430 FOOD OF INSECTS. 



finishing the excavation of one circular furrow, it traces 



o 



the next in an opposite direction ; and thus alternately 

 exercises each of its legs without tiring either. 



In the course of its labours it frequently meets with 

 small stones : these it places upon its head one by one, 

 and jerks over the margin of the pit. But sometimes, 

 when near the bottom, a pebble presents itself of a size 

 so large that this process is impossible, its head not 

 being sufficiently broad and strong to bear so great a 

 weight, and the height being too considerable to admit 

 of projecting so large a body to the top. A more impa- 

 tient labourer would despair, but not so our insect. A 

 new plan is adopted. By a manoeuvre, not easily de- 

 scribed, it lifts the stone upon its back, keeps it in a 

 steady position by an alternate motion of the segments 

 which compose that part ; and carefully walking up the 

 ascent with the burthen, deposits it on the outside of the 

 margin. When, as occasionally happens, the stone is 

 round, the labour becomes most difficult and painful. 

 A spectator watching the motions of the ant-lion feels 

 an inexpressible interest in its behalf. He sees it with 

 vast exertion elevate the stone, and begin its arduous 

 retrograde ascent : at every moment the burthen totters 

 to one side or the other : the adroit porter lifts up the 

 segments of its back to balance it, and has already 

 nearly reached the top of the pit, when a stumble or a jolt 

 mocks all its efforts, and the stone tumbles headlong to 

 the bottom. Mortified, but not despairing, the ant-lion 

 returns to the charge ; again replaces the stone on its 

 back ; again ascends the side, and artfully avails himself, 

 for a road, of the channel formed bv the falling stone, 



