THE CODLIN MOTH IX IDAHO IN 1900. 



811 



About Lewiston the damage is somewhat less than in the southern 

 part. Professor Aldrich tells me that in 1899 the damage about Moscow 

 was 21 per cent., while in 1900 it was only about 10 per cent. 



I have been informed that in small valleys in the mountains the- 

 codling moth does no damage. The apple is the fruit most infested* 

 The injury to pears never exceeds 0*05 to 10 per cent. 



Introduction and Spread. 



Previous to 1887 the codling moth was practically unknown in Idaho^ 

 It was probably present before that time, but did so little damage as not 

 to be noticed. 



The moth, without doubt, came into the northern part by way of the 

 Snake River valley. Its spread was rapid, although checked to some 

 extent by the long distance between orchards. 



The sections which are shipping apples are now all infested. The- 

 newer orchards are more or less free, but cannot remain so very long. 



Resistance of Varieties of Apples. 



Only scattered observations were made upon this point, and these do 

 not harmonise. Some of the varieties in order of damage sustained 

 are : — 



1. Pewaukee (always badly infested). 6. Wealthy (very variable). 



2. Spitzenberg. 7. Ben Davis (very variable). 



3. Bell-flower. 8. Rome Beauty very variable). 



4. King. • 9. "Winesap (but little infested). 



5. Gravenstein. 



This question is believed to be one of the most important to be worked 

 out, as in general the apples given as least infested are the best varieties 

 for Idaho. 



Life-history of the Codling Moth. 



The life-history, as usually given, applies to the insect in a climate far- 

 different from that of Idaho. On this account I spent much time in 

 studying the variations in the life-history. 



The Egg. 



The eggs can be found at any time during the summer, either upon 

 the fruit or upon the upper surface of the leaves. In certain orchards the 

 eggs were almost entirely upon the fruits ; in orchards near by they were 

 nearly all upon the leaves. Where apples were in abundance there were 

 but few eggs upon the leaves, and where apples where scarce but few 

 eggs were upon them. Apparently the moth prefers to lay its eggs upon 

 the fruits. 



The eggs have been described as whitish, milk-like spots. They 

 adhere closely to the fruit or leaf, and even after hatching the shells 

 remain for a long time. When the egg is a few days old a brown horse- 

 shoe-shaped band appears, indicating the embryonic larva. 



The Larva. 



In from about six to eight days the larva is fully formed and breaks 



