February, '09] JOUKNAL OF ECONOMIC ENTOMOLOGY 31 



worm would be compelled to seek its food in other and much less 

 abundant plants, the corn root-aphis would be limited to the compara- 

 tively sapless roots of the small field weeds; the cornfield ant would 

 have to forage mainly for its food, and the corn root-worm would 

 seemingly perish from off our area if it were not for the contributions 

 to their welfare made by man in the pursuit of his own ends. 



Similar incidental contributions of one group to the welfare of 

 another are seen in the relations of the weeds of the field in early 

 spring to the first seasonal appearance of the corn root-aphis, which 

 is dependent for its maintenance on these young weeds for as much as 

 a month before the com has begun to grow. This seasonal succession 

 of plants in the cornfield is thus a necessary condition to the existence 

 of the aphis there. On the other hand the corn root-worm could not 

 exist except for the continuance of corn in the same situation as a 

 member of the associate group year after year; and the corn itself 

 would fall a speedy victim to its enemies and competitors if it were 

 not regularly relieved from the consequences of its own incapacities 

 and its failures of adaptation by the interested aid of man. We have 

 so cherished and protected this plant for untold generations that it 

 is permanently fixed in a state of infantile helplessness, incapable of 

 independent competition with the other plants of its association, and 

 about as defenseless against insect attack as is a flock of sheep against 

 a pack of wolves. By the constant interference of our planting and 

 our cultivating processes, and by our selection of characters which 

 adapt the plant to our needs, to the neglect of those which might make 

 it independent of our care, we have wholly prevented all spontaneous 

 adaptation of the corn plant to the conditions of its own maintenance, 

 and it has hence made no progress towards independent life during all 

 the centuries or millenniums of its residence in our territory. 



I have wondered if. in this respect, we might not improve our se- 

 lection by sometimes giving the preference, in saving seed, to those 

 plants which have best withstood unfavorable conditions, instead of 

 making our choice, as we now invariably do where we choose at all, 

 from among the plants which have succeeded best where all the con- 

 ditions have been favorable. I would like to see the experiment made 

 of growing corn from seed taken from the few best stalks of a field 

 which has been overrun by insects, in the hope that we might thus 

 gradually develop varieties of this plant capable of withstanding insect 

 attack, or of selecting our seed from the best grown and most fruit- 

 ful plants in a field which has suffered heavily from drouth — of ap- 

 plying, in short, the method by which rust-resistant varieties of wheat 

 and the like are now being formed. 



