Ants and Mites 



mites have many hairs and a comparatively large but 

 variable cavern. (When we say large, we mean about 

 one-sixth of an inch.) 



So the interesting question arises, are the effects of 

 mite scraichings and secretions inherited ? The forma- 

 tion of hairs and the same sort of pocketing of leaf tissue 

 is one of the commonest characters of galls, If the 

 hairy pockets appear on a young leaf which has never 

 seen a mite, then there is an inheritance of these effects. 



There are other cases just as interesting and on which 

 a violent controversy has been carried on. The most 

 remarkable of all concerns a certain genus of South 

 American plants called Tococa, and which lives in the 

 Amazon valley. 



The traveller Spruce, forty years ago, wrote an inter- 

 esting paper about Tococa, of which he knew at least 

 nineteen species in the Amazon valley. These shrubs, 

 with one exception, grow in that part of the valley which 

 is regularly overflowed for months together by the 

 annual inundation of the " white " or silt-laden water. 



They are remarkable for a very curious swollen leaf- 

 stalk. This expanded part is hollow and is inhabited 

 by fierce ants, which swarm out and bite severely any 

 traveller that meddles with the shrubs. Indeed Spruce 

 found it very difficult to get satisfactory specimens of 

 Tococa in consequence of this bodyguard of ants. He 

 points out also that during the annual floods, the ants 

 are saved by these hollow residences, which are often 

 above the level of the water. 



But the one species which is found outside the in- 

 undation level has no such swellings and apparently no 

 bodyguard of ants. In the original paper Spruce goes 

 on to say that he had occasionally found in several of the 

 inundated species leaf-stalks which were not inhabited 

 by ants but which nevertheless showed the character- 



206 



