care of their helpless charges, would enable us to compare the various 

 substances tested in respect to the intensity and persistence of their 

 repellent effects. 



The apparatus used (which we may call the cage, Fig. 1) was 

 essentially a shallow, water-tight glass tray, or basin, made by build- 

 ing a wall half an inch high, with putty covered by strips of glass, 

 around the edge of a pane of glass 16 X 12 inches, inside which another 

 pane of glass, 8 X 12 inches, was supported at the corners by pieces 

 of glass stuck on with balsam. This latter plate we will call the base 

 of the tiest (b). Its top was a trifle below the upper edge of the walls of 

 the tray, so that water poured into the latter until it reached the 

 under-surface of the plate would surround it as by a moat, which 

 prevented the escape of the ants placed upon it. Under the center of 



Fig. 1 



the transparent bottom of the cage was placed a sheet of plain white 

 paper with concentric circles drawn upon it, the smallest a quarter 

 of an inch in diameter, and the succeeding circles separated from 

 each other by an eighth of an inch. By the aid of these circles one 

 could tell at a glance the exact distance from the center to which any 

 ant had withdrawn. Upon the center of the base was placed the 

 repellent, and over this a piece of orange glass, or cover, supported 

 at its corners by bits of cork just thick enough to allow the ants to 

 pass under the cover conveniently. The space between the cover and 

 the base is the nest (c). The orange covers differed in size from 2 X 2y^ 

 inches to 2^ X 3, the latter being the size used in the following experi- 

 ments unless other dimensions are given in the descriptions. In some 

 of the cages used a circle three inches in diameter was cut out of the 



