UGHT-GIVINQ C0LE0PTEE0U3 LARVA. 79 



tiou — in other words, combustion. This is supported by the fact 

 that, if we place a Glowworm in oxygen, the light becomes 

 greatly more brilliant, the process of oxidization by respiration 

 being assisted by the greater amount of oxygen surrounding 

 the animal. It is, the same operation as the combustion of 

 the carbon in our own bodies when exposed to the action of 

 oxygen in the lungs; only in the insect the lungs, instead 

 of being confined to the thorax, are replaced by a series of 

 tracheae which ramify through the body. In our own bodies 

 and in those of most other, animals the combustion in question is 

 carried on too feebly and in too diluted a state to produce light ; 

 but it is easy to conceive that a more active operation of oxidi- 

 zation might be sufficiently energetie to produce phosphorescence 

 without actual flame ; and I am very much disposed to believe 

 that tlie stories of odylic light averred to have been seen by 

 highly sensitive mesmerisers streaming from the bodies of others, 

 are only instances of such exceptionally active oxidization, going 

 on perhaps in a state of the atmosphere unusually charged with 

 oxygen, and seen by persons possessed of unusual acuteness of 

 vision or nervous sensibility. But although this theory may to 

 a certain extent explain the phenomenon of luminousness in those 

 animals or plants where it is observable in every part subjected 

 to the influence of oxidization, it is more difficult of application 

 in those cases where the light is confined to some special part 

 or organ, as in the Glowworm. In it the light is confined 

 to a special organ, which is supplied with special nerves which 

 control the display of light at the will of the animal. Still I 

 hold that that light when put in action is the result of slow 

 combustion. 



There is obviously much room for interesting experiment and 

 observation regarding the luminosity of insects. I have alluded 

 to the greater splendour of the light when the Glowworm is 

 placed in oxygen. Might not the combustive action be so in- 

 creased by continued replenishment and saturation or conden- 

 sation of oxygen as actually to ignite the animal by its own 

 respiration ? Might not luminosity be detected under similar 

 circumstances in other insects which are not usually luminous, 

 or in some parts of them ? 



It is possible, too, that there may be more than one me.ins 

 by which the phenomenon of luminosity is produced. We too 

 often mislead ouraclvcs by referring similar cflects to one cause. 



