Galls caused by the larvae of Agromyza schineri Gir. 



on 



the twigs of Salix cinerea Linn. 



PLATE 23. 

 Synonymy of Insect. 



Habitat of the Grey Willow.— Common throughout 

 Britain, by the sides of streams, in marshy places, damp 

 open woods, and in thiclcets and hedges. 



The Gall is formed by the presence of the larva in the 

 cambium layer causing it to swell and bulge outwards. 



Position. — On the side of the twig. 



Manner of Growth.— Gregarious ; coalescent ; glabrous ; 

 slightly glossy. 



Colour. — Green, with wavy longitudinal lines of paler colour. 



Average Dimensions of a Mature Specimen. 

 Length, 15 mm. ; breadth, 5 mm. 



May be sought during any month of the year. 



The Growth is complete by the end of September. 



The Typical Condition of the gall is unilocular and unilarval. 



The Larva pupates in the ground. The imago emerges 



during spring. 



These galls occur sometimes singly, but generally from two 

 to fifteen on a stem, and are mostly found on young bushes 

 of Salix cinerea. They are oval-shaped, cushion-like swellings 

 which, rising from within the stem, cause the epidermis to 

 crack into longitudinal wavy strands, the edges of which reflect 

 light, imparting to them a whitish colour. This disappears 

 when they are viewed through a lens. Under the same con- 

 ditions small scars may be seen which indicate the holes made 

 for oviposition by the parent fly. 



The illustration is of specimens gathered at Hastings by the 

 author. 



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