m CONSTHUCTING BRIDGES. 247 



glass (a) containing the larvae so as to touch the piece 

 of wood (d), and again put some ants to the larvae. 

 Soon a regular string of ants was established ; when I 

 again raised the wood (d) -j^ of an inch above the glass 

 (a), exactly the same result occurred. The ants bent 

 over and made every effort to reach the larvae, but did 

 not drop themselves down, and after a while again 

 abandoned all hope of getting the larvae. 



In order to test their intelligence, it has always 

 seemed to me that there was no better way than to 

 ascertain some object which they would clearly desire, 

 and then to interpose some obstacle which a little 

 ingenuity would enable them to overcome. Following 

 up, then, the preceding observations, I placed some 

 larvae in a cup which I put on a slip of glass surroimded 

 by water, but accessible to the ants by one pathway in 

 which was a bridge consisting of a strip of paper f 

 inch long and ^ inch wide. Having then put a Lasi/us 

 niger from one of my nests to these larvae, she began 

 carrying them off, and by degrees a number of friends 

 came to help her. I then, when about twenty-five ants 

 were so engaged, moved the little paper bridge slightly, 

 so as to leave a chasm, just so wide that the ants could 

 not reach across. They came and tried hard to do so ; 

 but it did not occur to them to push the paper bridge, 

 though the distance was only about ^ inch, and they 

 might easily have done so. After trying for about a 

 quarter of an hour, they gave up the attempt and re- 

 turned home. This I repeated several times 



