44 GENERAL ZOOLOGY 



tracheae. The process is, therefore, a form of oxidation. It 

 is interesting to note that the efficiency of this apparatus as 

 a light-producing organ has been estimated at 100 per cent. 

 In such artificial illumination as a gas-jet, for example, only 

 about two per cent of the radiant energy consists of light-rays. 

 The function of the light of the fireflies is not understood. 



Scarabs. Certain beetles of a quite different group have 

 long attracted the attention of observers by their curious 

 habit of forming and rolling about a pellet of manure for food 

 for themselves or their larvae. We have several species of 

 these beetles in the L T nited States, but the best known of the 



FIG. 27. Sacred Beetle and Scarab in Stone, x 2 



group is the sacred beetle of the Egyptians (Ateu'chus sa'cer, 

 Fig. 27), the Scarabceus of the ancients, figures of which are 

 found carved in stone on the monuments of ancient Egypt. 

 These beetles played an important part in the symbolism of 

 the Egyptians, to whom they typified the world and the sun, 

 - the former on account of their round pellets, the latter 

 on account of the projections on the head, which were likened 

 to the rays of the sun. 



To the same group belong our common May -beetles or June- 

 beetles (Lachnoster'na, Fig. 28). These beetles live in the 

 ground in the larval stage, feeding on the roots of plants. 



