FIRE-FLIES. 61 



black or rusty-brown color ; and, if observed during the day- 

 light, two conspicuous oval spots of a yellowish white Ime 

 are seen on each side of the prothorax. These are the lan- 

 terns of the Elaters, and in the dark glow with a brilliancy 

 far exceeding that of the liglitning-bugs. These lights shine 

 from above, while between the part known as the metathorax 

 and the first abdominal segment gleams another, or lower 

 light, even more brilliant than the other : so the Pyrophorus, 

 turn which way it will in its flight, emits a flash of light. 

 The light appears to be dependent upon the will, as when 

 feeding or asleep it is not seen ; attaining its greatest bril- 

 liancy during activity and flight. The color of the light, as 

 seen by the author, is a rich green ; but the eggs emit a light 

 of a bluish tint, according to Dubois. This naturalist has 

 made some extremely interesting experiments with this 

 beetle. The eggs which he dried retained their luminosity 

 for a week, the light re-appearing when they were placed in 

 water. He ground the luminous organs in a mortar, after 

 having dried them in vacuum, and then mixed them in boiled 

 water ; the latter immediately becoming luminous. Dr. Du- 

 bois concludes that the light of the Pyrophorus is intended 

 as an illuminator for itself alone. To prove this, he covered 

 one of the upper lights with wax, and the animal moved in 

 a curve ; when both spots were covered, the beetle soon 

 stopped, and then moved in an uncertain manner, earefully 

 feeling the ground with its antennce. The spectrum of the 

 light was extremely beautiful, being continuous, without dark 

 or brilliant rays ; and, what appears most remarkable, the com- 

 position of the light was found to change with its intensity. 

 As to the exact cause of the light, how it is produced, the 

 secret yet rests with Nature. 



