398 INSECT ARCHITECTURE. 



consider them as such, and predict that they formed 

 the nidus of some species of insects. In more 

 instances than one we nave felt so strongly assured of 

 this, that we have kept several specimens for some 

 months, in nurse-hoxes, expecting that in due time the 

 perfect insects would be disclosed. 



One of these pseudo- galls occurs on the common 

 bramble (Rubus fruticosus), and bears some resem- 

 blance to the bedeguar of the rose when old and 

 changed by weather. It clusters round the branches 

 in the form of irregular granules, about the size of a 

 pea, very much crowded, the whole excrescence being 

 rather larger than a walnut. We expected to find 

 this excrescence full of grubs, and were much sur- 

 prised to discover, upon dissection, that it was only a 

 diseased growth of the plant, caused (it might be) 

 by the puncture of an insect, but not for the purpose 

 of a nidus or habitation.* 



Another sort of excrescence is not uncommon on 

 the terminal shoots of the hawthorn. This is in 

 general irregularly oblong, and the bark which covers 

 it is of an iron colour, similar to the scorias of a black- 

 smith's forge. When dissected, we find no traces of 

 insects, but a hard, ligneous, and rather porous tex- 

 ture. It is not improbable that this excrescence may 

 originate in the natural growth of a shoot being 

 checked by the punctures of aphides, or of those grubs 

 which we have described (page 389). 



Many of those excrescences, however, are probably 

 altogether unconnected with insects, and are simply 

 hypertrophic diseases, produced by too much nourish- 

 ment, like the wens produced on animals. Instances 

 of this may be seen at the roots of the holyhock 

 (Allhea rosea) of three or four years' standing ; on 

 the stems of the elm and other trees, immediately 



