80 M. A. Vayssiére on the 
metathorax, which are closely soldered together and present 
in their middle an inflated portion, a sort of lozenge-shaped 
plate; this plate is divided, in the direction of the length of 
the body, into two equal and symmetrical parts, each of which 
presents on its inner margin a rather deep notch (which, 
however, does not go very far), and then posteriorly an emar- 
gination. On the lateral parts of this plate there are a series 
of nodosities and folds, symmetrically arranged on the two 
sides of the body, and serving as points of insertion for the 
wings; I think it would be tiresome to enter here into the 
description of these nodosities, and I shall only say a word or 
two about them further on in speaking of the wings. 
The ventral surface of the thoracic region (fig. 8) shows im 
front the prothorax distinctly separated from the rest; upon 
the somewhat lateral parts are the points of insertion of the 
first pair of legs. ‘These are separated. from each other only 
by a rather wide prominence of a strong reddish-brown colour. 
A portion of the mesothorax is distinct on this surface, 
although its lower two thirds are intimately united with the 
metathorax. The insertions of the legs of the second and 
third pairs upon the thorax are placed almost upon the sides 
of a large strongly chitinized plastron, which of itself consti- 
tutes the lower surface of this region of the body. 
The abdomen remains to be mentioned. On the dorsal 
surface (fig. 7) this presents ten well-marked segments, ex- 
cept the first, of which the anterior margin is confounded 
with the metathorax; but on the ventral surface (fig. 8) it only 
exhibits eight, the boundaries of the first two having com- 
pletely disappeared, and their union with the thoracic region 
being as intimate as possible. 
The segments of the abdomen are not all of the same form 
and the same dimensions. ‘Thus, when seen from the dorsal 
surface, the second, third, fourth, and fifth segments repre- 
sent in form each a very wide trapezium; the sixth shows 
the same form, but reversed, the large base or lower base of 
the trapezium being in front, while the superior base is 
behind ; it is also much longer than the preceding, but not so 
wide. The seventh and eighth segments are nearly rect- 
angular, while the ninth presents the appearance of a reversed 
trapezium, of which the small base is much emarginate; finally, 
the last abdominal segment, that which bears the sete, nearly 
forms a square. 
These various segments, which are more convex on their 
dorsal than on their ventral surface, are not, however, all 
equally so; thus the sixth segment is a little more inflated 
than the preceding ones, and the ninth much more so. 
