MONTANA EXPERIMENT STATION. 221 



graph we have shown that the stem mother's maxi- 

 mum power of production is upward of lOO young, and i^ 

 is probable that later generations can give birth to a similar number. 

 Acting on the basis that all of the young of each generation come 

 to maturity and produce the full unmber of young, we find that the 

 progeny of one stem mother during one summer is something enor- 

 mous. 



1st generation i aphis. 



2nd generation lOO aphids. 



3rd generation 10,000 aphids. 



4th generation 1,000,000 aphids. 



5th generation 100,000,000 aphids. 



6th generation 10,000,000,000 aphids. 



7th generation 1,000,000,000,000 aphids. 



Thus starting with one aphis in the spring we would have in the 

 seventh generation one trillion aphids, a number which the human 

 mind cannot appreciate. Under natural conditions, however, the in- 

 sects are decreased in number from one cause and another, all thro' 

 the season, so that, while they increase very rapidly, they never do 

 so to the extent above indicated. At the same time, however, it is 

 easily seen that the destruction of a large proportion of the first and 

 second generations will very markedly affect the numbers through- 

 out the season. There seems to be little doubt that the killing of 

 the first generation, by inclement weather in some seasons and the 

 absence of storms in other seasons account for tha great variation 

 in abundance and destructiveness of this louse in different seasons. 



Because of the great difficulty in controlling the insect after the 

 leaves of the trees have become curled, the writer has undertaken 

 to learn if it is feasible to destroy it in other ways. An extensive 

 seri.-s of experiments in fumigation with the deadly hydro- 

 cyanic acid gas was conducted. In these experiments wo 

 used a large canvas tent, a large paper box and a s'-iall 

 air-tight wooden box constructed for such work. We will 

 not at this time give the detailed results of these ex- 

 periments but will indicate the lessons they taught. Detailed instruc- 

 tions for the use of this substance will be found on another page of 

 this report. (See index.) 



