172 NATURE OF INSECT LIGHTS. 



Now for a word or two, borrowed, of course, from the 

 scientific page ; but considerably at variance, respecting the 

 supposed nature and quality of this and other insect fires. 

 One experimentalist,* having found that the glowworm's 

 light is neither diminished by immersion in water, nor in- 

 creased by application of heat, that it is not capable of 

 ignition by the flame of a candle, nor possessed of any sen- 

 sible heat when separate from the bearer's body, denies in this 

 luminous matter the existence of any ordinary composition of 

 phosphorus ; suggesting, however, that the above facts are 

 favourable to the supposition of light being a quality of mat- 

 ter, rather than a substance. 



Another examiner, f on the contrary, seems to have ascer- 

 tained that the glowworm's light-diffusing substance is chiefly 

 albumen, combined with a portion of phosphorus ; and as 

 phosphorus can only become luminous by contact with oxygen 

 (supposing it uncombined with a fatty matter or albumen), he 

 considers this requisite supplied by means of the male insect's 

 respiration, which is strongest during flight ; while, in the 

 female, which flies not at all, the greater quantity of albumi- 

 nous substance contained in her thick body more than com- 

 pensates for the lesser respiratory action. 



Enough, at all events, has been ascertained about the illu- 

 minating matter of the glowworm's lamp to prove it perfectly 



* Mr. Macartney, quoted by Kirby and Spence. 

 t Mr. Macaire, quoted in ' Naturalist's Library.' 



