32 



After a number of preliminary experiments of one kind or another 

 I used the following simple device to serve my purpose. I took an 

 ordinary spindle-file with a base 2^ inches square, from the center of 

 which extended upward, 7 inches in height, a cylindrical rod ^ inch 

 in diameter. On the sharp point of this rod I stuck a circular piece 

 of cork, I inch in diameter, which served as a support for a bottle 

 containing sugar dissolved in water. Before placing the bottle of 

 sugar-water on the cork I would cause the ants to form a trail to the 

 bottle sitting on my desk ; then I would replace the bottle with the 

 file having the bottle on top, usually with 50 to 100 ants feeding 

 from it. So many of these ants in wandering back from the bottle 

 of sugar-water would meet the ants at the base of the file, that soon 

 the trail would be continued up the rod to the bottle. 



EXPERIMENT NO. I 



After a distinct trail was formed, I removed the cork with the 

 bottle just long enough to thrust the rod through the center of two 

 pieces of clean white note-paper, 2;^ inches square, one of which I 

 placed one third, the other two thirds, the distance up the rod, so 

 that the whole apparatus now had the appearance shown in the figure. 

 In order to get down, the ants now had to go out to 

 the edge of the papers on the upper side and return to 

 the rod on the under side. It was several hours be- 

 fore they formed a distinct trail, since they wandered 

 about in confusion on the upper side of the papers and 

 did not like to go over the sharp edges. When the 

 trail was formed it led down the side of the bottle 

 ^::::^ nearest the nest, down the rod on the same side, then 

 in a straight line out to the middle of the edge of the 

 paper towards the nest, back to the rod on the under 

 -^^ side in the same line and over the lower paper in the 

 same way, so that the trail on it was exactly beneath 

 =r^ the one on the upper paper, then on down the rod and 

 back to the nest. 



After a good trail was formed I turned the top paper a few de- 

 grees to the right when no ants were on it. The next ants that 

 reached the paper, both from above and from below, instead of fol- 

 lowing in the same direction followed the old trail, which extended 

 at an angle of a few degrees from its former direction. I then turned 

 the lower paper a few degrees to the left with the same result, that 

 is, the ants followed the trail. I continued turning the top paper to 



