6 MODERN CLASSIFICATION OF INSECTS. 



the primary segments is typically composed of four other segments; 

 but as it is only in the thorax that this complex structure is to be 

 traced, I shall notice it in describing that part of the body. 



The Distribution of the Seffments of the body of insects into three 

 distinct regions (head, thorax, and abdomen), although not observable 

 in the early states of existence of many species (ex. gr, larva) of 

 Lepidoptera), wherein the body is composed of a series of nearly 

 equal-sized continuous rings, is so essentially indicated in the last and 

 highest state of perfection of the animal, that we may, with propriety, 

 adopt the Linnsean division of the body, into head, thorax [truncus'L.^ , 

 and abdomen ; but the limbs (artus), being attached to the segments 

 forming the thorax, are to be regarded as appendages thereto, and 

 not as distinct primary parts of the body, in the same manner as the 

 antenna; and trophi are appendages of the head ; and the ovipositor, 

 sting, caudal forceps, &c., appendages of the abdomen. These three 

 primary divisions of the body appear to be adapted for distinct ob- 

 jects of equally great importance in the physiological relations of the 

 animal. The head comprises the organs of sense, and consists of a 

 single segment. The thorax comprises the organs of locomotion, and 

 is composed of the three following segments ; and the abdomen, which 

 contains the generative organs, comprises the remaining segments. 



The Head is a generally corneous, and often somewhat globose, 

 skull; having an opening in its anterior part for the reception of the 

 organs of the mouth (troplii), and a similar opening at its posterior 

 part, where it is attached to the following segment, and through 

 which the cesophagus or other anterior part of the digestive canal 

 passes. On each side of the head Is fixed an immoveable eye, of 

 large size and complex structure, between which are occasionally 

 two, or oftener three, minute simple lenses (ocelli). Towards the 

 front of the head, but behind the mouth, are also attached two move- 

 able organs, of endless variety of form, size, and structure, which are 

 , termed antenna;, and of which the precise uses have not been deter- 

 mined. The front margin of the head is often separated by a suture 

 from the remainder of the skull, and is then termed the Clypeus. 

 The under surface of the head is the Jugulum K. (Gula, Strauss, and 

 Burm.), the swollen anterior margin of which is the "piece prcbasilaire" 

 of Strauss and Burmelster (Manual, pi. Hi. f. 12. d, d), being the stipes 

 of MacLeay, and the mentum and insertion of Newman. It is to 

 the front margin of this swollen part that the true mentum is attached. 



