30 ASSOCIATION OF ECONOMIC ENTOMOLOGISTS. 



less appropriate fertilizers, some part at least of the substances which 

 they remove from them in their crops, while they are but little accus- 

 tomed as yet to shape their farm management or to vary their agri- 

 cultural practices in a way deliberately to avoid insect injuries. 



It is the more difficult to meet because each can act for himself in 

 respect to the fertilization of his land, uninfluenced and unharmed 

 by the indifference or ignorance of his neighbor, while the insects 

 bred by any farmer in a community are likely to infest the farms of 

 all, and finally, if continuously ignored, to become generally de- 

 structive, like an epidemic of disease. This epidemic condition has, 

 in fact, already been reached in certain considerable neighborhoods 

 of Illinois, and no doubt in other of the corn-growing States as well ; 

 neighborhoods measured by hundreds and thousands of acres, where 

 injuries by the corn root-aphis, the corn root- worm, and the common 

 white-grubs have steadily increased until they bid fair to become 

 permanent factors of the situation unless general measures are taken 

 for their control. 



The most immediately dangerous of these insects at the present time 

 is the corn root-aphis, which has shown a destructive capacity in 

 recent years easily understood when one knows its life history and 

 ecology. It will be a scandal and a reproach to the American farmer 

 and to the American entomologist if we allow to grow up under our 

 eyes so great and permanent an enemy to corn culture as this insect 

 is capable of becoming, and we ought to raise an earnest voice of 

 warning, instruction, and advice while the difficulty is still local and 

 the insect still controllable. 



This aphis was first recognized in 1862 by Walsh, who reported at 

 that time that a farmer at Rock Island, 111., had discovered, toward 

 the last of May, minute insects in prodigious numbers on the roots of 

 corn in one of his fields, and that they had apparently destroyed from 

 a half to three-quarters of the crop so far as to necessitate replanting. 

 Walsh, visiting the field a fortnight later, obtained many wingless 

 specimens, from which he bred 15 winged females. He noticed many 

 small brown ants among the roots of the corn infested by the aphis, 

 and inferred by analogy an association of the usual form between 

 these two insect species. I first began to study this aphis in 1883, 

 and virtually all the facts now known concerning its life history, 

 ecology, and economic relations have been made out at my office in 

 Illinois by myself and my various assistants. 



THE LIFE HISTORY OF THE APHIS. 



The life history of the corn root-aphis is in no way peculiar. All 

 the main features of it have been repeatedly published and are doubt- 

 less sufficiently familiar to all; and I have to report under this head 



