THE ANATOMY OF THE STAG BEETLE. 
21 
and lias been already noticed. The prsescutum lies in front of 
the wings, and the post- sent ellum, as its name indicates, follows 
the scut ellum. The two last-named subdivisions are generally 
bent downwards, to form attachments for the great longitudinal 
muscles of flight. In the lateral plates, just below the inser- 
tion of the wings, we again distinguish the episternum and 
epimeron ; but so altered are the relative position of these pieces 
by the great development of the sternum, that we can scarcely 
recognize them as anterior and posterior in their relative posi- 
tion, but rather as inferior and superior. They will be seen 
represented in PI. II. fig. 10. The sternum, or ventral plate of 
this segment, is the largest piece in the insect, and is divided 
by a central suture (see Pl. II. figs. 2 and 10). Although its 
typical position is between the legs, and indeed actually is so 
in some insects, it will generally be found in front of, rather than 
between, the coxae, as in the present instance ; it is of great 
strength, and gives origin to the great volume of muscles which 
occupy the lateral portions of the segment. Together with the 
greatly developed posterior coxae which lie behind it, it extends 
the ventral surface of the metathorax far beyond its dorsal 
limits, which are marked by the inwardly developed post- 
scutellum; and the consequence is noteworthy. The ventral 
plate of the succeeding or fifth segment of the insect has dis- 
appeared, only the dorsal plate remains (Pl. II. fig. 8) to occupy 
the vacancy caused by the deficient backward extension of the 
dorsal surface.* This plate in the Stag Beetle assumes the 
appearance of, and is continuous with, the succeeding dorsal 
plates of the abdomen ; but except at its posterior margin, it is 
connected on all sides with the metathorax ; so that from one 
point of view we may regard it as the commencement of the 
abdomen, and from another as the termination of the thorax ; 
thus illustrating the lack of that sharp separation between 
thorax and abdomen, in other words, the deficiency of regional 
distinction as compared with the Metabola which has been 
already referred to, while the great differentiation in form, 
in size, and in function, between the two wing-bearing 
segments, ranks the Coleoptera at once above the other orders 
of the Heterometabola with which it is associated. 
The abdomen is that portion of the body of the insect which 
most strikingly retains its original articulate form, fulfilling, as 
it does, the functions of nutrition and reproduction which are 
characteristic alike of the lowest as well of the highest types of 
the Articulata. Perhaps it will be better to regard with New- 
port the fifth segment just described as a piece by itself, the 
thoracico-abdominal segment ; then the true segments of the 
* This plate, as stated on p. 19, is in the Hymenoptera included with 
the thorax in front of the thoracico-abdominal incisure. 
