DESCRIPTION AND CLASSIFICATION OF INSECTS. 27 



weakened, they appear unjust even to those who feel them, at 

 the moment they are attacked by arguments which are inadmiss- 

 able ; but the next instant the proofs are forgotten, and the per- 

 verse association resumes its empire." 



34. During the last half century the low estimation in which 

 the science of entomology was formerly held, has been slowly 

 giving way to a more correct appreciation of its value and of the 

 benefits which a general study of its details might confer upon 

 mankind. At times like the present, when a vast province is 

 trembling at the prospect of one of its staple productions dwin- 

 dling away under the attacks of minute but numberless insects, 

 all are willing to listen to the teachings of the entomologist, and 

 would seek to elevate to the position of an invaluable science, the 

 study which, when proofs are forgotten, will probably be allowed, 

 in popular estimation at least, once more to subside into a harm- 

 less or frivolous pursuit. 



35. It would be an easy task to show by numerous illustra- 

 tions the great economical value of the science of entomology, 

 but as this would swell out the pages to too great an extent, I 

 shall content myself with a reference to the statistical facts in- 

 terspersed throughout this essay, which may serve to create, 

 where it is most needed, a proper appreciation of the magnitude 

 of those evils which are growing upon us, by the selfishness, in- 

 difference and neglect, which a mistaken impression of individual 

 security has cherished. 



36. Insects may be defined as animals without vertebrae ; six- 

 footed ; with a distinct head furnished with two antennae, and a 

 pair of compound immoveable eyes ; breathing through open- 

 ings which lead to internal air tubes or trachse ; sexes distinct ; 

 adult state attained through a series of changes called metamor- 

 phosis. 



37. Nearly every insect undergoes three changes, (fig. I., II. 



