to a beetle 
confined in it for three days. . 
‘* Nitric oxide (NO) proved fatal to a beetle confined in it only fifteen seconds, 
while several sow-bugs (Oniseus) confined in it from forty to sixty seconds never 
recovered.” 
My own experiments with the nitric oxide mixed with air did not prove as suc- 
cessful as those made by Dr. Dimmock with the pure gas; in fact, the brown, fuming 
tetroxide proved more fatai to the Icerya than did the colorless oxids. 
I first began experimenting with gases in the month of September, 1886, and have 
since continued it at intervals up to the present time; an account of these experi- 
ments will be found at the end of this report. Among the numerous gases tried 
none have given as good satisfaction as the hydrocyanic acid gas; an account of the 
discovery of the effects of this gas is given in the paper by Mr. Craw, reproduced 
above, and need not be repeated here. Several of the other gases experimented 
with by me have not as yet been given sufficient trial to justify me in reporting 
either for or against their use as insecticides. 
In the month of Apvril, 1887, several of the fruit-growers of San Gabriel, who had 
become acquainted with the results that Mr. Wolfskill, Mr. Craw, and myself had 
obtained with the hydrocyanic acid gas, applied to Prof. E. W. Hilgard, of the Cal- 
ifornia State University, at Berkeley, for a chemist to assist them in experimenting 
with various gases, and he delegated Mr. F. W. Morse. Mr. Morse experimented 
with about half a dozen different kinds of gases, but found none so effectual as the 
hydrocyanic acid gas, which I had used over six months previously. His report 
will be found in Bulletin No. 15, Division of Entomology, of this Department. He 
was the first to use an apparatus for agitating the air in¢he tent, but this idea ap- 
pears to have originated with Professor Hilgard, who writes me that he instructe 
Mr. Morse to always agitate the air in the tent after introducing the gas. i 
In the months of September and October, 1886, Mr. Albert Koebele, one of the 
entomological agents of this Department, made a few experiments with the liquid 
bisulphide of carbon, an account of which he gave in his report to Prof. C. V. 
Riley, published in the report of this Department for the year 1886, page 569. The 
results of these experiments, however, especially those made under a tent, are so 
discrepant as to leave one in doubt as to the value of the bisulphide as an insecticide. 
During the past season I have made several experiments with the liquid bisul- 
phide, the main object being to devise some method whereby it could be evaporated 
more quickly than by merely exposing it to the air, but the results of these experi- 
ments were not entirely satisfactory. I next manufactured the bisulphide by pass- 
ing the vapors of sulphur over red-hot charcoal and conducting the gaseous bisul- 
phide into the tent ; bubthe numerous experiments I have made with the bisulphide 
