LECT. VIII. GLOW-WORM. 155 



Glow-worm. I shall engage your attention for some 

 time on the phosphorescence of a well-known insect, by 

 giving you an account of the most conclusive experiments 

 made some time since by Macaire and other natural philoso- 

 phers, and recently by myself. The insect I speak of, is 

 the Lampyris Italica* or Italian glow-worm, commonly 

 called ver luisant in France, and lucdola in Italy. It is a 

 coleopterous insect living in the grass, and which shows it- 

 self after sunset in spring and summer. The two last seg- 

 ments of its body, which by day appear yellowish, are slightly 

 luminous in the dusk, and during the night evolve a bright 

 intermittent light. 



The light sometimes ceases suddenly, either when the 

 insects are gently touched, or at times when they have not 

 been touched, and subsequently re-appears again. 



This fact led Macaire to suppose, that the phosphores- 

 cence was under the will of the animal. The cessation of 

 the luminosity is certainly not effected by an opaque mem- 

 brane, which it was supposed the insect drew over its rings, 

 for no such membrane exists. 



We shall find, in the course of this lecture, that every- 

 thing leads us to assume that the phosphorescence is not 

 continuous, because the cause that produces it is not persis- 

 tent ; and that we can explain the intermittence of the phe- 

 nomenon. 



In studying this subject, the observation which has always 

 excited my astonishment is, that the yellowish matter con- 

 tained in the terminal rings of the insect continues to emit 

 light when separated from the body of the animal. If we 

 kill one of the insects and crush it between the fingers, 

 long streaks of light are perceived to issue from the yellow- 



* The insect above noticed, under the name of Lampyris Italica, is by 

 some authors referred to another genus. In Dejean's Catalogue it is 

 called, Colophotia Italica. J. P. 



