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 have felt so strongly assured of this, that 

 we have kept several specimens for some months, in 

 nurse-boxes, expecting that in due time the perfect 

 insects would be disclosed. 



One of these pseudo-galls occurs on the common 

 bramble {Rubiis fruiicosus), and bears some resem- 

 blance to the bedeguar of the rose when old and changed 

 by weather. It clusters round the branches in the tbrm 

 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 surprised 

 to discover, upon dissection, that it was only a dis- 

 eased 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 scoriae of a black- 

 smith's force. 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 

 {Aiihea rosea) of three or four years' standing; on 

 the stems of tlic elm and other trees, immediately 



=^ J. R. 



