Bugs, Cicadas, Aphids, and Scale-insects 165 



in the insects of complete metamorphosis. With similar mouth-parts the 

 young have, in most cases, similar feeding habits, preying on the same kinds 

 of plants or animals that give nourishment to the parents. 



The extent of the injuries done by various members of this order to 

 farm and orchard crops, to meadows and forests, and to our domestic 

 animals is enormous. Of the other insects the order of beetles includes 

 numerous crop pests, and the caterpillars of many moths and a few butter- 

 flies do much damage; locusts have a healthy appetite for green things, 

 and many kinds of flies could be lost to the world to our advantage, but 

 perhaps no other order of insects has so large a proportion of its members 

 in the category of insect pests. The single Hemipterous species, Blissus 

 leucopterus, better known by its vernacular name of chinch-bug, causes 

 an annual loss to grain of twenty millions of dollars; the grape phylloxera 

 destroyed the vines on 3,000,000 acres of France's choice vineyards; the 

 San Jose scale has in the last ten years spread from California to every 

 other state and territory of the United States and become a menace to the 

 whole fruit-growing industry. So, despite their small size and their general 

 unfamiliarity to laymen, the Hemiptera are found by economic entomologists, 

 in their warfare against the insect-scourges of the country, to be one of the 

 most formidable of all the insect orders. 



The classification of the Hemiptera into subgroups is a matter likely 

 to prove difficult for the amateur and general collector. The order as repre- 

 sented in our country includes thirty-nine families, and the structural char- 

 acters separating some of these families are slight and not easily made out by 

 untrained students. For the use, however, of readers of this book capable 

 of using them, keys or tables of all the families of the Hemiptera are presented. 

 For more general use, however, I shall try to arrange the families in groups 

 depending on the habits and more obvious appearance and make-up of the 

 insects, characteristics which may be readily noted. And this arrange- 

 ment will not be less "scientific" than the arrangement in the key com- 

 monly used by entomologists, as the latter is confessedly largely artificial 

 and convenient rather than natural in its groupings. 



The order is separable into three primary natural groups or sub-orders 

 as follows: 



Wingless forms, with a fleshy, unsegmented sucking-beak, living as parasites on 



man and other mammals PARASITA. 



Winged, or sometimes wingless, but always with the beak segmented. 



Wings of the same texture throughout and usually held sloping or roof-like 

 over the back and sides of the body; sucking-beak arising from the 

 hinder part of the lower side of the head; tne head so closely joined 

 to the prothorax that the bases of the fore legs touch the sides of the 

 head . . HOMOPTERA. 



