OF DIGESTION. 



103 



sometimes mounted on long, jointed stems. Insects which 

 masticate their food have, for the most part, at least two pairs 

 of horny jaws, (Figs. 60, 61, m,j,) besides several additional 

 pieces which serve for seizing and holding their food. 

 Those which live on the fluids which they extract either from 

 plants or from other animals, have the masticatory organs 

 transformed into a trunk or tube for that purpose. This 

 trunk is sometimes rolled up in a spiral manner, as in the 

 butterfly, (Fig. 64;) or it is stiff, and folded beneath the 



V 



Fig. 61. 



Fig. 62. Fig. 63. Fig. 64. 



chest, as in the squash-bugs, (Fig. 62,) containing several 

 piercers of extreme delicacy, (Fig. 63,) adapted to penetrate 

 the skin of animals or other objects whose juices they extract ; 

 or they are prolonged so as to shield the tongue when thrust 

 out in search of food, as in the bees, (Fig. 61, t.) The crabs 

 have their anterior feet transformed into a kind of jaws, and 

 several other pairs of articulated appendages performing ex- 



o' 



65. 



Fig. 66. 



clusively masticatory functions. Even in the microscopic 

 Rotifers, we find very complicated jaws, as seen in a Brachi- 

 onus, (Fig. 65,) and still more magnified in Fig. 66. But 



