Galls caused by the larvae of Xestophanes brevitarisis 

 Cam. 



on 



the stems of Potentilla tormentilla Sibth. 

 PLATE 43. 



Synonymy of Insect. 



Aulax brevitarisis Opusc. 



Xestophanes tornientillce Schl., Cameron. 



Habitat of the Tormentil. — This plant is common in 

 most parts of Britain, in open places in woods and by the 

 sides of footpaths through them ; it is also found on 

 moors and heaths. 



The Gall is formed by a gradual and persistent accumu- 

 lation of sap around the ova deposited beneath the cuticle 

 of the plant. 



Position.— On the stems. 



Manner of Growth. — Gregarious; conglomerated; sessile; 

 slightly pubescent. 



Colour. — At first, green, later pink, changing to purple, and, 

 when mature, nut-brown. 



Average Dimensions of a Cluster of Mature Speci- 



MEN.S. 



Length, 13 mm. ; breadth, 7 mm. ; girth, 18 mm. 

 May BE sought during the months of June to November. 

 The Growth is complete by the end of October. 

 The Typical Condition of the gall is plurilocular. Usual 



number of cells, 10. 

 The Larv.e pupate in the cells. The imagines emerge 



during the spring. 



These galls are very local in their situations, and are very 

 persistent on the same plants year after year. They may be 

 found in plenty in one spot, but a cluster of the same plants 

 fifty yards away will not be affected. 



The gall is also figured by Peter Cameron, " British Phyto- 

 phagous Hymenoptera" (Ray Society), vol. iv., plate 11. 

 "5 



