Galls caused by the larvae of Saperda populnea Linn. 



on 



the boughs of Populus tremula Linn. 

 PLATE n. 



Synonymy of Insect. 



Habitat of the Aspen.— This tree grows well in coppices, 

 woods, and forests ; it may also frequently be seen in a 

 flourishing condition on the outskirts of a wood. 



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 twigs, small branches, and sometimes on 

 the main stem. 



Manner of Growth.— Singly ; seldom coalesced. 



Colour.— Same as unaffected part of branch. 



Average Dimensions of a Mature Specimen. 

 Length, 25 mm.; girth, 60 mm. 



M.\Y BE sought during any month in 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 gall. The imago emerges during 

 June. 



These galls are very local. So far as my observations have 

 extended, they are nowhere plentiful, even in districts where 

 they do occur. The south-eastern counties of England appear 

 to be the most favoured. They are, however, found in the 

 midland and .several other counties. 



The gall is also figured by Mosley, " Nat. Journal," June, 

 1898 (from specimens supplied by the author). 

 71 



