142 THE PERIODICAL CICADA, 
1902. There were 240,000 peach trees in the field to be protected, 
and seven men were kept at work in this field for over two weeks, and 
by actual count it was found that these men killed more than 1,000 
cicadas each per day by hand collecting. Seventy thousand cicadas 
were collected in this field alone, and other men were employed in the 
smaller fields. so that Mr. Hoopes feels sure that at least 100,000 
were killed altozether. In spite of this work, however, a loss of 12,000 
trees was sustained out of the 240,000. 
DESTRUCTION WITH INSECTICIDES. 
The various treatments aiming at the destruction of the insects 
themselves lrave yielded satisfactory results, but to have any practi- 
cal value it is necessary to continue them daily or as long as the 
insects issue in any numbers. On a large scale, therefore, or over a 
considerable territory, in the presence of immense swarms, work of 
this sort will be ordinarily out of the question. The recommenda- 
tions apply particularly, therefore, to small areas or orchards. Such 
work may be directed against the Cicada the moment it emerges from 
the ground, while still in the pupal stage, but perhaps more readily 
and successfully against the insect after it has shed its pupal skin and 
is still soft and comparatively helpless, and with less ease, but still 
with some degree of effectiveness, after it has hardened and begun 
its aerial duties. 
Of the many substances experimented with few proved to be of 
much value, the best results being obtained with (1) pyrethrum or 
insect powder, using it both in the dry form and as an aqueous solu- 
tion; (2) kerosene emulsions; and (3) solutions of various acids. 
These substances either effected the immediate death of the insect, 
or attained this end indirectly by preventing its transformation from 
the pupal to the adult stage; in other words, rendering the last molt, 
impossible. 
Pyrethrum powder is a perfectly satisfactory destroyer of the newly 
transformed and soft cicadas, and has considerable efficacy against 
the mature and hardened individuals. The best results are obtained 
in the morning, before the insects have gained full strength to ascend 
and while the plants are still wet with dew. The powder may be 
puffed on the insects while clinging to shrubbery or on the lower 
branches of the larger trees. 
Pyrethrum powder is absolutely worthless against the pupz, which 
even when thoroughly coated with it, will often succeed in casting off 
their powdered skins and escape uninjured. The winged insects are, 
however, very sensitive to the powder, and after an Siplieoion soon 
show signs of uneasiness and in the course of a few hours fall helpless 
to the Saatchi. where, though they may continue to have the power of 
motion for a day or more, a fatal termination is almost sure to follow. 
