48 
be an exterminative measure in the case of the gypsy moth, it certainly 
ranks as one of the very best control measures. Where infested wood- 
land was sprayed the past season in the manner indicated, notwith- 
standing an abundance of very unfavorable weather, from 60 to 80 per 
cent of the larvee were destroyed, and under favorable climatic condi- 
tions a thorough spraying soon after the eggs hatch will probably 
destroy 90 per cent of the larvee. 
Against ordinary leaf-eating insects it would be unnecessary to use 
the great amount of poison required in the case of the gypsy moth or 
elm leaf-beetle. Mr. Harold L. Frost, of Boston, Mass., who has had 
considerable experience in spraying trees to prevent the ravages of the 
cankerworm, tussock moth, and tent caterpillar, has found that from 
3 to 4 pounds of arsenate of lead mixture to 150 gallons of water gives 
most excellent results in destroying these insects; and this is about 
the rate at which it would seem necessary to use the poison for effect- 
ive results in ordinary cases. A comparison of the results of a large 
number of experiments and field tests which we have made show that 
from 3 to 4 pounds of arsenate of lead mixture are necessary to equal 
the effect of 1 pound of Paris green. With Paris green retailing at 
from 20 to 25 cents per pound, the cost of arsenate of lead mixture 
necessary to accomplish equal results would be somewhat greater than 
the cost of Paris green. But the arsenate of lead has many advantages 
over all other arsenical insecticides, prominent among which are its 
low specific gravity (being scarcely heavier than water), which renders 
it easily suspended in the spraying tank; its characteristic color, by 
which its presence on the leaves can be readily detected, and its great 
permanency on the foliage. Of course the chief merit possessed by 
this poison is the fact that when properly prepared it will not injure 
the foliage if applied at any ordinary strength. 
Another arsenate of lead—the di-plumbie arsenate—has been pre 
pared by Mr. Smith, at a somewhat less cost than the preceding, from 
nitrate of lead and arsenate of soda. Upon this insecticide our chem- 
ist.is now at work, and from field tests made this summer quite promis- 
ing results have been obtained. So far as is now known, there are no 
by-products available for use in the manufacture of arsenate of lead; 
hence the cost of this substance must be governed by the cost of the 
raw materials plus that of the processes involved in bringing them into 
available forms. From the economic as well as from the scientific 
standpoint the subject of the arsenates of lead offers a wide and inter- 
esting field for research—a field in which the chemist and physiologist 
must labor together. 
At the conclusion of this paper, Mr. Kirkland made a brief statement 
concerning the appearance of the European brown-tailed moth in east- 
ern Massachusetts, and exhibited specimens. The insect was appar- 
ently confined to four or five cities and towns. Most unfortunately, 
