455 



large as would be possible for all three taken together if they made tlieir 

 assault on the plant simultaneously. The advantage to both plant and 

 insects of this adjustment of life histories — if one may call it such — is 

 obvious at once. 



That some actual adjustment of larval periods has here been made is 

 rendered somewhat more probable by the fact that a closely related spe- 

 cies of Graphops which infests the wild primrose {Qinotlicra biennis) in 

 southern Illinois, has a life history different from that of the species 

 which breeds in the strawberry — hibernating as an adult, like Typoph- 

 orus, and not as larva, like the strawberry species of its own genus. 



M.\L.\DJUSTMENT OF COMPETITIONS 



The corn plant is in greater danger from insect ravage during the 

 first month of its life than at any later time. This is because it offers 

 then a comparatively scanty supply of food, so that a small number of 

 insects may work great destruction ; because the single small plant is 

 much more easily killed than a larger one ; and because a larger number 

 of active rival insects infest corn when it is young than at any other time. 

 some of them beginning with the recently planted or just sprouting seed. 

 The young roots, the underground part of the stalk, the stalk above 

 ground, and the leaves, both before and after they unfold, are all liable 

 to infestation by several species at the same time. The seed is injured 

 by the wireworms, the seed-maggot, the Sciara larva and the larva of 

 Svstcna blanda; the roots, by the wireworms, the root-aphis, the corn 

 root-worms, and the white-grubs ; the stalk under ground, by the wire- 

 worms, the root-aphis, the southern corn root-worm, and the bill-bugs ; 

 the stalk above ground, by the bill-bugs, the cutworms, the web-worms, 

 the stalk-borers, and the army-worm — sometimes by the chinch-bug also ; 

 and the leaves, by the bill-bugs, the web-worms, the cutworms, the army- 

 worm and the first generation of the ear-worm. 



This concentration of injury upon the corn when it is young is a 

 case of maladaptation, since the ])lant has least to off'er when it is most 

 heavily drawn upon. It will be noticed, however, that this early spring 

 attack is mainly delivered by insects which come into corn from some 

 other vegetation, chiefly from grass, and whose occurrence in the corn 

 field is scarcely more than accidental. The motive to an adjustment of 

 habits and life histories to the capacities of the plant is therefore virtually 

 wanting, and seems at any rate impossible, owing to the variability and 

 inconstancy of the several factors involved. 



COXCLUSION 



From the foregoing it will be seen that the corn plant is not only an 

 exotic in its origin, but that, aside from its relation to man, it still re- 

 mains an unnaturalized foreigner, not sufficiently adapted to our condi- 

 tions to survive without the constant supervision of a guardian and the 



