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_ REPORT OF THE ENTOMOLOGIST. 49 
hibernation upon Plum in the egg state, the migration therefrom in 
ring to Hop, and the return migration in the fall have been fully 
proved in the States, and I have had the privilege of going over and 
verifying the same facts in the hop-fields of England, during the 
furlough which I took from the office last fall on account of con- 
tinued poor health. The experimentation in the way of remedial 
Measures against its attack have also been most successful and satis- 
factory. The results of the investigation are of such importance and 
interest that I have been unable to put them together and prepare 
the necessary illustrations for this annual report, and for these rea- 
sons they will appear in separate bulletin forminthespring. In the 
same way the results of the continued investigations of the Buffalo 
_ Gmats, concerning which a preliminary article was published in my 
last report, are held for future publication. ‘ 
The work of the Division in carrying out the provisions of the law 
for the establishment of silk-culture in the United States has en- 
tailed quite as much labor during the past fiscal year as in previous 
years, and the resulis obtained have been quite as satisfactory as 
could have been expected under the circumstances. The general 
scope of the work has included the distribution of Silk-worm eggs 
and books of instruction and the conducting of experiments with 
automatic silk-reels, as mentioned in previous reports. The sixth 
edition of the manual of instructions, “‘The Mulberry Silk-worm,” 
consisting of 3,000 copies, which was issued in May, 1886, has been 
practically exhausted and a more enlarged edition is now in the course 
of preparation. The public interest has centered in the filature, 
which has been visited by large numbers of persons who uniformally 
express delight at theexperiment. For a full statement of the work- 
ing of the filature and for other details in reference to the work in 
silk-culture I refer to the accompanying report of Mr. Walker. 
Experiments upon the Fluted or Cottony Cushion-scale of California 
and the other injurious scale-insects of that State have been contin- 
ued during the season, and results from the two agents detailed for 
this purpose are included in this report. To Mr. Coquillett, of Los 
Angeles, was assigned the duty of experimenting with gases. His re- 
port, giving the results of a long series of careful experiments, will 
prove of interest to the people of California. One of the principal dis- 
coveries made by Mr. Coquillett is the fact that hydrocyanic acid gas, 
when passed through sulphuric acid, is rendered harmless to the 
foliage of trees confined init. This will greatly lessen the cost and 
- labor of treating trees with this gas. The experiment with tobacco 
stems vaporized, an account of which will be found near the end of 
this report (experiment 128), is worthy of further investigation. 
Another gas that gives promise of being successfully used as an in- 
secticide is arseniureted hydrogen, which would have the advantage 
of cheapness as compared with hydrocyanic acid gas; but additional 
experiments are necessary before its claim can be fully established. 
t should always be borne in mind, both in the use of this gas and 
the hydrocyanic acid gas, that the ingredients are exceedingly poison- 
ous, and the greatest care should therefore be taken by the oper- 
ator. The history of similar cases of destructive insects introduced 
from other countries goes to show, however, that the introduction 
of the natural enemies that keep the Fluted Scale in check in its 
native country will prove more eilective than any other methods in 
subduing the pest and at the same time relieve the fruit-growers of 
the large expense attending the employment of even the mosi satis- 
AG 87——4 
