No. 509] ECOLOGY OF INDIAN CORN PLANT 293 



contact being quite independent of the decree of the til 

 ness of such plant for its food; biographical adaptations 

 are those based on a correspondence between the life 

 history of the insect and its organic food supply, such 

 that the latter shall always be accessible in sufficient 

 quantity to meet the varying needs of the dependent in 

 sect at the various stages of its growth; and numerical 

 adaptations are the consequence of such an adjustment 

 of the rate of insect multiplication to the plants or ani- 

 mals of its food that only the unessential surplus of this 

 food shall be appropriated, leaving its essential maximum 

 product undiminished. 



These several classes of adaptations limit each other 

 variously, the most desirable food of an insect being that 

 which is found within the area common to all of them. 

 That is, the most important food plants of a vegetarian 

 species will be those which are well within its structural 

 capacities of discovery, access and appropriation; within 

 its physiological powers of easy digestion and profitable 

 assimilation; and within its habitual range and location; 

 and which are consistent with its usual preferences and 

 habits of action, and are well adapted to furnish con- 

 tinuously amounts of food answering to its varying neces- 

 sities during the different stages of its life. 



Advantages of Biographical Adaptation 

 It is obviously to the advantage of any insect species 

 that it shall have its largest possible food supply coin- 

 cident with its own largest demand for food— that is, at 

 the climax of its period of growth. In a species restricted 

 to one annual food plant the most favorable relation will 

 usually be that in which the life history of the plant and 

 that of the insect coincide, the egg-laying period of the 

 one corresponding to the seeding period of the other, the 

 hatching of the insect being virtually simultaneous with 

 the germinating period of the plant, and the period of 

 most rapid growth being coincident in both. This kind 

 of adaptation is well illustrated by the life histories of 



