MUSCULAR SYSTEM. 139 



FIG. 64. 



breadth and form from their origin to their insertion ; but in 

 the anterior part of the trunk, where the movements are 

 more powerful, the muscles have generally a conical form, 

 being broad at their origin, and tapering towards their point 

 of insertion ; so that more muscles can be inserted into a 

 limited point, to strengthen and vary its movements. This 

 form is seen in the depressor muscle (a,) of the head, and in 

 the lateral flexor (6,) of the same part. The fasciculi of the 

 rotator (d } ) of the head are more parallel, but they converge 

 to a point in the two portions of the levator capitis (e, y,) 

 and in the inferior (c,) and the superior (f,) retractor of the 

 corselet, the levator (a?,) of the corselet, and the levator 

 obliquus (h,) of the jugular piece. The fasciculi are more 

 parallel in the large and powerful depressor muscle (i,) of the 

 wing, on which the flight of the insect so much depends, 

 and also in the several portions of its broad levator muscles 

 (k.) The same tapering and pointed form is seen in most 

 of the muscles in the region of the pelvis, or attached to 

 the moveable pieces of the anus, as in the strong levator (n,) 

 of the inferior anal piece, the retractor preputii (y,) the 

 posterior retractor (/?,) of the inferior anal piece, and the 

 retractor of the cloaca (o.) There is also great uniformity 

 observed in the disposition of the flexor and extensor 

 muscles in the ginglimoid articulations of the legs in all the 

 entomoid classes, and in the more moveable rotating articu- 

 lations of the antennee and palpi of these animals. The 

 muscles of the trunk in these highest articulated classes, 

 like those of the helminthoid forms, are still divided into 

 bands, which occupy chiefly the dorsal and the ventral 

 aspects of the body, and these are again partially divided 



