122 Facts, Observations, and Experiments, relative 



If a longitudinal incision be made through both scuta, 

 the whole becomes luminous, and the insect cannot pre- 

 vent it. 



Now, from all this it would seem, that the air taken in, 

 by the spiracula, for the support of life, has no commu- 

 nication with that which causes, or contributes to, the 

 elimination of light. Certain it is (as relates to our Ame- 

 rican lampyris at least), that oxygen is essentially neces- 

 sary to this effect. But whether this vital support be 

 taken in through those spots which appear like perfora- 

 tions (or, perhaps, are such), or acts in some other way, I 

 know not ; but I should rather incline to think, that the 

 spots, alluded to, are not perforations, and, therefore, 

 that the air must come in contact with the phosphores- 

 cent substance in some other way. 



Viewing a live insect, laid on its back, through a pow- 

 erful double microscope, in a very dark room, or at 

 night, its own light enabled me to see it tolerably dis- 

 tinct : for, in that situation, it is considerably luminous, 

 during the intervals between the flashes. When it gave 

 light by volition, the suddenness of the flash made so great 

 a contrast to the ordinary appearance, that the eye could 

 not accommodate itself so as to discern any thing, ex- 

 cept that the luminous portion did not appear to be at all 

 altered in its dimensions, no motion whatever being per- 

 ceptible. And this is another reason which leads me to 

 suppose, that the air is not taken in by the means above 

 hinted at. 



