Galls caused by the larvs: of Diplosis botularia Wtz. 



on 



the leaves of Fraxinus excelsior Linn. 



PLATE 93. 



Synonymy of Insect. 



Cecidoiiiyia fraxini Bremi. 



Diplosis botularia Theobald, Kerner. 



Habitat of the Common Ash. — Common in woods, thickets, 

 plantations, etc., in dry or damp places, and often in hedges 

 near woods. Widely distributed throughout Britain. 



The Gall is formed by the larvae causing irritation to the 

 plant-tissue, and a consequent abnormal swelling. 



Position. — On the rachis and mid-rib of the leaflets. 



Manner of Growth. — Elongated ; glabrous ; glossy. 



Colour. — Pale green, green, ultimately brown. 



Average Dimensions of a Mature Specimen. 

 Length, 45 mm. ; breadth, 5 mm. 



May be sought during the months of June to October. 



The Growth is complete by the end of August. 



The Typical Condition of the gall is plurilocular. Usual 

 number of cells, 6. 



The Larv^ pupate in the ground. The imagines emerge 

 during the spring. 



The inter-leaflet spaces of the rachis are frequently attacked 

 and swollen in a similar manner to that of the mid-rib. Two 

 examples of this may be seen on the left-hand side of the 

 illustration. The natural groove in the rachis is deepened by 

 the swelling of the sides, which may extend from one petiolule 

 to another, thus producing a labial formation. 



The gall is also figured by Theobald, "British Flies," p. 71 ; 

 Kerner, " Nat. Hist, of Plants," vol. ii., p. 534. 

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