Galls caused by the larva; of Nematus bellus Lad. 



on 



the leaves of Salix caprea Linn. 



PLATE 110. 

 Synonymy of Insect. 



NonaUis pedunctdi Cam., Kerner. 

 „ viiiiinalis Br. and Lad. 

 Habitat of the Sallo\v or Goat-willow.— Very common 



throughout Britain by the sides of streams, marshy places, 



damp open woods, and in thickets and hedges. 

 The Gall is formed by the action of the larva upon the 



tissues of the leaf. 

 Position.— On the under surface of the leaf. 

 Manner of Growth. — Singly and glabrous, sometimes 



coalescent ; pubescent. 

 Colour. — Greenish yellow, with small red or reddish brown 



spots. 

 Average Dimensions of a Mature Specimen (globular 

 form). 



Height, 6 mm.; girth, i8 mm. 

 May be sought during the months of June, July, and 



August. 

 The Growth is complete by the end of July. 

 The Typical Condition of the gall is unilocular and 



unilarval. 

 The Larva pupates away from the gall. The imago emerges 



during the spring. 



The shape of these galls is variable, some being globular, 

 some pyriform, and others conical. They are always firmly 

 attached by the base to the under surface of the leaf, and 

 are mostly close to or upon the mid-rib. On the upper surface 

 of the leaf is a semicircular depression, the elevated margins of 

 which are usually dull brown in colour. 



The gall is also figured by Cameron, " British Phytophagous 

 Hymenoptera," vol. i , plate v. ; Kerner, " Nat. Hist, of Plants," 

 vol. ii., p. 531. 



251 



