286 THE ENTOMOLOGIST. 



spots on each side of the surface of llie thorax. This is 

 sometimes observed even while the insects are flying about, 

 if the position of the spectator is such that the under side of 

 the body is exposed to him. Then he sees a light much 

 more brilliant than usual, appearing and disappearing with 

 the motion and change of position of the insect. 



1 may here observe that the diffusion of the light through- 

 out the whole body, as in this new larva, is a phenomenon 

 more easy of comprehension than is its limitation to the ter- 

 minal segments of the abdomen as in the glowworm, or to 

 the nasal projection as in the Fulgora (always supposing the 

 reported luminosity of that organ in them to be really true). 

 It appears to me that the phenomenon in all these insects is 

 one of chemical action, and that the chemical action is that 

 of oxidization produced by respiration — in other words, 

 combustion. This is supported by the fact that, if we place 

 a glowworm in oxygen, the light becomes greatly more bril- 

 liant, the process of oxidizatian 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 energetic to produce phospho- 

 rescence without actual ffame ; and I am very much disposed 

 to believe that the 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 atmo- 

 sphere unusually charged with oxygen, and seen by persons 

 possessed of unusual acuteness of vision or nervous sensi- 

 iDility. 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 



