34 



EXPERIMENT NO. 3 



Can ants of this species recognize a trail laid down by other in- 

 dividuals belonging to the same or to another colony? 



It would seem in the highest degree improbable that each one of 

 these hundreds of ants following the trail did so only after it had 

 found the food independently or had followed other ants and laid 

 down its own trail, but Miss Fielde in "Further Study of an Ant" 

 ( 1901 ) makes the statement concerning another species, Aphcenogaster 

 fulva picea, that each ant lays down its individual trail, which can 

 not be recognized by other ants of the same colony. In order to 

 test this point with M. pharaonis I brought seven ants from another 

 room of the building and placed them, one at a time, on one of the 

 cardboard disks. In every instance the ant wandered about until it 

 struck the trail, which it then followed, sometimes to the nest and 

 sometimes to the food. To be sure, the ant did not in every instance, 

 especially when excited, recognize the trail the first time it struck 

 it, but almost without exception the trail was recognized sooner or 

 later and followed. It is very improbable that these ants had been 

 on the trail before ; but to make the test more sure I isolated a num- 

 ber of them for several days, during which I caused trails to be 

 formed on new disks. Placing these ants on the disks I found that 

 they followed the trail just as the others had done. In each instance 

 I was careful to place the ants to be tested on the disks at a time 

 when there were no other ants there. These experiments were also 

 to serve another purpose and will be referred to again. 



To find out whether ants from one colony could recognize a trail 

 laid down by ants of a different colony, I had a friend whose pantry 

 was infested by this same species, and whose house was at least a 

 quarter of a mile from the insectary, bring me a number of them in 

 a bottle. I found that they recognized the trail just the same and 

 started to follow it, but that they were invariably attacked and killed 

 when thev met the other ants. 



EXPERIMENT NO. 4 



To determine the length of time a trail can be recognized after it 

 has ceased to be used. 



January 2$. — 3 105 P.M. I remove the top disk, B, having pre- 

 viously marked the position of the trail by placing a small ink spot 

 on either side of it. 



4:15 P.M. I replace disk B in such a way that the trail leads out 

 in the opposite direction from what it did before, and in the opposite 



