46 THE POPULAR SCIENCE MONTHLY. 



to affect the conclusion. The former nest contains about two hun- 

 dred, the second about four hundred individuals ; but as they are 

 somewhat torpid, and there are no larvse to be fed, much food is 

 not required. In each case only two or three individuals came out 

 for food, each about twice a day, though some days they did not 

 come out at all. Thinking that possibly these specimens were un- 

 usually voracious, or in some other way abnormal, I imprisoned the 

 foragers belonging to one of the nests. The following day two 

 others came out for food, and continued coming for several days. 

 I then imprisoned them also, when two others came out showing, 

 I think, that the community requires food, and that it was the 

 functions of certain individuals to obtain it. 



One of the most interesting problems about ants is, of course, to 

 determine the amount of their intelligence. In order to test this, 

 it seemed to me that one way would be to ascertain some object 

 which they would clearly desire, and then to interpose some obstacle 

 which a little ingenuity would enable them to overcome. With 

 this object in view, I placed food in a porcelain cu^j on a slip of glass 

 surrounded by water, but accessible to the ants by a bridge, consist- 

 ing of a strip of paper two-thirds of an inch long and one-third wide. 

 Having then put a F. nigra from one of my nests to this food, she 

 began carrying it off, and by degrees a number of friends came to 

 help her. I then, when about twenty-five ants were so engaged, 

 moved the little paper bridge slightly, so as to leave a chasm just 

 so wide that the ants could not reach across. They came to the 

 edge and tried hard to get over, but it did not occur to them to push 

 the paper bridge, though the distance was only about one-third of 

 an inch, and they might easily have done so. After trying for about 

 a quarter of an hour they gave up the attempt, and returned home. 

 This I repeated several times. Then, thinking that paper was a 

 substance to which they were not accustomed, I tried the same with 

 a bit of straw one inch long and one-eighth of an inch wide. The 

 result was the same. I repeated this twice. Again I placed par- 

 ticles of food close to and directly over the nest, but connected with 

 it only by a passage several feet in length. Under these circumstances 

 it would be obviously a saving of time and labor to drop the food 

 on to the nest, or at any rate to spring down with it, so as to 

 save one journey. But, though I have frequently tried the experiment, 

 my ants never adopted either of these courses. I arranged matters 

 so that the glass on which the food was placed was only raised one- 

 third of an inch above the nest. The ants tried to reach down, and 

 the distance was so small that occasionally, if another ant passed 

 underneath just as one was reaching down, the upper one could step 

 on to its back, and so descend ; but this only happened acciden- 

 tally, and they did not think of throwing the particles down, nor, 

 which surprised me very much, would they jump down themselves. 



