46 
their value is hence suggestive rather than final. Those which have 
to do with the San Jose scale, the harlequin cabbage-bug, and the 
cotton boll-weevil are perhaps of the greatest interest, and will be 
given first. 
The San Jose Scale. — In the fall of 1897, Professor Pettit, of 
Michigan, had five parallel burners fitted to an ordinary plumber's 
blast-lamp in such a way that a flame about ten inches wide could 
be directed against the surface of a tree, and several trials of this 
apparatus were made during the following winter on peach- and 
pear-trees badly infested with the San Jose scale. "The heat pro- 
duced by this lamp," he says, "is very intense, and great care must 
be observed not to allow the flame to remain at any one point long 
enough to injure the tree. The best results were obtained when the 
flame was steadily moved so that it covered a space of a yard in 
length in from five to ten seconds. The results seemed to show that 
the blast will kill the scale-insects with little or no injury to the 
tree. The trees were scorched in places where the flame had moved 
too slowly, and the care necessary to avoid the scorching appears to 
be the most serious drawback to the use of the blast lamp. In care- 
less hands much injury may be done in a very short time, while 
the skilful handling necessary for success would be rather expen- 
sive under ordinary circumstances. Good judgment must be exer- 
cised always, and the rapidity and effectiveness of the work will be 
much modified by the temperature of the air, the direction and force 
of the wind, the age of the trees, and the thickness of the incrusting 
scales." Referring to these statements in a recent letter, Professor 
Pettit writes that he intended that the lamp should be used only in 
connection with a spray, for burning off or loosening the outer lay- 
ers of a crust of scales so that a fluid insecticide might penetrate to 
those beneath. "I now realize," he says, "that the same effects may 
be obtained much more cheaply in other ways." 
By Professor Craig, of Cornell University, a torch much adver- 
tised for the destruction of insects was used May 19, 1903, against 
the San Jose scale on the apple, medlar, buffalo-berry, and dog-wood. 
Different branches were flamed in various ways to ascertain the time 
necessary to kill the scale and to determine the minimum exposure 
to the flame of the torch which would kill the cambium layer of the 
tree or shrub. In respect to time of exposure three methods of treat- 
ment were used : passing the flame so rapidly over the surface that 
it merely touched each point for an instant; moving it at the rate of 
one foot per second; and holding it stationary on the infested spot 
long enough to count one. The scales were reported to have been 
killed in every case save one, in which a twig of dogwood had been 
