Galls caused by the larvae of Saperda populnea Linn. 



on 



the stems of Salix oaprea Linn. 



PLATE 22. 

 Synonymy of Insect. 



Habitat of the Sallow, or Goat-willow. — Very 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 presence of the larva in the pith 

 causing the surrounding tissues to swell and bulge outwards. 



Position. — On the stem, branches, and sometimes the twigs 

 also. 



Manner of Growth.— Singly ; seldom coalesced. 



Colour. — Same as unaffected part of stem. 



Average Dimensions of a Mature Specimen. 

 Girth, 66 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. 



The Larva pupates in the gall. The imago emerges during 



May. 



The appearance of these galls is somewhat different from 

 those on the aspen caused by the same species of beetle. In 

 the case of the aspen the puncture made by the ? for oviposition 

 results in a scar being formed, but with the willow this does not 

 appear to be the case. The growth of the willow is more rapid. 

 The epidermis does not close over the puncture, and, as the 

 growth of the stem proceeds, a depression is formed. In the 

 lower left-hand corner of the illustration an imago will be seen. 

 It emerged from the hole above it, a short while before the 

 photograph was taken. 



The illustration is of specimens gathered at Hastings by the 

 author. 



74 



