12 The Scottish Naturalist. 



blades. When very young, they are of a very light green 

 colour, but as they reach maturity this gives place to a deep red 

 above, and a paler red or light green beneath. The number on 

 a single leaf varies from one to thirteen, which is the most I 

 have found. A single larva resides in each gall. (PI. I., fig. 2). 



Salix alba L. The galls only differ from the former in being 

 whitish-green or light red, and in the underside being hairy. 

 (PI. I, fig. 3.) 



Salix caprea L. They are somewhat oval, dark shining green 

 above, and very hairy underneath. This gall is not very common. 



Salix ci7ierea L. These galls I have only found on the banks 

 of Loch Lomond. They are oblong, dark green, like those on 

 S. caprea, but much smaller, and slightly hairy. 



Although the galls are so extremely common, yet they are 

 local to a remarkable degree, and the insects show a strange 

 preference for particular trees. Thus one tree will be completely 

 covered with galls, while another some yards distant will not 

 have a single specimen on it. According to my experience 

 they are commonest on the willows at a distance from water, 

 and when they do appear on trees growing on river banks, it is 

 on the land-side they are found. Jhis appears to be also the 

 case with its coleopterous inquiline Balaninus brassicce. The 

 galls, containing larvae in all stages of growth, may be found on 

 the trees from the end of May to the end of October. 



The perfect insects make their appearance about the 20th of 

 May (kept inside the house, they come out in March), and the 

 females shortly afterwards proceed to deposit their eggs. This 

 they do in the undeveloped leaf-buds, laying the eggs in several 

 leaves by one operation. In due time the young leaves reach 

 their proper size and the galls grow out along with them. The 

 eggs are also deposited in young but fully developed leaves, and 

 later on in the season on old and rather dry ones. The 

 majority, if not the whole, of these latter always produce small 

 and irregular galls, which very rarely or never contain larvae. 

 It may therefore be concluded that for the proper growth of the 

 galls, and the well-being of the larvae, it is necessary that the ova 

 should be deposited in young and growing leaves. 



The egg, after being laid, swells to about double its first size. 

 It is a minute, oblong, transparent white object, about i-5oth- 

 inch in length, frequently with a slight curve in one of its sides. 



