2IO JOHN L. PRICER. 



side toward the nest, this group began to advance slowly into 

 the disturbed territory. After much retracing of steps they suc- 

 ceeded in about three minutes in crossing this area, which was 

 only about one foot in diameter, and they then hurried on their 

 way unhesitatingly. 



Obsei'vation 2. — About fifty feet of the path of this colony from 

 the nest to the aphid tree lay through a dense weed patch. 

 Early in the summer I had smoothed out with a hoe a narrow 

 path in a fairly direct line from the nest to the aphid tree, and by 

 repeatedly passing along this path myself, I kept it worn smooth 

 all summer. I repeatedly observed that the ant caravan used 

 this path only at points where it happened to coincide with a 

 perfectly direct line between the point at which they entered 

 the weed patch and the point at which they emerged from it. 



On the afternoon of August 4, 1906, some men came with a 

 plow and tried to plow the weeds under. The weeds were three 

 or four feet high, and when the plowing was finished the lot 

 seemed to me an impassable barrier to the movement of the 

 ants. That evening, as the ants began to pour forth from the 

 nest for their night's work, great excitement ensued when they 

 reached the edge of the plowed ground, which was about five 

 feet from the nest. Soon a space about one foot wide and reach- 

 ing from the nest to the plowed ground was literally black with 

 ants, all running back and forth and behaving very much as 

 people do in case of a fire in a city. After about twenty minutes 

 of confusion the vanguard began to advance slowly into the 

 plowed ground, and in just two hours they had reached the 

 other side. During all this time about one hundred and fifty 

 ants which had started from the aphid tree to the nest were col- 

 lected near the border of the plowed ground, but not one of 

 them ventured as much as an inch into it. The next day and 

 evening they were traveling back and forth just as if nothing had 

 happened, and the path that they followed was so straight that 

 when I stretched a line across between the two points of entrance 

 no ant was seen to be more than five inches to either side of the 

 line anywhere along the course. A decided curve was made in 

 the path, however, after reaching smooth ground on the side 

 toward the aphid tree. 



