Galls caused by the larvae of Cecidomyia marginem- 

 torquens Wtz. 



on 



the leaves of Salix viminalis Linn. 

 PLATE 81. 



Synonymy of Insect. 



Cecidomyia marginem-torquens Bremi. 

 ., „ Theobald. 



Haiutat of the Common Osier.— It grows in swampy 

 places and along the sides of streams ; it will also 

 grow to a good-sized tree in drier situations. Common 

 throughout Europe. 



The Gall is formed by the margins of the leaf being rolled 



along the under surface towards the mid-rib. 

 Position.— Along the margins of the leaf 

 Manner of Growth.— Glabrous ; glossy ; coalescent. 

 Colour. — Pale green, yellow, red, purple, chocolate-brown. 



Average Dimensions of a Mature Specimen. 

 Length, 50 mm. ; breadth, 2 mm. 



May be sought during the months of June to October. 

 The Growth is complete by the end of August. 

 The Typical Condition of the gall is multilarval. 

 The Larv.^ pupate in the ground. The imagines emerge 

 during the spring. 



The two leaves in the centre of the illustration exhibit the 

 appearance of the under surface, the other two the upper sur- 

 face. It is very seldom that the margins roll sufficiently to 

 meet each other. On some bushes of Salix viini7ialis almost 

 every leaf is galled by this Cccid. 



The gall is also figured by F. V. Theobald, " British Flies," 

 p. 71. 



The illustration is of specimens gathered at Hastings by the 

 author. 



194 



