384 INSECT ARCHITECTURE. 



We were anxious to watch the proceedings of these 

 flies in the deposition of their eggs, and the subse- 

 quent developments of the gall-growths ; and endea- 

 voured for that purpose to procure a small oak plant 

 in a garden-pot ; but we did not succeed in this : and 

 though they alighted on rose and sweet-briar tries, 

 which we placed in their way, we never observed that 

 they deposited any eggs upon them. In a week or 

 two the whole brood died, or disappeared.* 



There are some galls, formed on low-growing 

 plants, which are covered with down, hair, or wool, 

 though by no means so copiously as the one which 

 we have just described. Among the plants so affected 

 are the germander speedwell, wild-thyme, ground- 

 ivy, and others to which we shall afterwards advert. 



The well-known oak-apple is a very pretty example 

 of the galls formed by insects ; and this, when com- 

 pared with other galls which form on the oak, shows 

 the remarkable difference produced on the same plant 

 by the punctures of insects of different species. The 



Oak-apple tjalls, one being cut open to show the vessels turning to 

 Granules. 



