No. 509] ECOLOGY OF INDIAN CORN PLANT 



Aphis makliradicis, the so-called com root-aphis, is not 

 especially different in adaptive characters from the other 

 root-lice generally, and it lives, indeed, in early spring, 

 on plants extremely unlike corn. Finding its first food 

 on smartweed (Polygonum), and on the field grasses 

 (Setaria, Panicum, etc.), it is scarcely more than a piece 

 of good fortune for it and for its attendant ants if the 

 ground in which it hatches is sometimes planted to corn, 

 in which it finds a more sustained and generous food- 

 supply than in the comparatively small, dry and slow- 

 growing plants to which it would otherwise be restricted. 



The larva of Diabnrfica loiuiuomis, usually known as 

 the corn root-worm, is, of course, well constructed to 

 burrow young corn roots, but it differs from related 

 Diabrotica larvae in no way that I know of to suggest a 

 special adaptation to this operation, except in the mere 

 matter of size. If it were larger it would probably eat 

 the roots entire, as does the closely related and very 

 similar larva of D. 12-punctata, Indeed, there is some 

 reason to believe that D. longicumis may breed in large 

 swamp grasses, since the beetle has been found abundant 

 in New Brunswick in situations where it is difficult to 

 suppose that it originated in fields of corn, and where 

 such grasses are extremely common. Even the special 

 corn insects seem, in short, structurally adapted to much 

 more general conditions than those supplied by the corn 

 plant alone, and if they are restricted largely or wholly 

 to this plant for food, this seems due to other conditions 

 than those supplied by special structural adaptations. 



In short, in the entomological ecology of the coi n plant 

 we see nothing whatever of that nice fitting of one thing 

 to another, specialization answering to specialization, 

 either on the insect side or on that of the plant, which 

 we sometimes find illustrated in the relations of plants 

 and insects. The svsteni of relations existing in the corn 

 field seems simple, 'general and primitive, on the whole, 

 like that which doubtless originally obtained between 

 plants in general and insects in general in the early stages 

 of their association. 



