50 



GENERAL ZOOLOGY 



Fireflies are, for the most part, nocturnal in their habits, 

 clinging to the underside of leaves during the day. They 

 are protected from the insect-eating birds by a strong odor 

 which renders them distasteful. The luminous spots are 



on various abdominal 

 somites, generally the 

 last. Fireflies appear in 

 greatest numbers in the 

 latitude of the Middle 

 Atlantic states for a 

 week or more in the 

 month of June. Many 

 attempts have been 

 made to account for the 

 light produced by the 

 fireflies. The light-giv- 

 ing organ seems to con- 

 sist of fat cells inclosed 

 in a network of fine 

 tracheae. Though the 

 production of light is 

 the result of oxidation, 

 practically no heat is 

 liberated. Thus it is 

 interesting to note that 

 the efficiency of this 

 apparatus as a light- 

 producing organ is close 

 to 100 per cent. In such artificial illumination as a gas 

 jet, for example, only about 2 per cent of the radiant 

 energy consists of light rays. The function of the light of 

 the fireflies is not understood. 



The Colorado Potato Beetle. The Colorado potato beetle 

 (Leptinotar'sa decim-linea'ta) is well known to every farmer 



Fig. 34. Firefly. (Slightly enlarged) 



