THE MOUND OF POGONOMYRMEX RADIUS LATKL. 



i6 7 



duced into the tube with the male. They copulated immediately. 

 As soon as coition was over, the female was removed and a 

 fresh female introduced. This was repeated until the male would 

 no longer mate. The greatest number of females served by the 

 same male was five ; the least, four. After the last successful 

 coition, when a fresh female was added, the male would attempt 

 to copulate, but in vain. 



These experiments show, conclusively, that the same female 

 may mate with several different males and that the same male 

 may serve several females. As to the number of services that 

 either may give or accept, these experiments do not give a final 



FIG. 7. Mound of P. badius, surface view, a, entrances ; b, debris, mostly plant 

 matter, from the nest. The top is covered with pebbles. On the edge there are a few 

 stalks of grass. Greatest length, 40 in.; greatest width, 39 in. 



answer ; for there was no way of being sure that the female cap- 

 tured on the nest had not previously been served ; nor could I 

 be absolutely certain that the male had not visited some other 

 mound and copulated before arriving at the nest. 



From the above description, it seems evident that the mound 

 of this species is a device for promoting cross-fertilization^ The 

 large, conspicuous, expanse of barren land in the midst of vege- 

 tation serves as a stimulus to attract the flying male. Whether 

 this is to be regarded as a tropism or an ordinary reflex is more 

 than the experiments answer. That it is an instinctive response 

 is self-evident. 



