The Glow- Worm and Other Beetles 



is drawn over the flame at will, or is that 

 flame always left exposed? There is no 

 need for any such mechanism: the insect has 

 something better for its revolving light. 



The thick tube supplying the light-pro- 

 ducing sheet increases the flow of air and 

 the light is intensified; the same air-tube, 

 swayed by the animal's will, slackens or even 

 suspends the passage of air and the light 

 grows fainter or even goes out. It is, in 

 short, the mechanism of a lamp which is 

 regulated by the access of air to the wick. 



Excitement can set the attendant air-duct 

 in motion. We must here distinguish be- 

 tween two cases: that of the gorgeous 

 scarves, the exclusive ornament of the female 

 ripe for matrimony, and that of the modest 

 fairy-lamp on the last segment, which both 

 sexes kindle at any age. In the second case, 

 the extinction caused by a flurry is sudden 

 and complete, or nearly so. In my noc- 

 turnal hunts for young Glow-worms, measur- 

 ing about 5 millimetres long, 1 I can plainly 

 see the glimmer on the blades of grass ; but, 

 should the least false step disturb a neigh- 

 bouring twig, the light goes out at once and 

 the coveted insect becomes invisible. Upon 

 the full-grown females, lit up with their 



1 .195 inch. — Translator's Note. 

 20 



