Flemiptera-Fleteroptera. 7 
appreciating which the central lobe is, and it seems to me 
open to doubt as to which may be the true clypeus; the 
external lobes are the gens or cheeks; from beneath the 
central lobe extends the labrum which is closely adpressed 
over the base of the rostrum; this latter organ springs 
from the underside of the head, which is excavated so as 
to receive its first joint in repose; when the rostrum is 
stretched out, the cavity will be seen to be covered by a 
sort of muscular membrane, and to the front of this mem- 
brane the rostrum is attached ; it is usually three or four 
jointed, and is structurally a sheath open at the apex in 
which the four sete lie which are considered to represent 
the mandibles and maxillew; the sides of the sheath fold 
over in front and almost or quite touch along a straight 
suture, so as completely to cover up the sete, which can be 
drawn out if necessary. The palpi of the other orders seem 
to be unrepresented here ; in repose the rostrum generally 
lies adpressed to the sternum and sometimes even reaches 
beyond the centre of the abdomen, but in some genera it is 
short and bent at the base as in Salda, Reduvius, etc., so 
that it does not lie adpressed to the underside; it can 
be extended by means of the basal membrano-muscular 
hinge. 
The Thorax.—This, as in other insects, is composed of three 
segments, the prothorax, mesothorax and metathorax, the 
upper surfaces of which are termed respectively the pro- 
notum, mesonotum and metanotum, and the under, proster- 
num, mesosternum and metasternum ; the sides of the stern- 
ites are called the pleure; the pronotum throughout the 
family is very largely developed and extends backwards to 
the base of the elytra and scutellum which it frequently more 
or less covers; it varies very greatly in form and is often 
constricted in front intoa collar or a callose margin ; the pro- 
sternum receives the anterior pair of legs, and the position 
of the acetabula or sockets into which the legs articulate 
is of considerable value in classification; the mesonotum 
