GLOW-WORMS, TERMITES, SHELLS 235 



twenty times its own weight. It works very inter- 

 mittently, a long pause being made after a few violent 

 exertions. This must be a necessary division of rest 

 and labour in a creature that employs such sudden 

 and impetuous efforts. Should a stone, which is 

 beyond the strength of the larva to remove, tumble 

 into the pit, it burrows a little to one side until clear 

 of the obstruction, then commences to hurl up sand, 

 and thus constructs a fresh dwelling-place by shifting 

 laterally the bottom of the pit. 



On a still day the ant-lion patiently waits in the 

 floor of its funnel till the unwary ant tumbles in. But 

 in windy weather the larva leads a more strenuous 

 life. The force of the wind continually levels the 

 surface of the sand ; every depression in the ground 

 is to some degree lessened and the pit of the ant-lion 

 tends to be filled in. Grains of sand pour down the 

 sides of the pit ; it would soon be flush with the 

 surface did not the ant-lion make every effort to 

 contest the downpour. It hurls out the sand as fast 

 as it rolls in ; in circles it revolves round and round 

 the bottom of its cone, pitching out the sand that 

 would engulf it. Every day of wind is for this larva 

 a day of continuous toil. 



Though ant-lions are almost always seen waiting 

 in the bottom of their pits, yet they sometimes wander 

 about on the surface of the sand. A number seem 

 to move about at the same time, leaving in their tracks 

 lines of sinuous furrows as though a crowd of tiny 

 snakes had been creeping through the dust. 



I will now mention a few observations on the fresh- 

 water shells of the valley. The dispersal of shells is a 

 subject which has excited the interest of our greatest 



