ABIDING CITIES 193 



and sip this pittance of nectar, leaving the richer 

 and more valuable stock of honey in the actual 

 blossom to be rifled by the bees which are the 

 honoured guests and allies of the vetches. Nature 

 is all full of such quaint plots and counterplots. 

 One example occurs in a South American tree, so 

 very remarkable that I cannot pass it by even in 

 this hasty notice. 



A certain ant, very common in Brazil, has the 

 habit of cutting large round pieces out of the leaves 

 of trees, which it then conveys to its nest for the 

 purpose of growing fungi upon them in human 

 language, making tiny mushroom-beds. Now, this 

 habit is naturally obnoxious to the trees, which 

 produce the leaves for their own advantage, not 

 for the sake of leaf-cutting ants which hack and 

 rob them. To guard against the burglarious leaf- 

 cutters, accordingly, one clever South American 

 acacia has hit upon an excellent plan of defence. 

 It produces curious hollow thorns ; while each 

 leaflet has a gland at its base which secretes honey. 

 Into these hollow thorns, colonies of a small and 

 harmless ant migrate, and take up their abode 

 there. They live off the honey at the base of the 

 leaflets. They thus acquire a vested interest in the 

 acacia tree, which is their home and territory ; and 

 whenever the leaf-cutting ants attack the acacia, 

 the little occupants of the thorns and owners of 

 the honey-chambers pour out upon them in their 

 thousands, and compel the invaders to beat a hasty 

 retreat with heavy losses. Thus the cunning tree 

 supplies its insect body-guard with board and 



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