THE GLOW-WORM 45 



III 

 His LAMP 



If the Glow-worm possessed no other talent than that of 

 chloroforming his prey by means of a few tweaks as gentle 

 as kisses, he would be unknown to the world in general. But 

 he also knows how to light himself like a lantern. He shines ; 

 which is an excellent manner of becoming famous. 



In the case of the female Glow-worm the lighting-apparatus 

 occupies the last three divisions of the body. On each of 

 the first two it takes the form, on the under surface, of a wide 

 belt of light ; on the third division or segment the bright part 

 is much smaller, and consists only of two spots, which shine 

 through the back, and are visible both above and below the 

 animal. From these belts and spots there comes a glorious 

 white light, delicately tinged with blue. 



The male Glow-worm carries only the smaller of these 

 lamps, the two spots on the end segment, which are possessed 

 by the entire tribe. These luminous spots appear upon the 

 young grub, and continue throughout life unchanged. And 

 they are always visible both on the upper and lower surface, 

 whereas the two large belts peculiar to the female shine only 

 below the body. 



I have examined the shining belt under the microscope. 

 On the skin a sort of whitewash is spread, formed of some 

 very fine grain-like substance, which is the source of the light. 

 Close beside it is a curious air- tube, with a short wide stem 

 leading to a kind of bushy tuft of delicate branches. These 

 branches spread over the sheet of shining matter, and some- 

 times dip into it. 



It is plain to me that the brightness is produced by the 

 breathing-organs of the Glow-worm. There are certain sub- 

 stances which, when mixed with air, become luminous or even 

 burst into flame. Such substances are called combustible, and 

 the act of their producing light or flame by mingling with the 



