GLOW-WORMS, TERMITES, SHELLS 221 



replete with energy ; glow-worms stolid but inert ; 

 so it is with their luminary organs ; the one pulsates 

 with active flashes, the other burns with a steady 

 glow. The two luminous areas usually shine together, 

 each with the same intensity. This, however, is not 

 essential. I once watched a orlow-worm in which the 

 patch on the right side was glowing, while that on 

 the left showed not a trace of lii>ht. A faint pleam 

 soon began to appear in the non-luminous area which, 

 gradually increasing, at length equalled the brilliancy 

 of the right. Thus it would seem that the nervous 

 stimulus which controls the light may have either a 

 unilateral or bilateral action. 



Moisture has a powerful influence in exciting 

 luminosity. Glow-worms are most activ^e and usually 

 congregate in damp places. After a shower of rain 

 or when a heavy dew covers the ground their phos- 

 phorescence is more intense. I kept some glow-worms 

 away from moisture for twenty-four hours. I then 

 touched the luminous areas with a drop of water on a 

 fine brush and the luminosity increased. Even by 

 day, when the insects are inactive, the lights will 

 often shine under the stimulus of a drop of water, 

 and within a minute of comins: in contact with the 

 moisture, they often glow with the same brilliancy as 

 at night. If the insect is then placed on a piece of 

 blotting-paper to remove the moisture, the luminosity 

 will disappear. Of seven glow-worms that I kept in 

 a tin box, I noticed that only two were feebly shining 

 on a clear dry evening. I allowed some water to 

 drop gently amongst them so as to resemble the 

 falling of rain, and as each glow-worm felt a drop of 

 the fluid, it immediately became more active, began to 



