THE CORN ROOT-APHIS AND ATTENDANT ANT. 39 



rule to a single year; early, deep, and thorough preparation of the 

 soil for corn, with a diligent use of the disk harrow after the ground 

 is plowed, and general measures for the maintenance and increase 

 of soil fertility, are the chief features of this routine. It is better 

 that the land should lie a day or two between successive diskings, 

 and careful advantage should be taken of cold, beating rains to disk 

 the land as soon thereafter as it is fit to work. If to this we add early 

 and continuous cultivation of the crop, as deep in the beginning as the 

 corn will stand, and if we further advise that corn should never, 

 in any event, be grown on land known to have been infested by this 

 insect the year before, wo shall have done all that our present knowl- 

 edge of this aphis and its attendant ant will warrant. 



It is of course also to be understood that each farmer has in his 

 hands, in considerable measure, the interests of his neighborhood, 

 and that no man should be permitted to raise on his own land, by rea- 

 son of his negligence, insects which will spread to the property of 

 others to their serious injury. The moral and legal principles whose 

 growing recognition we owe to the introduction and spread of the 

 San Jose scale apply just as forcibly to the insect and fungous pests 

 of general agriculture, and some day, I do not doubt, they will be 

 just as thoroughly enforced. 



Mr. Burgess asked when, in the case of the field culture experi- 

 ments, the counts of aphides remaining alive were made. Mr. Forbes 

 answered, as soon after the experiment as it was believed that the 

 ants and aphides had established themselves; usually this was in 

 about a week, but it was sometimes delayed by bad weather. 



Mr. Morgan asked if any relation had been discovered between the 

 rate of multiplication of the aphis and the vitality of the corn plants, 

 as influenced by soil or climatic conditions. 



Mr. Forbes answered that no experiments had so far been made 

 for this purpose, but that some were planned. 



Mr. Morgan said that he had observed that whenever cool nights 

 come on, lowering the vitality of the plant, the common cotton aphis 

 is more abundant. 



Mr. Quaintance had observed that they were more abundant dur- 

 ing late spring and also in early fall than during the summer. 



Mr. Morgan observed further that in new fields cotton was little 

 affected, but on worn-out ground aphides were abundant. Had this 

 been observed in relation to the corn root-aphis in Illinois corn lands ? 



Mr. Forbes replied that in that part of Illinois in which the corn 

 root-aphis is abundant it is difficult to find worn-out corn land, and 

 that the condition referred to had not been observed. 



