GALL MITES. 351 



CASE same species of Phytoptus that he detected in the lime tree 

 nail-gall also in the malformed and distorted buds of the hazel. 

 Duges found the same mite (or at least what has been supposed 

 and assumed to be the same mite) in a similar gall, or Salix alba, 

 and Siebold found it among the hairs of some species of Erineum, 

 and named it Eriophyes. Now if these were really the same 

 species there would be here a want of that restricted and definite 

 relation between the gall produced, the plant on which it is pro- 

 duced, and the insect producing it, which we have hitherto found 

 to be constant in the relation of gall and gall-maker. An insect 

 that is found at one time in the distorted buds of the hazel, 

 and at another in the galls of the willow leaf, and at a third in 

 the galls of the lime leaf, cannot, one would think, well be the 

 maker of all three. In all cases that we know of, where galls of 

 a special and distinct form are produced, they are invariably the 

 work of some specific insect, told off, as it were, for that special 

 purpose. In other words, the same insect does not make two 

 different kinds of galls, and the same gall is never made by two 

 different kinds of insects, nor on two different kinds of trees, nor 

 does it at one time make a gall and at another time make none : 

 its habits of life are fixed. It is either always a gall-maker or 

 never. On the other hand, as we have seen, the galls made by 

 Phytopti differ somewhat from other galls, and it may be that the 

 same irritation which produces one form of excrescence on one 

 plant may produce another on a different one, through the differ- 

 ence in their constitution ; or, it may even produce a gall on one 

 and not on another ; but the more probable conclusion seems to 

 be that the observers referred to may have confounded different 

 species. 



Another very difficult point of inquiry, especially with a view 

 to preventing or curing their attacks, is to ascertain their habits. 

 How does such an insect which, apparently, is entirely a vegetarian, 

 and depends for its food on the sap of young leaflets or leaves, pass 

 the winter when the leaves are all gone ? This we are able to 



