14 
THE ANATOMY OF THE STAG BEETLE. 
By A. HAMMOND, F.L.S. 
[Plate H.] 
I NSECTS are Articulated Animals, in which the integument 
plays the part of the internal skeleton of Vertebrates, 
forming surfaces for the attachment and play of muscles, as 
well as a covering and protection for the vital organs they 
enclose, for which purposes it is hardened by the deposition of a 
homy substance called chitine. In their simplest form, that 
of the maggot or caterpillar, insects much resemble worms, all the 
rings of the body being nearly similar to each other. In their 
perfect condition, however, the body exhibits three well-marked 
divisions, viz. the head, the thorax, and the abdomen, the two 
former of which hear articulated appendages. An alimentary 
canal traverses the body, and presents an oesophagus, crop, 
gizzard, ventriculus, or chyle stomach, and intestine. A chain 
of double nerve- ganglia runs, united by cords, along the ventral 
surface of the body, and is connected with the cerebral ganglia, 
or brain, by cord-s surrounding the oesophagus. Opposed to 
this is an elongated contractile organ, the dorsal vessel, the chief 
agent of the circulation. Respiration is effected by means of 
tracheae, or breathing tubes, opening on the surfaces of the body 
by special apertures called spiracles.* The mouth-organs are 
modified limbs, and may be either manducatory or haustellate. 
They consist of a pair of mandibles, a pair of maxillae carrying 
palpi, and the parts forming the labium, or lower lip, viz. the 
mentum, the ligula, and a pair of labial palpi ; a horny plate 
called the labrum covers the mouth from above. Such is a rough 
outline of structures which it is intended to illustrate more fully 
in the insect which gives its title to this paper. Before, how- 
* The relative position of the alimentary, nervous, and respiratory 
systems, together with those of the different plates and appendages of the 
insect crust, are well shown in a figure from Packard. See PI. II. fig. 9. 
