334 
INSECTA. 
prothorax and mesothorax, the ternary division once established, 
naturally presented itself to the mind, and the celebrated professor 
Nitzsch was the first to employ it. Some naturalists have since desig- 
nated the prothorax or anterior segment, that which bears the two 
first feet, by the term collar, collare. Wishing to retain the deno- 
mination of corselet, but to restrain its application within proper 
limits, we will employ that term in all those cases where this seg- 
ment is much larger than the others, and where these latter are join- 
ed to the abdomen, and seem to constitute an integral part of it — a dis- 
position proper to the Coleoptera, Orthoptera, and several of the 
Hemiptera. When the prothorax is short, and forms with the suc- 
ceeding segments a common and exposed mass, the trunk composed 
of the three will retain the name of thorax. We will also continue 
to ^ty\e pectus the inferior surface of the trunk, dividing it according 
to the segments, into three areae, the ante-pectus, medio-pectus, and 
post-pectus. The median line will also constitute the sternum, which 
we divide into three parts : the ante-sternum, medio-sternum, and 
post-sternum. 
The teguments of the thoracic segments, as well as of those of the 
abdomen, are usually divided into two annuli or semi-annuli, the one 
dorsal or superior, the other inferior, laterally united by a soft and 
flexible membrane, which, however, is but a portion of the same 
tegument that in many Insects, the Coleoptera particularly, is less firm. 
At the point of junction between these annuli we observe a little 
space of a more solid texture, or of the consistence of the annulus 
itself, which bears a stigma, so that the sides of the abdomen jjresent 
a longitudinal series of small pieces, or each segment seems to be 
quadripartite. Other equally corneous pieces occupy the inferior 
sides of the mesothorax and metathorax and immediately under the 
origin of the elytra and wings, which are supported by another longi- 
tudinal piece. The relations of these parts, the size and form of the 
first joint of the coxae, the manner in which they are articulated with 
wings are inserted. It is also fornaed of that portion of the thorax w'hich extends 
backwards to the origin of the abdomen, a circumstance w'hicli evidently demonstrates 
the position of the two last stigmata of the trunk, they being placed on the sides of 
this extremity, behind the wdngs, and above the last pair of legs. I am even of 
the opinion that this observation will apply to all winged Insects. Their metathorax 
should be divided, at least above, into two parts or semi-segments, one, in the 
Tetraptera, bearing the second wings and destitute of stigmata, and the other fur- 
nished with them ; sometimes this latter portion, as in nearly all Insects, the Hyme- 
noptera with a pediculated abdomen, the Rhipiptera and Diptera excepted, appears 
to belong to abdomen sometimes it is incorporated with the trunk or thorax and closes 
it posteriorly, as in those last mentioned. In the Orthoptera, Hymenoptera, Lepi- 
doptera and Diptera, the two anterior or thoracic segments are placed between the 
prothorax and the mesothorax. The abdomen will then consist of nine complete seg- 
ments, the three last of which compose the organs of generation. 
