Twelfth Report of the State Entomologist 341 



back. Watch the gradual but rapid expansion of the wings, as they 

 grow before your eyes — the two membranes of which they are com- 

 posed steadily distending as the circulation from the body is forced into 

 the veins that lie between. The innumerable wrinkles of the mem- 

 branes are smoothed out; the scales that are implanted in them also in- 

 crease in size, until within perhaps half an hour the wings have assumed 

 their full development, and display their perfect ornamentation, in pat- 

 terns resulting from the combination of nearly half a million of individ- 

 ual -scales — the most delicate imbrication that may be found in nature, 

 and far surpassing any thing that art can produce. 



If not deterred by my long recital you will undertake what I have 

 proposed — to follow out the life-history of one of our silk-worms, and 

 having done so, if you do not find that the study has been one of surpass- 

 ing interest, leading you to further study of the kind, and wedding you 

 to entomology — then you have been given or have acquired a nature 

 that I can not comprehend. 



IV. The Practical Importance of the Study, 



It is universally conceded that Agricultural pursuits form the basis of 

 National prosperity, and that upon the products of the soil our existence 

 is dependant. 



The existence of the insect world also depends upon vegetable life : 

 hence arises that constant antagonism of man to the insect world, which 

 becomes so intensified when through his agency as a cultivator of the 

 soil, there results excessive multiplication of injurious species preying 

 upon crops which he deems essential to him. 



Every crop grown is exposed to their attack. It has been estimated 

 that there are upon an average, six species of attacking insects to each 

 known plant. From their minute size and the secrecy of their depreda- 

 tions, we can not fence them out, as we do our large domestic animals. 

 Probably there is no cultivated crop which is not lessened by one-tenth 

 through insect injury. Often there is a diminution in yield of one fourth; 

 frequently of one-half, and at times there is a total loss, as when during 

 the prevalence of the wheat-midge, forty years ago, entire fields of wheat 

 were left uncut in New York and other of the wheat states, and for a 

 term of years wheat could not be grown. In one year, in our State 

 .(1S54), the loss from this tiny insect was calculated at fifteen millions of 

 dollars. Illinois suff"ered in a single year, in its wheat and corn crops, to 

 the amount of seventy-three millions of dollars, according to estimate, 

 from the ravages of the chinch-bug {Blissus lencoptenis). True, these 

 were exceptional years, but from another insect pest, the cotton-worm 



