GALL-FLIES. 381 



bedeguar and the oak artichoke, causing leaves to 

 spring out, of a shape totally different from the other 

 leaves of the tree, and arranged very much like the 

 petals of a rose. Decandolle says it is found chiefly 

 on the Salix helix, S. alba, and S. riparia* 



A production very like that of the rose-willow 

 may be commonly met with on the young shoots of 

 the hawthorn, the growth of the shoot affected being 

 stopped, and a crowded bunch of leaves formed at 

 the termination. These leaves, beside being smaller 

 than natural, are studded with short bristly prickles, 

 from the sap (we may suppose) of the hawthorn 

 being prevented from rising into a fresh shoot, and 

 thrown out of its usual course in the formation of 

 the arms. These bristles appear indiscriminately 

 on both sides of the leaves, some of which are bent 

 inwards, while others diverge in their natural manner. 



This is not caused by the egg or grub of a true 

 gall-fly, but by the small white tapering grub of 

 some dipterous insect, of which we have not ascer- 

 tained the species, but which is, probably, a ceci- 

 domyia. Each terminal shoot is inhabited by a 

 number of these — not lodged in cells, however, but 

 burrowing indiscriminately among the half-withered 

 brown leaves which occupy the centre of the pro- 

 duction.! 



A more remarkable species of gall than any of 

 the above, we discovered in June, 1829, on the 

 twig of an oak in the grounds of Mr Perkins, at 

 Lee, in Kent. When we first saw it, we imagined 

 that the twig was beset with some species of the 

 lanigerous aphides, similar to what is vulgarly called 

 the American or white blight {aphis lanata;) but 

 on closer exammation we discarded this notion. The 

 twig was indeed thickly beset with a white downy, 



* Flore Fran^. Disc. Pr. liminaire. 

 t J. R. 



