410 Insect Architecture. 



species of calyx or cup of leaf-scales, as occurs also in the 

 well-known gall called the oak-apple. 



We were anxious to watch the proceedings of these flies 

 in the deposition of their eggs, and the subsequent develop- 

 ments of the gall-growths ; and endeavoured 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 trees, 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. (J. R.) 



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 after- 

 wards advert. 



Oak-apple Galls, one being cut open to show the vessels running to granules. 



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

 galls formed by insects ; and this, when compared 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 is commonly as large as a 

 walnut or small apple, rounded, but not quite spherical, the 

 surface being irregularly depressed in various places. The 

 skin is smooth, and tinged with red and yellow, like a ripe 



