INSECTS 



With the conditions of living granted, however, proto- 

 plasm is still only potentially alive, for there is yet required 

 a stimulus to set it into activity. The stimulus for life 

 activities comes from changes in the physical forms of 

 energy that surround or infringe upon the potentially 

 living substance; for, "live" matter, like all other matter, 

 is subject to the law of inertia, which decrees that it must 

 remain at rest until motion is imparted to it by other 



Md— ■ 



Fig. 66. The head and mouth parts of a grasshopper 



A, facial view of the head, showing the positions of the antennae {Ant), the 

 large compound eyes (E), the simple eyes, or ocelli (O), the broad front lip, 

 or labrum {Lm) suspended from the cranium by the clypeus {Clp), and the 



bases of the mandibles {Md, Md) closed behind the labrum 



B, the mouth parts separated from the head in relative positions, seen from 

 in front: Hphy, hypopharynx, or tongue, attached to base of labium; Lb, labium; 



Lm, labrum; Md, mandibles; Mx, maxillae 



motion. A very small degree of stimulating energy, how- 

 ever, may result in the release of a great quantity of 

 stored energy. 



The food of all living matter must contain carbon, 

 hydrogen, nitrogen, and oxygen. The mechanism of 

 plants enables them to take these elements from com- 

 pounds dissolved in the water of the soil. Animals must 

 get them from other living things, or from the products of 



f 106I 



