HEMIPTERA. 
263 
pearance and use from the mouth of gnawing insects, 
it is found to be composed of the same or correspond- 
ing parts, with the exception of the palpi, which are 
quite obsolete. These parts, however, have, of course, 
undergone great modifications, to such a degree, in- 
deed, that it is exceedingly difficult to recognise them. 
It is only from their insertion and position relatively 
to each other, that any agreement can he inferred ; 
and, at most, the oral organs of suctorial species can 
only be considered as analogous to or representative 
of the parts of a mouth formed for mastication. There 
is reason to believe that some of the ingenious ob- 
servers, who have turned their attention to this sub- 
ject, have carried their views rather too far, from a 
wish to demonstrate a certain uniformity of organisa- 
tion among different tribes — an interesting inquiry, 
but one which requires to be pursued with great 
caution, as the fancy is so apt to lead us astray. At 
all events, we have been often led from this cause 
to the application of names, which, however signifi- 
cant as originally used, becomes quite inappropriate 
in their present extended acceptation. The term 
mandibles, for example, is sufficiently descriptive of 
the gnawing organs of the mandibulata, but is wholly 
unmeaning when applied to a slender filet composing 
a portion of a tube, in which both the form and the 
function are completely changed. 
The rostrum, when not employed, is bent beneath 
the breast, to which it is closely applied, passing be- 
tween the legs. It consists of four joints, generally 
distinctly marked, of a cylindrical form, or tapering 
