14 MODERN CLASSIFICATION OF INSECTS. 



preceding with the femur, which, in general, is the thickest part of the 

 legs, and generally extends beyond the sides of the body. In leaping 

 insects it is especially incrassated and often toothed beneath. The next 

 piece is the tibia, which is generally nearly equal in length, but more 

 slender than the femur ; it is an important piece of the leg, and is often 

 armed with various appendages, especially at its tip, where they 

 generally assume the appearance of spurs, or acute points (calcaria). 

 The tarsus is a jointed piece, armed at its extremity with one or two 

 slender curved hooks (ungates), and often accompanied by membran- 

 ous or fleshy cushions {jmlvilU). The number of joints in the tarsi 

 varies from two to five. This part of the leg affords important 

 characters for generical and family distinctions. 



The Abdomen consists of a series of segments, for the most part 

 destitute of any appendages, which last are to be found only in a few 

 species, where they appear either as the external organs of genera- 

 tion, or as filaments, or other analogous pieces attached to the ex- 

 tremity of the body. These segments are attached together by 

 membranes, and either meet at the edges or slide into each other like 

 the tubes of a telescope ; each of them is formed of two arcs, or 

 semi-segments, one of which is dorsal, and the other ventral. The 

 typical number of segments is rarely to be found in the perfect state, 

 some of them being ordinarilj^ employed in the construction of the 

 organs of generation ; in the male Earwig, however, nine distinct ab- 

 dominal segments, exclusive of the anal forceps, are to be observed. 

 The abdomen is attached to the posterior thoracic segment, either 

 by its whole breadth, when it is said to be sessile, or by a slender 

 portion of its base, which is called a peduncle : this latter mode of 

 articulation is especially to be observed in the majority of the Hymeno- 

 ptera, and some other orders. The chief appendages of the abdomen 

 are the ovipositor, which is extremely varied in the different tribes, 

 (being sometimes replaced by a powerful sting,) and the elongated 

 setae, forceps, or other analogous organs. 



With respect to the Internal Anatomy of insects, a ^e\v brief notes 

 must here suffice. They arrange themselves under the head of the 

 sensitive, digestive, circulatory, respiratory, muscular, and generative 

 systems. 



The Senses of insects are dependent upon the action of the nerves, 

 the system whereof in insects consists of a pair of medullary threads, 

 exhibiting a series of knots or ganglia, whereby they are united 



