which this conspicuous protective structure clefeiuls the soft young 

 kernel those of insects are to be taken into account 



There are also, of course, many insect species, even among those 

 which habitually frequent the plant, which are unable to appropriate 

 certain parts of its substancje to their use, but this is because of the 

 absence ot adaptation on their part and not because of any special 

 defensive adaptation on the side of the plant. The adult or beetle of the 

 corn ^oot-worm {Diahrotica longicornis) is an example. The larva of 

 this insect feeds only on the roots of corn, and the beetles consequently 

 all make their first appearance for the year in corn fields, and find their 

 food at first on the corn plant. Owing, however, to the weakness of 

 their jaws they are unable to eat the leaves of corn, and feed only on the 

 fallen pollen and the young silks just growing out from the husks. Later, 

 as the pollen disappears and the silk dries up, they are driven to other 

 plants, or even compelled to leave the field entirely in search of food, 

 and hence are found at that time on clover heads and on the flowers of 

 thistles and ragweed and other late-blooming plants. 



Thus we may say that with the exception of the ear the whole plant 

 lies open and free to insect depredation, and that it is able to maintain 

 itself in the midst of its entomological dependents only by virtue of its 

 unusual power of vigorous, rapid, and superabundant growth. Like 

 every other plant which is normally subject to a regular drain upon its 

 substance from insect injur}-, it must grow a surplus necessary for no 

 other purpose than to appease its enemies; and this, in a favorable season, 

 the corn plaiit does with an energetic profusion vmexampled among our 

 cultivated plants. Insects, indeed, grow rapidly as a rule, but soon 

 reach their full size. Many species multiply with great rapidity, but 

 even these the corn plant wall outgrow, if given a fair chance, provided 

 they are limited to corn itself for food. 



The great injuries to corn by insects are done b}^ species w'hich come 

 into it from other and earlier crops; insects Avhich are in the full tide of 

 their multiplication, or perhaps at their maximum number for the season, 

 while the corn plant is still small and young. It is not the corn root- 

 aphis which injures corn most seriously, although confined to the corn 

 plant and endowed with a power of multipHcation scarcely surpassed 

 among insects; it is the chhich-bug, which breaks into the field of young 

 corn from adjoining wheat or oats, where it has already increased a 

 hundred-fold since spring began ; it is the army-worm or the cutworms, 

 or the wireworms, or the white-grubs, which began anil got most of their 

 growth in grass, and now, by their numbers and voracity, overwhelm 

 the young corn before the time of its most rapid growth has arrived. 

 Practically limited to this vigor of growth as a means of escape from 

 insect attack, anything which checks or retards its growth for a consid- 

 erable time has, of course, the effect to increase insect injury. Thus, 



