1909.] 



Gall Flies on the Oak. 



293 



tity of fibre and become well established. Trees that have been 

 root-pruned will make quite sufficient wood growth for their 

 well-being, and at the same time develop fruit spurs freely, to 

 be followed, climatic conditions permitting, by a good crop of 

 fruit. 



The following note has been supplied to the Board by Dr. 

 R. Stewart MacDougall : — 



The Cynpidce, or Gall Flies, are a family of minute 

 Hymenopterous insects whose larvae live in galls, or in some 

 cases are parasitic in the bodies of 

 Gall Flies on the other insects. 



Oak. The true gall fly lays an egg or 



eggs in the live tissue of the plant. 

 The me ri stem tissue of the plant is stimulated by the 



fig. i. — Galls due to Neurotenis lenticularis. 



presence of the larvae and their puncturings and secretions, 

 and the result is the swelling known as a gall. Here the 



