20 INSECTA. 
extracting fluids by suction; the attenuated stylets of which 
the sucker is formed, pierce the vessels of plants and animals, 
and the nutritious fluid being successively compressed is 
forced into the internal canal, and thus arrives at the eso- 
phagus.. The sheath of this apparatus is at these times fre- 
quently bent into an angle, or becomes geniculate. These 
Insects, like other Suctoria, are furnished with salivary ves- 
sels(1). , 
In most of the Insects which compose this order, the elytra 
are coriaceous or crustaceous, the posterior extremity being 
membranous and forming a sort of an appendage to them; 
they almost always decussate; those of the other Hemiptera 
are simply thicker and larger than the wings, semi-mem- 
branous, like the elytra of the Orthoptera, and ‘sometimes 
opaque and coloured, sometimes transparent and veined. 
There are a few longitudinal plice in the wings. 
The composition of the trunk begins to experience modifi- 
cations which approximate it to that of the Insects of the fol- 
lowing orders. Its first segment, hitherto designated by the 
name of thorax, has, in several, much less extent, and is in- 
corporated with the second, which is equally exposed. 
Several have simple eyes, of which, however, there are 
frequently but two. 
The Hemiptera exhibit the same forms and habits in their 
three states. ‘The only change they experience consists in 
the development and growth of the volume of the body. They 
usually have'a stomach with firm and muscular parietes, 
a small intestine, followed by a large one divided into several 
inflations, and biliary vessels, few in number, and inserted at 
a distance from the pylorus. 
I divide this order into two sections(2). 
In the first, that of the HETEROPTERA, Lat., the rostrum 
me 
(1) See in particular the pao eacal observations of M. Leon Dufour, on the 
Cicade and Nepe. 
(2) In the systems of Messrs Kirby and Leach, they form two orders. Our 
Heteroptera are there termed Hemiptera, and our section of the Homoptera forms 
the second under the same name. 
