ANTS KEEPING APHIDES. 61 



principles, such a class of facts is to be met ; for it is cer- 

 tainly difficult to understand the manner in which this 

 instinct, so beneficial to the ants, can have arisen in the 

 aphides, to which it does not appear, at first sight, to offer 

 any advantages. Mr. Darwin meets the difficulty thus : 

 ' Although there is no evidence that any animal performs 

 in action for the exclusive good of another species, yet 

 each tries to take advantage of the instincts of others ;' 

 and ' as the secretion is extremely viscid, it is no doubt a 

 convenience to the aphides to have it removed ; therefore 

 probably they do not excrete solely for the good of the 

 ants.' l 



Some ants which keep aphides build covered ways, or 

 tunnels, to the trees or shrubs where the aphides live. 

 Forel saw a tunnel of this kind which was taken up a wall 

 and down again on the other side, in order to secure a 

 safe covered way from the nest to the aphides. Occasion- 

 ally such covered ways, or tubes, are continued so as to 

 enclose the stems of the plants on which the aphides live. 

 The latter are thus imprisoned by the walls of the tube, 

 which, however, expand where they take on this additional 

 function of stabling the aphides, so that these insects are 

 really confined in tolerably large chambers. The doors of 

 these chambers are too small to allow the aphides to escape, 

 while large enough for the ants to pass in and out. Forel 

 saw such a prison or stable shaped like a cocoon, and 

 about a centimetre long, which was hanging on the branch 

 of a tree, and contained aphides carefully tended by the 

 ants. Huber records similar observations. 



Sir John Lubbock has made an interesting addition to 

 our knowledge respecting this habit as practised by a 

 certain species of ant (Lasius flavus\ which departs in a 

 very remarkable manner from the habit as practised by 

 other species. He says : ' The ants took the greatest care 

 of these eggs, carrying them off to the lower chambers 

 with the utmost haste when the nest was disturbed.' But 

 the most interesting of Sir John Lubbock's observations 

 in this connection is new, and reveals an astonishing 



1 Origin of S^e.-ica, 6th ed. pp. 207-8. 



