342 NATURE OF INSECT LIGHTS. 



drew them under the shielding back-plate which covered the 

 fore-part of her body ; that slate-coloured, oblong, flat, wingless 

 body, all divided into rings, and bearing at its nether extremity 

 the lamp, by night a lustrous emerald, by day a dull pale 

 spot, composed, as we have learnt now, of the sulphur-coloured 

 substance which supplies its light. 1 



Of this article, by the way, though it cost her nothing, the 

 glowworm, it would seem, is somewhat economic; Gilbert White, 

 at least, confirmatory of Will Shakespeare, having thought 

 that she always puts out her light at the decent hour of eleven 

 or twelve, or begins then, according to the poet and the poetic 

 idea, to " pale her ineffectual fire." 



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, 2 having found that the glowworm's light 

 is neither diminished by immersion in water, nor increased by 

 application of heat, that it is not capable of ignition by the 

 flame of a candle, nor possessed of any sensible 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 matter, rather than a 

 substance. 



Another examiner, 3 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 albuminous 



1 See Vignette. 2 Mr. Macartney, quoted by Kirby and Spence. 



3 Mr. Macaire, quoted in " Naturalist's Library." 



