How Animals Work. 



jerky motion, the Ant-lion traces in the sand a circular 

 trench, which may vary from one to three inches in 

 diameter, and marks the edge of the snare. Having 

 completed this, the insect proceeds laboriously to dig 

 out the space thus marked to the required depth. This 

 is accomplished by moving round and round within the 

 circle, always backwards and in a descending spiral. 

 In this circular progression the action of the feet brings 

 the sand on to the surface of the flat, shovel-like head, 

 and then by a sharp jerk of the head the grains of sand 

 are thrown beyond the boundary of the pit. So active 

 is the larva that a constant shower of sand issues from 

 the pit during the process of its excavation. This toil- 

 some task accomplished, the Ant-lion lies snugly in wait 

 at the bottom of the pitfall, its ungainly body hidden 

 beneath the sand, and only the top of the head or tips 

 of the jaws showing. Nor has it generally very long 

 to wait for its prey. An inquisitive ant or small beetle 

 prying incautiously on the treacherous brink of the pit- 

 fall where there is no firm foothold, slips, and, strug- 

 gling to regain its foothold, sends down a miniature 

 avalanche of sand. Instantly the quiescent Ant-lion 

 becomes extremely active, and with its shovel-head 

 jerks up sand as fast as it can, aiming it at the unfortu- 

 nate ant and generally bringing it tumbling head over 

 heels down to the bottom of the pit. Once arrived at 

 the bottom, there is no chance of escape, for the cruel, 

 hungry jaws of the Ant-lion sink into the body of its 

 victim, which is soon sucked dry. The banquet over, 

 the Ant-lion with a jerk of the head flings the empty 

 skin of its prey out of the pitfall, and once more takes 

 up its position to await another arrival. This larval 



164 



