THE OUTBKEAK 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 this 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. 
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Yig. 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 tins bureau, however, has specimens in his collection from 
Illinois, taken in 1886. 
During Xovember 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 
