xii INTRODUCTION 



lete, a fate which overtook the cochineal insect. The latter 

 was formerly far more important as a source for carmine and 

 the red dyes made therefrom, but has been replaced by in- 

 ferior, though more cheaply produced chemical colors. 



Few other insects are directly useful to an extent that 

 makes them of general economic importance, and so much 

 has been written of the species just mentioned that they are 

 omitted from the following account. It is confined to those 

 insects which bear a less pleasant relation to man and to 

 those which are secondarily beneficial in so far as they may 

 regulate the abundance of the primarily destructive species. 



For convenience we may group insects in their relation to 

 human welfare, into several categories as has been done in 

 the following chapters. In their association with various 

 diseases of man and of the higher animals, insects are of very 

 direct importance and this aspect stands more or less clearly 

 apart from the others. As enemies of various cultivated 

 plants, the depredations of insects are of importance in so far 

 as they interfere with agricultural production, decreasing 

 the supply of foods and of other less necessary although 

 valuable materials. Their influence upon the forests is similar 

 to the last in many ways, but as will appear on closer exami- 

 nation presents different problems from the practical stand- 

 point. 



Many insects, some of them of far less real importance than 

 some of their less sociable fellows, will be considered under 

 the caption of household insects. These creatures, of many 

 diverse sorts, have taken up their abode with man and are 

 continually intruding themselves upon his attention. Some 

 are dealt with elsewhere as they are related to diseases or 

 have otherwise striking economic relations; the remainder, 

 no worse than nuisances, show many interesting and sur- 

 prising adaptations. 



