82 OSIERS AND WILLOWS 



subsequently fail to develop normally and become 

 bunched together or form a distinct rosette. These 

 galls are usually known as buttons or button tops. 

 In the galls are found one or more minute orange-red 

 larvae, which, when full fed, either pupate in the galls 

 or fall out and pupate in the soil. There appear to be 

 two generations in the year, and it is believed that 

 the winter is spent as a larva in the galls, but statements 

 on these points do not always agree. 



The most injurious species is known as Cecidormyia 

 heteroUa, and may be recognised by the fact that the 

 buttons contain many larvae and are rather shapeless, 

 not as a rule in the form of a neat rosette. A second 

 species, Cecidormyia rosaria, produces galls which may 

 be distinguished by the fact that they each contain 

 only one larva and are rosette-shaped. 



The injury done by these insects is decidedly serious, 

 since attacked rods are stunted and may also be 

 " bushy topped." 



There are several other species of gall midge which 

 attack willows, but mention need only be made of the 

 willow wood midge, Cecidormyia saliciperda. The larvae 

 of this insect live in burrows in the rods, usually near 

 the base. They pupate in the burrows and the flies 

 emerge, through minute pin-holes in the bark. The 

 winter is spent in the larval condition in the rods. 



Attacked rods which are more often of two years' 

 growth are of little value, as the attacked portion is 

 weak and must be cut away. 



Methods of Control. No suggestions as to practical 

 methods of control have been given in the preceding 

 sections since the few forms of treatment known may 

 be applied in the case of attack by several kinds of 

 pest. Notes under this heading may be divided into 



