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CHAPTER IV. 
ON THE EXTERNAL ANATOMY OP THE COLEOPTERA. 
It will be necessary to enter somowliat fully into the 
position and names of the various parts of the external 
anatomy of Beetles, as they are constantly referred to 
in all works, either of description or classification ; and 
the common Water-beetle [Dytiscus marginalia ), before 
alluded to, will act very well as a typo, owing to its 
large size, and the well-defined outline of its compo- 
nent parts : it cannot, however, be taken as a perfect 
standard, as its paraglossas and metathoracic epimcra 
are obsolete, and its hinder coxas are enormously 
developed. The body is usually considered to be 
divided into three segments, with their respective 
appendages : viz. the head, with the eyes, antenna}, 
and mouth-apparatus; the thorax, with the elytra, 
wings, and legs ; and the abdomen, with the organs of 
generation. These segments are in reality composed 
of numerous separate parts, which we will now proceed 
to mention; there is, however, no occasion to enter 
very fully into the details of external structure, for 
which the student can refer to several of the larger 
works ; but the principal parts of the body, with the 
names by which they are now usually known, must be 
enumerated, — it being absolutely necessary to under- 
stand them in working from descriptions. 
