IN CONSTRUCTING BRIDGES, 247 
glass (A) containing the larve 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) 3, of an inch above the glass 
(4), exactly the same result occurred. The ants bent 
over and made every effort to reach the larve, but did 
not drop themselves down, and after a while again 
abandoned all hope of getting the larve. 
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 
larve in a cup which I put on a slip of glass surrounded 
by water, but accessible to the ants by one pathway in 
which was a bridge consisting of a strip of paper % 
inch long and 3 inch wide. Having then put a Lasius 
niger from one of my nests to these larve, 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 4. 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 
