Galls caused by the larva- of Geoidomyia urtiC8B Ferris. 



on 



the leaves of Urtica dioica Linn. 

 PLATE 90. 



Synonymy of Insect. 



Cecidoniyia urticce Theobald. 



Hahitat of the Common Nettle.— Common and abundant 

 throughout Britain by the roadside, waste places, along 

 hedges, corners of fields and meadows, neglected orchards, 

 etc. 



The Gall is FOKMKIJ by the accumulation of sap around the 

 ovum, which continues for some time after the hatching of 

 the larva. 



Position.— On all parts of the stem, leaves, petioles, flower- 

 stalks, and flower-clusters. 



Manner of Growth. — .Singly, and gregarious ; irregular- 

 shaped. 



Colour. — Very pale green, .some a pale yellow. 



AvERACE Dimensions of a Mature Specimen (situated in 

 the blade of the leaf, and more or less globular in 

 outline). 

 Diameter, 5 mm. 



May I!E sought during the months of May to December. 



The Growth is complete by the end of November. 



The Typical Condition of the gall is unilocular. 



The Larva pupates in the ground. The imago emerges 

 during the spring. 



These galls vary in size and shape according to the part of 

 the plant they affect. Those on the blade of the leaf are small 

 and globular, with about equal proportions on both surfaces of 

 the leaf; those close to the petiole distend the lower surface 

 only, and are often much larger and very irregular in outline. 

 The axillary leaflets are often swollen into small pear-shaped 

 masses. The petioles of the leaves frequently show bulbous 

 swellings, while the flowers and their stalks have many small 

 pea-shaped galls on them. 



