376 STRUCTURE OF INSECTS. 



The breast forms the second and generally the largest 

 ring of the trunk ; but sometimes it and the thorax are 

 so united, that only the depression between the two 

 can be traced ; and sometimes they are so loosely arti- 

 culated, that the breast seems part of the abdomen. 

 The upper part of the breast, which is that in which 

 the principal muscles are inserted, is covered with a 

 shield or scutellum, of a horny consistency. The ima- 

 ginary death's head and cross-bones are the bearings 

 upon this shield in the sphinx atropos. The under 

 part of this has a sternum or keel, as well as that of 

 the thorax ; to the sides of that, the two remaining 

 pairs of legs, the middle and the hind ones, are arti- 

 culated, and it sometimes covers the articulation and 

 part of the first joint of the legs, and sometimes shields 

 part of the abdomen. The wings are articulated to 

 the breast, at the sides of the scutellum, immediately 

 to the sides of it in those that have not elytra or wing- 

 covers, and in those that have, the wings and wing- 

 covers are articulated to the abdominal edge and angles 

 of the scutellum so that when the wing-covers are 

 raised, they separate from the scutellum as well as 

 from each other at the middle. 



The abdomen occupies the rest of the body. It 

 consists of a greater or smaller number of wings, ac- 

 cording to the genus of insect ; and the muscles by 

 which it is moved are inserted in the breast, the same 

 as those that move the head, and they pass diagonally 

 in the same manner. Thus the trunk, and usually 

 the breast, or second ring of the trunk, is the general 

 fulcrum of motion for the whole body. 



The wings of insects are worthy of attention, not 



