Muscles 



^0 



_ Add. of coia 



others which are attached to the forks, bring about 



motion between the various segments of the thorax. 



The muscles which move the wings are attached to 



the lower region of the thoracic wall, and pass thence 



upwards, those {elevators) 



which by their contraction 



raise the wing being fixed 



to the wing-root at a point 



inside the fulcrum of its 



attachment to the body, 



while those (depressors) 



whose contraction lowers 



the wing are attached to 



the wing-root outside the 



fulcrum. 



From the prothorax, 

 slender muscles for moving 

 the head pass forward and 

 are attached to the head- 

 capsule, within which are 

 found sets of muscles act- 

 ing on the feelers and 

 jaws (l). The muscles of 

 the heart and food-canal 

 will be considered in 

 connection with those 

 organs. 



The arrangement of 

 muscles thus briefly de- 

 scribed, as found in the 

 cockroach, becomes modi- 

 fied in many respects in 

 other insects. For instance, 

 in most Flics, Ants, Bees and their allies there is much 

 less motion between the segments of the hind-body than 

 in the cockroach, while between the segments of the 



Retr. Ura. 



Fig. :^8. — Muscles of Cockroach's left 

 leg of middle pair. Magnified. 

 After Miall & Denny. 



