ANTS, GREEN FLY, AND SCALE. 



85 



In some cases, as, for example, with root-lice, winged individuals are 

 sometimes not produced for a year or more, and when it is necessary in the 

 course of nature for the plant-lice to migrate from one plant to another 

 the ants carsy them bodily to new pastures, and even prepare in advance 

 places for their occupation. In this they seem to display a most 

 remarkable intelligence, and recognise the necessity for a change when 

 the plants affected by the lice become exhausted of their juices from the 

 numbers of their insect parasites." Perhaps the time selected for 

 transferring the aphides to new pastures is when the ants perceive that 

 their tiny "milch-cows " are becoming dry. 



Truly in that speck of a brain of the ant there seems to be stored up, 

 through inheritance and experience, an amount of knowledge which is 

 perfectly astonishing. 



I regret that personally I have no time to carry out careful experi- 

 ments in connection with this discovery, but it ought not to be difficult 

 for an ant-entomologist to have some plants, usually affected by aphides, 

 under glass cases for convenience of observation and experiment. Then 

 by scattering about some aphides and by introducing some ants to see what 

 they will do, this curious phenomenon of an association between the ant 

 and the aphis, for mutual benefit, may be further studied. There may 

 result, if this discovery be confirmed, some method of preventing the ants 

 having access to a plant, such as rubbing some compound round the base 

 of the stem over which ants would dislike to travel. They might thus 

 be prevented from carrying their nurslings to the tender shoots of the 

 plant. 



It is not improbable that these ingenious ants may have formed some- 

 what similar associations with other insects than aphides. I have some 

 Orange and Lemon plants trained on wires under the glass of a warm house. 

 The under surfaces of their leaves are often infested with some species of 

 scale-insect. Whenever this is the case I have observed that ants are very 

 busy on these Citrus plants. It is not unlikely that some sort of symbiosis 

 may also exist between these ants and this species of scale. I have picked 

 off the scale from the leaves of these Citrus trees, and I am trying an 

 experiment to see if I cannot deter the ants from climbing up them. 

 It is well known that if some ants are crushed by the finger on the line 

 of an ant procession on a wall or other surface, the other ants run away 

 from the scent of their crushed companions ; and the experiment I am 

 trying is to crush some ants between the finger and thumb and rub them 

 round the base of the stem : the rubbing will have to be done on the 

 training wires also, as these ingenious creatures, if they cannot get up 

 one way, may be trusted to find some other way, if possible, to get to the 

 leaves of my Orange and Lemon plants. Now that some advance has 

 been made in the psychology of these clever insects, it may be worth 

 the while of some entomologist with leisure to make further experiments 

 and researches into the life of the ant, with the view of discovering any 

 other form of commensalism that they are capable of originating. In 

 this connection a correspondent in the island of Madeira states that 

 fruit trees there are infected with scale, and, curiously enough, he states 

 that probably ants have a great deal to do with the dissemination of the 

 pest. 



