GLOW-WORMS, TERMITES, SHELLS 229 



before sunset. In this valley the termites were not 

 numerous. I saw only four flights in the one season, 

 yet all these flights took place an hour or two before 

 dark. I have never seen a flight at any other time. 

 So long as the daylight lasts the termites undergo 

 a merciless destruction ; but as the darkness increases, 

 many of them escape to found new colonies elsewhere. 

 If the complete flight of all termites was to take place 

 in the full daylight, the species would, I believe, in a 

 few years become extinct. 



Another fact which must be of some importance to 

 the survival of the swarm is that the termites in their 

 nuptial flight ascend to comparatively great heights. 

 They soon pass beyond human vision ; but, from the 

 way the swifts and kites can be seen hawking after 

 them in the air, it is clear that many must reach an 

 altitude of at least a thousand feet. This instinct 

 which impels the termites to considerable elevations 

 must be a distinct aid to the survival of the species. 

 In the first place, the insects are liable to meet with 

 high aerial currents which will waft them over long 

 distances and in this way increase their area of 

 distribution. But a Qrreater advantag-e must rest in 

 the fact that those individuals which reach a con- 

 siderable height will leave behind them a host of 

 enemies, and will therefore be the more likely to 

 survive. No doubt they meet swallows, swifts, 

 kestrels, kites, at all elevations, but they have escaped 

 the far greater multitude of insectivorous creatures 

 that would decimate them near the ground. 



Towards the termination of the flight the termites 

 seem to undergo a natural exhaustion. They descend 

 vertically from the higher elevations as though they 



