FARMERS' INSTITUTES. 431 



DESTRUCTION OF INJURIOUS INSECTS. 



BY PROF. A. J. COOK. 

 [Ueliverea at Howell and Oentreville Institutes.] 

 EXTENT OF INSECT DEPREDATIONS. 



The subject of injurious insects, and the evil they do is indeed a portentous 

 one, nor is it comforting to be told, though assuredly the truth, that the bar- 

 riers which these insidious foes are rearing in the way of successful agriculture 

 and liorticulture, are becoming annually more formidable. It would be diflS- 

 cult in all the long list of our farm and garden products to find a single one 

 that is wholly free from insect depredation, while many, and they often the 

 most important, have a score of insect enemies to sap their vitality or work 

 their utter ruin. It takes many millions of dollars eacii year to meet the 

 demands of these ravenous hordes. Hence the interest wliich all our farmers 

 wisely take in aught tliat relates to tlieir overthrow. 



Whether or not the art of agriculture is founded on science, surely economic 

 or practical entomology rests wholly on scientific research. The varied 

 economy in the structure, habits and transformations of insects makes pro- 

 longed study and wide knowledge imperative to the practical entomologist. 

 A very considerable factor of this knowledge is based wholly on field work — 

 long, hard, accurate observation of the insects in their native haunts when 

 they are actually working their mischief. 



DIFFICULTY OF THE STUDY. 



Again, our insect enemies are counted by the thousands, and that practical 

 knowledge requisite to successfully combat their noxious work demands large 

 libraries, costly apparatus and prolonged study. In view of the extent and 

 intricacy of this subject, no less than its practical importance, I have planned 

 to formulate in this paper that part of our practical knowledge which bears 

 directly on the remedy and cure for insect depredations, in the hope that it 

 might assist the farmer and fruit grower to work intelligently and efficiently, 

 even though they possess but a limited knowledge of the insects themselves. 



INSECT TRANSFORMATIONS. 



Most if not all of you know that insects are wondrously different in the suc- 

 cessive stages of their development from the egg to the mature state. How 

 seemingly wide apart are the maggot or larva of the meat fly, which so vexes 

 the good housewife ; the motionless, apparently lifeless seed-like pupa, and the 

 buzzing fly; yet all are but different stages of the self-same insect. Our cab- 

 bage butterflies experience equally striking transformations. The caterpillar 

 is green, wormlike and disgusting to the cook who attempts to prepare the 

 savory vegetable for the noon-tide meal. The chrysalis is gray, inactive, and 

 as it swings from its silken cord, would seem void of all possibility of future 

 mischief. The butterfly is white, dotted with black, graceful of motion as it 

 slowly wings its flight from garden to garden, and with its short sucking tube 

 and frail body, would seem little capable of the serious mischief which it 

 scatters with its tiny green eggs that it glues thick and wide to the cabbage 

 plants. 



