2G2 
SYSTEMATIC ARRANGEMENT. 
important character of having a sucking instrument 
with a jointed sheath, and it must be admitted to be 
.highly inadvisable to multiply orders except for the 
most urgent reasons. But if rejected as primary 
groups, they must be adopted as secondary ones ; and 
we shall accordingly follow Latreille, who has, from 
this circumstance, divided this order into two great 
sections, which he denominates Heteroptera (wings 
of different texture) and Homoptera, (-wings of uni- 
form texture.) 
The under wings are usually not of large size, and 
offer nothing peculiar in their forms and composition. 
When at rest they are covered by the liemelytra, 
being simply drawn beneath them, and more or less 
crossed, but without forming distinct longitudinal or 
transverse folds. Several species of Hemiptera are 
entirely apterous. 
This is the only order in which upper wings of a 
rigid consistency coexist along with a mouth formed 
for sucking. The latter differs considerably from the 
spiral tube of butterflies and moths, which is a mere 
canal for conveying the nutritive fluids into the eso- 
phagus ; besides serving this purpose, it is so formed 
that it acts as a lancet for piercing the integuments 
of plants and animals. As great length would scarcely 
be compatible with such a usage, it seldom equals the 
dimensions of a lepidopterous proboscis, being usually 
much shorter than the body. There are a few ex- 
ceptions to this rule, however, and in some examples 
it is so long as to project a good way behind the body 
like a caudal filament. Although so different in ap- 
