INSECT VARIETY. ^7 



Many insects have the planetary power of rendei-ing- them- 

 selves visible at nig-ht, by means of a diffused light emanating 

 from various corporeal parts, and physiologists who have in- 

 vestigated the matter agree that this is generated by a soft yellow 

 secretion, intersected by tracheal ramifications, and that it is essen- 

 tially connected with the act of respiration ; but further the 

 subject is perplexed. In Kirby^s day it was a question whether 

 the light should be considered a substance, a quality of matter, 

 or the effect of vitality, and whether the chemical process in- 

 volved was a slow combustion of phosphorus or hydrogen, or an 

 emission of light which had been stored up. Although I ain 

 not aware the subject has materially progressed, or that any 

 chemist has undertaken a satisfactory analysis of the aforesaid 

 soft yellow substance, as was then suggested by Mr. S pence, 

 it is now the fashion with the scientific to compare the radiance 

 of the Glowworm either to the oxyhydrogen light, or to an 

 oxidation of carbon attendant on respiration. Phosphorescence 

 in insects does not appear confined to any order, being found 

 in beetles, moths, caterpillars, coleopterous larvae, and centipedes ; 

 and there is no reason why it should not occur in bugs, May- 

 fiies, and Mole Crickets; but the luminosity of the Lantern-flies is 

 nowadays regarded as a fiction and travellers' tale, originating 

 with Madame Meriana. As regards imagines, the luminous 

 property-hke colour secretions, though generally common, is 

 sometimes sexually marked ; the grass-frequenting female Glow- 

 worm is an often-quoted instance. " It has been supposed,^' 

 says Kirby, " that the males of the different species of Lampifrls 

 do not possess the property of giving out any light ; but it is 

 now ascertained that this supposition is inaccurate, though their 

 light is much less vivid than that of the female." 



Appended to this chapter will be found a list of insects in 

 which a luminous property has been noticed, and it has been 

 accredited to many others. In a paper just published in the 

 ''Transactions of the Entomological Society,^' the Rev. H. S. 

 Gorham has recorded his observations on the structure of the 

 Lampyridie Avith reference to their phosphorescence, directing 

 attention especially to the development of the eyes, which he finds 

 increase in size, while the pectination of the antennae is decreased, 

 in the exact ratio of the luminosity of the various species. 



