ABDOMEN. 289 



some lepidopterous insects, especially amongst the butterflies 

 belonging to the family Nymphalidce, the fore-legs are very 

 short and rudimental, the tarsi being almost obliterated, and 

 quite unfitted for walking. In some insects the various parts 

 of the leg fold upon each other when unemployed, and are 

 then received- into certain channels prepared for their recep- 

 tion on the under side of the thorax. This is the case with the 

 pill-beetles (Byrrhidce), mimic-beetles (Histeridte), &c. As 

 regards the relative proportions of the legs of insects, the 

 general rule is, that the anterior are the shortest, and the 

 posterior the longest; and as regards their length, the short- 

 er and more robust the body, the shorter are the legs, and 

 vice versa. In running insects, also, the legs are longer than 

 in those which crawl. Generally, the legs do not much ex- 

 ceed the body in length, but occasionally they are much 

 longer. As regards their direction, the anterior legs are 

 generally directed forwards, and the four posterior back- 

 wards. It would, however, occupy far too much space were 

 we to enter into a detailed notice of all the variations in form 

 which occur in the legs of insects. 



C. The Abdomen, or the Seat of the Organs of Generation. 

 We have now arrived at the third and last principal division 

 of the body, which incloses the greater portion of the intes- 

 tines, the organs of generation, and their appendages. Un- 

 like the preceding part of the body, the abdomen, from being 

 destitute of locomotive organs, necessarily exhibits a much 

 less complicated organization in the various segments of 

 which it is composed than those of the thorax, and typically 

 consists of nine segments, exclusive of the anal apparatus, 

 each being composed of two arcs, or half segments, one 

 upper and the other under. These rings are attached together 

 by membrane, and either meet at the edges, or slide into each 

 other like the tubes of a telescope. The dorsal ones are termed 



