14 



RELATION OF DISTRIBUTION TO LIFE ZONES. 



Although tlu! fodliiii>- moth iiiav 1)0 hrouo'lit into a scotioii 0"f country, 

 it may not l)r able to obtain a foothold on account of tlic adverse cli- 

 mate. In other reg-ions it is never very injurious, or it may be quite 

 injurious one year and almost absent the next; ])ut 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 (PI. I). Upon consulting- this map one 

 tinds that there are seven diU'erent zones in the United States. In 

 the eastern portion they, in a general wa}', extend east and west, 

 Avhile in the western part they are l)roken into ii-regular areas })y the 

 mountain ningcs. There are many important subdivisions of these 

 zones, depending principally 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, northerti Michigan, and western 0>eg-on. Except 

 for the Pacific coast strip, only the more hardy varieties of apples are 

 grown in this zone. There is a great lack of definite data in regard 

 to the exact amount of injury the insect causes 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 

 num])ers in the Pacific coast strip and is doing but a comparatively 

 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 Yoi-k, Pennsylvania, and Michigan. Although 

 the injury, which varies with the seasons, is greater in the transition 

 than in the boreal zone and less than in the austnul, 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 

 1891), 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 

 6 per cent. Professor Gillette reports from 35 to 80 per cent at Fort 

 Collins, Colo., varying with the degree of infestation in the localit}'. 



