Ants. 6 r 



which, however, was just out of their reach, though 

 they could touch it with their antennae ; but it did 

 not occur to them to heap the earth up a little, 

 though if they had moved only half a dozen par- 

 ticles of earth they would have secured for them- 

 selves direct access to the food. At length they 

 gave up all attempts to reach up to the glass, and 

 went round by the paper bridge. I left the arrange- 

 ment for several weeks, but they continued to go 

 round by the long paper bridge. 



5. Again I varied the experiment as follows: 

 Having left a nest without food for a short time, I 

 placed some honey on a small wooden brick sur- 

 rounded by a little moat of glycerine half an inch 

 wide and about one-tenth of an inch in depth. 

 Over this moat I then placed a paper bridge, one 

 end of which rested on some fine mould. I then 

 put an ant to the honey, and soon a little crowd 

 was collected round it. I then removed the paper 

 bridge : the ants could not cross the glycerine ; 

 they came to the edge and walked round and 

 round, but were unable to get across, nor did it 

 occur to them to make a bridge or bank across the 

 glycerine with the mould which I had placed so 

 conveniently for them. I was the more surprised 

 at this on account of the ingenuity \vith which they 

 avail themselves of earth for constructing their 

 nests. For instance, wishing, if possible, to avoid 

 the trouble of frequently moistening the earth in 

 my nests, I supplied one of my communities with a 



