DIPLOSIS DRYOBIA. 147 



Diplosis dryobia, Low. 

 (Plate LXIII.) 



Diplosis Lieheli, Kieffer. 



Position of gall. — The margins of the lobes of the leaf. 



Manner of growth. — Glabrous, glossy, crescent-shape. 



Colours. — Pale green, green, light brown, dark brown, chocolate. 



Average dimensions of a mature specimen. — Length, 

 15 mm. ; breadth, 2 mm. 



May be sought during the months of June to September. 



Growth is complete l)y the end of July. 



The typical condition of the gall is unilocular but multilarval. 

 Usual number of larvae, 4. 



The larvae pupate in the ground. The imagines emerge 

 during the spring. 



Tlie margins of the lobes are curved upwards and 

 folded down upon tlie upper surface of tlie blade, form- 

 ing a thickened roll within which the larvae live. The 

 edge of the recurved portion presses very closely upon 

 the surface of the leaf, preventing the intrusion of other 

 small creatures, such as mites, etc., and retaining the 

 larvEe until fully grown when it either gapes to allow 

 them to fall to the ground, or they push their way out. 

 The affected area is not easily noticeable from the other 

 surface of the leaf. 



A species of Eriophyidge, Ejntrimerus cri status, 

 Nalepa, a mite which occurs in Central Europe, 

 causes the leaf-margins of Q. puhescens to curl in a 

 similar manner ; the folded portions, however, affect 

 tlie under- surface of the leaf as well as continuing to 

 the extremity of each indentation of the leaf. There 

 is no change of colour in the rolled portions. 



It is probable that this species may be discovered in 

 Britain. 



The dimensions of the mites are : male, 0'12 mm. 

 long, 0'046 mm. broad; the female, 0*17 mm. long, 

 0'057 mm. broad. 



Plate LXIV is introduced from ' Zur Kenntniss der 

 Gattung Trimerus,' by the kind permission of Dr. 

 Xalepa, Vienna. 



