14 
RELATION OF DISTRIBUTION TO LIFE ZONES. 
Althouoh the codling moth may be brought into a section o.f countiy, 
it may not be able to obtain a foothold on account of the adverse cli- 
mate. In other regions it i.s never ver}^ injurious, or it may be quite 
injurious one year and almost absent the next; but in warmer regions 
it reaches the maximum of destructiveness. 
In order to study these conditions the writer has used the life zones 
of Dr. C. Hart Merriam (PL I). Upon consulting this map one 
finds that there are seven different zones in the United States. In 
• the eastern portion they, in a general way, extend east and west, 
while in the western part they are broken into irregular areas by the 
mountain ranges. There are man}^ important subdivisions of these 
zones, depending principall}^ upon the amount of moisture and the 
milder and more temperate climate near the seacoasts. 
BOREAL ZONE. 
The principal apple-growing regions of this zone are in Nova Scotia, 
northern Maine, northern Michigan, and western Oi»egon. Except 
for the Pacific coast strip, only the. more hard}^ varieties of apples are 
grown in this zone. There is a great lack of definite data in regard 
to the exact amount of injur}- the insect cauges in this zone. As near 
as the writer can learn, the injury is never so great as it is in the next 
warmer zone. According to Cordley, the insect is present in small 
numbers in the Pacific coast strip and is doing but a comparative!}^ 
small amount of injury. 
TRANSITION ZONE. 
The transition zone includes the greatest apple-producing regions 
of the United States, the Alleghenian area comprising the zone in the 
eastern mountain States, including the larger part of the apple-grow- 
ing regions of New York, Pennsylvania, and Michigan. Although 
the injuiy, which varies with the seasons, is greater in the transition 
than in the boreal zone and less than in the austrafl, no record of 
definite ^percentages has been found during the present «tudy. 
In the arid area of the transition zone the loss is less than in the 
Alleghenian area. Various estimates of from 5 to 25 per cent of 
damage have been given. At Moscow, Idaho, which partakes more 
of the Pacific coast strip characteristics than of those of the arid area. 
Professor Aldrich records the amount of injury as 21 per cent for 
1899, 10 per cent for 1900, and 5 per cent for 1901. Professor Piper 
states that in 1898 the average damage about Pullman, Wash., was 10 
per cent, and some orchards were injured 25 per cent; in 1902, about 
5 per cent. Professor Gillette reports from 35 to 80 per cent at Fort 
Collins, Colo., varying with the degree of infestation in the localit3^ 
