58 THE ARGENTINE ANT. 
will frequently encircle the spot which they ultimately hope to attain. 
They will never attempt to avoid a hand threatening from any 
direction as a spider will do, but will continue going ahead until 
their antennae touch the obstacle. The manner in which they 
religiously follow their trails and the confusion which results when 
these trails are destroyed proves that they do not trust to a sense of 
sight in traveling. This is illustrated again hj the fact that they are 
active all night in the darkest situations. 
HEARING. 
The sense of hearing in these insects is not acute, even if indeed it 
be developed at all. The ants are not disturbed by ordinary noises, 
such as talking or working about the nests. If, however, one emits 
a loud shout within a few inches of the formicary, or fires a pistol 
near it, the ants are thrown into the confusion and excitement 
characteristic of them when disturbed. It seems not impossible 
that in such cases they have detected actual vibrations of the surface 
on which they are located, due to the action of the sound waves. 
Strangely enough, in situations where loud noises and vibrations are 
of constant occurrence, the ants become accustomed to them. Thus 
at New Iberia, La., we found ant colonies between and under the 
ties of a railroad track over which many trains passed daily. 
CANNIBALISM. 
Cannibalism in any form is extremely rare in the case of this 
species, and true cannibalism has not yet been observed. The only 
thing at all approaching it was observed in the case of a colony kept 
in our formicarium, the workers of which developed a habit of eating 
the eggs as fast as they were deposited by the queen. This colony 
was established in an artificial formicary on November 27, 1907, and 
from that time until the early part of July, 1908, larvae were reared 
more or less continuously and in the usual numbers. In July it was 
noticed that the number of immature stages became steadily smaller, 
and on July 28 a quick removal of the cover from the cage disclosed 
several workers in the act of eating eggs. Thinking that this might 
be due to lack of sufficient food of an animal nature fresh meat was 
at once furnished the colony and was thereafter kept continually 
accessible. In spite of this the egg-eating habit continued until 
November 5, 1908, all eggs being eaten within a few hours after their 
deposition by the queen. By this time the number of workers in the 
colony had been reduced to six, and by November 1 1 the queen and 
remaining workers were dead, the colony having apparently been 
exterminated through lack of any maturing workers to replace those 
dying from old age and accident. 
