28 



Mr. F. H. Chittenden has estimated, from experiments re- 

 cently conducted by him in Washicgton, that in the warmest 

 weather the liie cycle is about five weeks. In my experimental 

 work during midsummer, under the most favorable C(mditions, 

 in California and Illinois, I have been unable to get a full grown 

 larva in less than five weeks from the time it emerged from the egg. 



The number of annual broods of ihis insect depends largely 

 upon the geographical location and upon the condition of the 

 mill. In California, where the climate is even, the amount of 

 damage done and inconvenience caused varies but little with the 

 time of J ear. In the Eastern States, however, the insect is most 

 troublesome during the summer months; alttiough in exceptionally 

 warm mills it is very annoymg even in midwinter. I have shown 

 by a series of carefully planned experimentn that there are from 

 five to six annual broods in California, and probably the same 

 number in some of the Southern States and in Eastern States where 

 the mills are well heated during the winter months. In most 

 cases, however, in the East, four broods seem to be the average, 

 appearing most abundantly from April to December. Brood after 

 brood h^ve appeared successively in my cages for the past two 

 years. 



From a long series of experiments, I have selected five repre- 

 senting the life cycle of this insect, the eggs being deposited in 

 April, August, and October. The results are given in the follow- 

 ing table: 



