. Barriers to progress may be opposed to the spread of the 
irious species from place to place, or directed to preventing the 
ividual insect from gaining access to its food or place of ovipo- 
on. 
. The capture of insects may be accomplished either directly, 
hand, or indirectly, by lures and traps; and their destruction 
an captured may, of course, be effected in a great variety of 
ys, differing according to circumstances and convenience. 
. Topical applications may be either destructive or repellant, 
3 nded to kill the insect or to drive it away. The destructive 
ncies are either in the nature of internal or external poisons,— 
ing by contact or by their action after being taken into the 
nentary canal. The internal poisons can rarely be used except 
the orders provided with masticatory mouths, which therefore 
) and chew their food before swallowing it; and they are not 
ally available against such insects as take their food by suction 
ough a beak or proboscis. 
Index* the above system of classification of remedial and preven- 
3 measures, we may now arrange, for convenient reference, the 
des of resistance to the attacks of strawberry insects which have 
s far been devised. 
1. Modes of Culture. 
a. Grass lands should sometimes be cultivated for two or three 
ji*s in some hoed crop, to expel the root-eating insects which 
our not only the roots of grass, but also those of strawberries, 
s measure is especially recommended against the various white 
bs. 
b. In the vicinity of towns where gas is manufactured, the 
e used in purifying the gas becomes saturated with sulphur, and 
umulates as a waste product, known as gas lime. In a fresh 
te this is destructive to both vegetable and animal life, but on 
usure to the air it is eventually converted chiefly into the car- 
late and sulphate of lime, both valuable fertilizers for many soils. 
'hese facts suggest the following procedure to free the soil from 
.ious insects, preparatory to a change of ci*ops. First treat the 
face to a dressing of fresh gas lime late in summer or early in 
umn, and plow this under at once, and then apply a second 
ssing of the lime to the plowed surface. A's the rain washes 
3 into the soil, it will destroy the earth-inhabiting insects both 
that part of the soil turned over and for some distance beneath. 
3 details of this procedure are still subjects for experiment, and 
ther the amount to be used, nor the length of time it is neces- 
y to leave the fresh lime in the ground before planting, have as 
been definitely ascertained. The value of this application as a 
iilizer will also vary according to the character and history of 
soil. 
