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THE POTATO TUBER MOTH. 
31 
noticeable development for a few days at a time when the average 
mean temperature is low. 
Experiments were carried on in the storage rooms of an ice company 
at Pasadena to determine if low temperature acting for some time 
would kill the various stages of the moth or whether they could 
hibernate successfully. For these experiments the following stages 
were taken : Adults, pupa?, mature larva? in cocoons, and eggs. Two 
experiments were carried on at the same time. One lot was kept at 
32° F. for three weeks, while the other lot was kept for 35 days at a 
temperature of 38°-40° F. 
The results are summarized in Table 10: 
Table 10.- 
-Effect of 
ow temperatures on stages of the potato tuber moth. 
Time. 
Tempera- 
ture 
(constant). 
Adults. 
Pupae. 
Mature 
larvae. 
Eggs. 
21 days 
32° F 
40° F 
Most alive and active 
Alive 
...do 
Alive 
...do 
Alive. 
Over half were dead 
Do. 
In the cases where the various stages were alive they developed 
normally when taken from storage. In both experiments develop- 
ment was stopped in all stages while the material was in storage. 
These results show that the tuber moth may hibernate successfully 
where conditions demand it and that no development takes place 
below 40° F. Prof. Picard (83) says that no development takes place 
below 50° F. 
DISSEMINATION. 
The tuber moth is disseminated by two means, natural and arti- 
ficial. Of these two the former (by flight of the moth) is much the 
slower and, as it can hardly be controlled, is relatively unimportant. 
The most important spread of the tuber moth takes place through 
the movement of infested potato tubers. In this way the insect is 
assured of an abundance of food, and since the tubers are not allowed 
to freeze, the temperature is always favorable. In interstate and 
international shipments the moth is given every opportunity to 
spread and has probably been introduced at some time into every 
civilized country on the globe. 
It is even possible that a careful inspection will show that it is 
established in many localities where it is now unknown. This is 
especially likely to be the case in districts where the climate is cold 
and wet and therefore unfavorable for the insect's normal develop- 
ment. 
MORTALITY OF THE STAGES. 
The mortality in the various stages must be considered from the 
standpoint of whether the insect is working on potato tops or on 
stored potatoes. Under field conditions as a leaf miner the mortality 
