LUMINOUS INSECTS. 4.25 
With respect to the remote cause of the luminous 
property of insects, philosophers are considerably di- 
vided in opinion. The disciples of modern Chemistry 
have in general, with Dr. Darwin, referred it to the 
slow combustion of some combination of phosphorus 
secreted from their fluids by an appropriate organiza- 
tion, and entering into combination with the oxygene 
supplied in respiration. This opinion is very plausibly 
built upon the ascertained existence of phosphoric acid 
as an animal secretion; the great resemblance between 
the light of phosphorus in slow combustion and animal 
light; the remarkably large spiracula in glow-worms; 
and upon the statement, that the light of the glow-worm 
is rendered more brilliant by the application of heat and 
oxygene gas, and is extinguished by cold and by hydro- 
gene and carbonic acid gases. From these last facts 
Spallanzani was led to regard the luminous matter as a 
compound of hydrogene and carburetted hydrogene gas. 
Carradori having found that the luminous portion of the 
belly of the Italian glow-worm (Lampyris italica) shone 
in yacuo, in oil, in water, and when under other cir- 
cumstances where the presence of oxygene gas was pre- 
cluded, with Brugnatelli ascribed the property in ques- 
tion to the imbibition of light separated from the food or 
air taken into the body, and afterwards secreted in asen- 
sible form?. Lastly, Mr. Macartney having ascertained 
by experiment that the light of a glow-worm is not di- 
minished by immersion in water, or increased by the ap- 
point is not very clear. He probably means that the insect will not 
shine in a dark place in the day time, unless previously exposed to 
the solar light: for it is often seen to shine at night when it could 
have had no recent exposure to the sun. a 
@ Annal. di Chimica, xiii. 1797. Phil. Mag. u. 80. 
