119 



CHAP. X. 



LIGHT EMITTED FROM VEGETATION. EXOTIC LU- 

 MINOUS INSECTS, PAUSUS SPH^EROCEROS, AND 



OTHERS. ELATER NOCTILUCUS. FULGORA LAN- 



TERNARIA AND CANDELARIA. INDIAN GROSBEAK. 



LAMPYRIS NOCTILUCA, OR GLOW-WORM, HABITS, 



ETC. LAMPYRIS ITALICA. 



LIGHT is derived from a variety of sources, but the 

 present enquiry embraces the question as connected 

 with the living system, chiefly the insect world, in some 

 of which it forms a very wonderful investiture. De- 

 cayed wood and some plants emit a phosphorescent 

 light ; and the potato, when in a heap, is said to be 

 sometimes luminous. Some of these species of illumin- 

 ation are of an electric kind ; others are owing to the 

 occasional presence of luminous. insects, as the scolo- 

 pendra electrica, &c. ; and sometimes, we have no doubt, 

 to the presence of luminous ova, or parasitic luminous 

 animalculae : the increase of temperature on the decom- 

 position of vegetable matter might be a sufficient cause 

 of evolution. Plants of the rhizomorpha kind are dis- 

 covered often luminous in mines. Mr. James Ryan 

 informs us he has met with plants in mines almost 

 sufficiently luminous to read by ; and the counsellor 

 Erdmann thus describes the luminosity of the rhizo- 

 morpha, in one of the coal mines near Dresden : 

 " I saw the luminous plants here in wonderful beauty ; 

 the impression produced by the spectacle I shall never 

 forget. It appeared on descending into the mine as 

 if we were entering an enchanted castle, the abun- 



