THOEACIO REGION. 
19 
or Mesqnotum. It is usually large in the winged forms, 
which exhibit the upper surface chiefly occupied by the 
Scutum. Here three conspicuous coriaceous lobes 
appear, of which the two lateral give support to the 
muscles of the first pair of voluminous wings. Between 
them, and a little in advance, a third lobe is seen, 
which may be the representative of the Prces-cutum. 
The Scutellum is somewhat triangular in shape, 
and is placed posterior to the two lateral lobes. 
The Mesosternum is deeply excavated, to receive the 
folded rostrum, and on each side the fulcra occur, 
belonging to the second pair of legs. 
The third segment, called Metathorax or Metanotum, 
is rather inconspicuous. It supports, above, the hinder 
pair of wings, and below, on the Metasternum^ are 
placed the fulcra for the third pair of legs. 
THE ABDOMEN. 
# 
This part of the body is composed of several rings, 
and is capable of much distention. On this account the 
insect presents very different outlines, according to the 
varying amounts of fluid nourishment it contains. The 
dorsal and ventral rings are laterally united by the 
yielding folds of the Gonnexivum, which by its corruga- 
tions gives rise to a puckered edge or carina, that 
becomes more and more obvious as the insect shrinks 
by being stinted in its food. On the other hand, the 
insect may be so fully fed that the Dorsum becomes 
domed and shining, simply from distention. 
The number of rings most easily distinguished in 
the abdomen is nine, but theoretically it is eleven. 
Perhaps the want of agreement among naturalists, as to 
the typical number of Somites in Inseota, is caused by 
the discordant views entertained as to the composition 
of the insect head. 
Whilst some would make the head but a single 
