THE OUTBREAK OF 1890. 



19 



Mexico almost to the Pacific Ocean. It has not actually been found 

 in Mexico and no one has searched for it there. Wheat in Mexico is 

 said to have been injured by a " green louse," and it is reasonable to 

 suppose that the insect may occur far to the southward of its present 

 known range of distribution. Its entire absence from eastern Canada 

 and northeastern United States, except in eastern Massachusetts near 

 Boston, where it seems to have been found by Mr. Paul Hayhurst in 

 September, 1908, will be noted. 



THE OUTBREAK OF 1890. 



(Fig. 5, p. 20; Diagram II, p. 21.) 



Up to the year 1890 in tins country the very destructive nature of 

 this insect had not yet become apparent ; hence it had not received the 

 close attention that, as we now understand, it justly deserves. 



Fig. 4. — Map showing the known distribution of the spring grain-aphis in the United States and Canada. 



(Original.) 



While the senior author was and had been engaged in grain-insect 

 investigations in Indiana during the six years following its discovery 

 by him at Oxford, the species was not looked upon as one of those 

 deserving especial attention; therefore from 1884 to 1889 no notes 

 were made upon it, and no references to it are to be found in the 

 correspondence of the Division of Entomology. Mr. J. T. Monell, 

 now of this bureau, however, has specimens in his collection from 

 Illinois, taken in 1886. 



During November and December, 1889, the insect was again 

 observed in such abundance in fields of young wheat about Lafayette, 

 Ind., as to attract the attention of the senior author, who found it 

 repeatedly on young wheat in the fields during the entire winter. 

 The influences of mild or high temperatures during winter, especially 



