Galls caused by the larvae of Cecidomyia salicis Schrk. 



on 



the twigs of Salix cinerea Linn. 

 PLATE 28. 

 Synonymy of Insect. 



Cecidomyia salicina Bouche. 

 „ gallanun-salicis. 



„ Degeeri Bremi. 



„ argyrosticta Macq. 



Habitat of the Grey Sallow. — Common throughout 

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

 open woods, and in thickets and hedges. 

 The Gall is formed by the larvs feeding upon the pith 



and causing the woody cells which surround it to swell. 

 Position. — On the top twigs of the tree. 

 Manner of Growth. — Separately, seldom more than one 



on a twig ; glabrous. 

 Colour. — Same as the twig upon which it is found. 

 Average Dimensions of a Mature Specimen. 



Length, 20 mm. ; girth, 36 mm. 

 May be sought during any month in the year. 

 The Growth is complete by the end of October. 

 The Typical Condition of the gall is plurilocular. Usual 



number of cells, 20. 

 The Larv^ pupate in the gall. The imagines emerge during 

 May. 



The peculiar lemon-like shape of these galls distinguishes 

 them very readily from other willow-galls. They occur 

 also on Salix aurita. The larvae live in the centre of the 

 swelling, feeding on the pith ; the number in a gall varies 

 from two or three to thirty. The larval chambers are irregu- 

 larly elongated, and have very thin walls. When fully fed the 

 larvjE work their way towards the exterior of the gall, and upon 

 emersion of the imago about half of the puparium is left 

 projecting from the hole. 



The illustration is of specimens gathered at Hastings by 

 the author. 



