168 INSECTS INJURIOUS TO VEGETATION. 



but having the wing-covers sometimes entirely transparent, 

 and sometimes more or less opake, and these, by most ento- 

 mologists, are also classed among Hcmipterous insects, because 

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

 structure and habits. Bugs, like 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 develop- 

 ment 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 live 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 successive 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 horizontally 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 hori- 

 zontal, and the beak issues from the fore part 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 (Hemiptera 

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

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

 and transparent, like wings, or somewhat thicker and opake; 

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

 extremities, but, together with the wings, are more or less in- 

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

 the face is either veitical, or slopes obliquely under the body. 



