9 
once introduced it can be readily understood how the insect spread 
over the apple-growing area by the shipping.of fruit from one section 
to another. The spread is found to be along the lines of transporta- 
tion. It was retarded in a great measure by the fact that many 
orchards were isolated. A well-marked case of immunity resulting 
from isolation is shown in the case of Mr. Perrine’s orchard at Blue 
Lakes. This orchard was free from the insect until two or three years 
ago, and is now but little infested. Mr. Perrine thinks the moth was 
introduced into his orchard in old boxes. The spread from orchard to 
orchard by the flight of the moths has been comparatively slow, and 
usually follows a river valley. 
LIFE ZONES AND PRESENT DISTRIBUTION. 
The status of the insect has been studied as far as the data at hand 
would permit. The life zones found in Idaho (fig. 1.) may be de- 
scribed as follows: 
The Boreal zone comprises that part of the State known as the Panhandle, a strip 
along the northeastern side of the State and a large area in the central part of the 
State which is connected with the eastern strip. 
ZZ BOREAL.. 
= TRANSITION. 
MI] UPPER SONORAN. 
Fig. 1.—Map of the Pacific Northwest, showing life zones—locaities infested by codling moth indi- 
cated by dots. 
The Transition zone is limited to an irregular area in the north and a fringe around 
the Boreal in the south. The southwestern and southeastern parts of the State are 
also in this zone. The Transition area in the northern part of the State is somewhat 
different from that of the southern part, on account of the larger amount of rainfall. 
