10 
The Upper Sonoran comprises the area about the Snake River Valley. This area 
is continuous with the same zone in Oregon on the west and Utah on the south. An 
arm extends down the Snake River Valley on the western border. A small area of 
this zone is present in the valleys of the Snake and Clearwater rivers at Lewiston. 
At this point several of the Lower Sonoran fruits are grown. 
The relations of the codling moth to these zones are as follows: 
Boreal. — As no apples can be grown in this zone, this insect does not occur. 
Transition. — The insect occurs in this zone, but is never greatly injurious. At Mos- 
cow the injuries for the past three years have been 21, 10, and 5 percent, respectively. 
Many fruit growers have told the writer that the insect has its ups and downs, vary- 
ing from practically no injury to 25 per cent. Correspondents at Almo, Cassia 
County; Lakeview, Laclede, and Rathdrum, Kootenai County; and Paris, Bear Lake 
County, state that they can find no indications of the insect at those places. The 
observations of those in the best position to know indicate that these locations are 
not well fitted for the growing of apples. The northern part of this zone, however, 
is evidently more suitable for apples than the southern part. 
The Upper Sonoran. — From 80 to 90 per cent of the fruit raised in Idaho is grown in 
this zone. Some varieties of apples reach perfection. The codling moth reaches its 
maximum of numbers and destructiveness in this zone, and here the greater part of 
the investigation has been made. 
LIFE HISTORY OF THE CODLING MOTH. 
Many important variations in the life history of this insect were 
noted in 1901. 
THE EGG. 
As in 1900, many eggs were observed. In orchards where there 
were hut few apples eggs were found in enormous numbers. On one 
apple the number of eggs or remains of eggs was found to be 23 
(PL I. I))\ on another 17. It was difficult to ascertain the time of 
hatching of the eggs, hut the times of hatching of eight were found 
with reasonable accuracy. These hatched in from three to eight days, 
with an average of about live days. 
THE LARVA. 
In a day or so after the egg is laid, a horseshoe-shaped band, which 
is the embryonic larva, may be seen. Later the form of the larva 
may be easily distinguished. In about live days the fully formed 
larva breaks its way through the shell and immediately seeks to enter 
an apple. The writer has many times attempted to observe the hatch- 
ing of an egg and the entering of the apple, but has failed, although a 
few times the attempt was almost successful. The young larva of the 
first generation has been observed to spend some time upon the fruit 
and then to enter the calyx by squeezing its way in between the calyx 
lobes. 
In 1900 the earlier countings showed that about 60 per cent entered 
the calyx end. Without doubt this low percentage was caused by 
