INSECT STRUCTURES 15 



protection and overcoming other insects which serve as 

 food for the larvae. 



16. The Muscular System. Insects have a wonder- 

 fully developed system of muscles. As many as two 

 thousand separate muscles have been identified in certain 

 larvse. The muscle tissue is soft and watery in appear- 

 ance in the living insect and is made up of striated fibers 

 ending in tendon-like cords which are attached to the dif- 

 ferent organs and to the hardened processes projecting in- 

 ward from the skeleton for this purpose. The strength 

 of these muscles seems to be much greater in proportion 

 to their size than is the case in other animals and many 

 wonderful tales are told of the muscular power of insects. 

 Some of these may easily be verified by original observa- 

 tion. 



17. The Fat-Body. Much of the space in the body 

 cavity of some forms of insects is taken up by the fat- 

 body. This is tissue similar to the fatty tissue of the ver- 

 tebrates and serves much the same purposes, namely, 

 storage of food and, to a degree, support for the more del- 

 icate organs. The fat-body consists of cells of rather large 

 size, arranged in masses which are usually distinct in the 

 different segments. 



18. Special Organs and Adaptations. There are spe- 

 cializations, external and internal, of the most varied na- 

 ture, which are usually directly connected with the func- 

 tions of one or other of the above-mentioned systems of 

 organs. Among these there are few that are more striking 

 than those of the respiratory apparatus. These are fre- 

 quently adaptations for an aquatic habitat. The most 

 simple of the arrangements by means of which an insect 

 is enabled to obtain air while beneath the surface is that 

 by means of which the insect can carry a bubble of air 



