HEMIPTERA. 157 



come much nearer to them, than to any other insects, in structure 

 and habits. Bugs, Hke other insects, undergo three changes, but 

 they retain nearly the same form in all their stages ; for the only 

 transformation to which they are subject, from the young to the 

 adult state, is occasioned by the gradual development of their 

 wing-covers and wings, and the growth of their bodies, which 

 make it necessary for them repeatedly to throw off their skins, to 

 allow of their increase in size. Young, half-grown, and mature, 

 all hve in the same way, and all are equally active. The young 

 come forth from the egg without wing-covers and wings, which 

 begin to appear in the form of little scales on the top of their 

 backs as they grow older, and increase in size with each succes- 

 sive moulting of the skin, till they are fully developed in the full- 

 grown insect. 



The Hemiptera are divided into two groups, distinguished by 

 the following characters. 



1. Bugs, or True Hemiptera {Hemiptera heteroptera) , in 

 which the wing-covers are thick and opake at the base, but thin 

 and more or less transparent and wing-like at the tips, are laid hor- 

 izontally on the top of the back, and cross each other obliquely at 

 the end, so that the thin part of one wing-cover overlaps the 

 same part of the other ; the wings are also horizontal, and are not 

 plaited ; the head is more or less horizontal, and the beak issues 

 from the forepart of it, and is abruptly bent backwards beneath 

 the under-side of the head, and the breast. Some of the insects 

 belonging to this division live on animal, and others on vegetable 

 juices. 



2. Harvest-flies, Plant-lice, and Bark-lice {Hemip- 

 tera homoptera), in which the wing-covers are, as the scientific 

 name implies, of one texture throughout, and are either entirely 

 thin and transparent, hke wings, or somewhat thicker and opake; 

 they are not horizontal, and do not cross each other at their ex- 

 tremities, but, together with the wings, are more or less inclined 

 at the sides of the body, like the wing-covers of locusts ; the face 

 is either vertical, or slopes obliquely under the body, so that the 

 beak issues from the under-side of the head close to the breast. 

 All the insects included in this division, live on vegetable 

 juices. 



