LETTER XXV. 



ON LUMINOUS INSECTS. 



We boast of our candles, our wax-lights, and our Ar- 

 gand-lamps, and pity our fellow-men who, ignorant of 

 our methods of producing artificial light, are con- 

 demned to pass their nights in darkness. We regard 

 these inventions as the results of a great exertion' of 

 human intellect, and never conceive it possible that 

 other animals are able to avail themselves of modes of 

 illumination equally efficient ; and are furnished with 

 the means of guiding their nocturnal evolutions by ac- 

 tual lights, similar in their effect to those which we 

 make use of Yet many insects are thus provided. 

 Some are forced to content themselves with a single 

 candle, not more vivid than the rush-light which glim- 

 mers in the peasant's cottage ; others exhibit two or 

 four, which cast a stronger radiance ; and a few can 

 display a lamp little inferior in brilliancy to some of 

 ours. Not that these insects are actually possessed of 

 candles and lamps. You are aware that I am speak- 

 ing figuratively. But Providence has supplied them 

 with an effectual substitute — a luminous preparation 

 or secretion, which has all the advantages of our lamps 

 and candles without their inconveniences ; which gives 

 light sufficient to direct their motions, while it is inca- 

 pable of burning j and whose lustre is maintained with- 



