Galls caused by the larvae of Cecidomyia ulmarise 

 Bremi. 



on 



the leaf-segments of Spiraea Ulmaria Linn. 

 PLATE 89. 

 Synonymy of Insect. 



Cecidomyia uhnarice Theobald. 



Habitat of the Meadow-sweet. — This graceful and 

 attractive plant abounds in most parts of Britain on the 

 banks of streams, ditches, and ponds ; in meadows and 

 the corners of fields where damp. 



The Gall consists of a glabrous, hemispherical swelling on 

 the upper surface of the leaf-segment, continued as a 

 pubescent, recurvate, cone-shaped projection on the under 

 surface. 



Manner of Growth. — Gregarious ; frequently coalescent. 



Colour. — From pale green tinged with pink, to reddish brown 

 and dark brown. 



Average Dimensions of a Mature Specimen. 



Height above the surface of the leaf, 2 mm.; projection 

 below, 4 mm. 



May be sought during the months of June, July, and August. 



The Growth is complete by the end of July. 



The Typical Condition of the gall is unilocular. 



The Larva pupates in the gall. The imago emerges during 

 August. 



These galls coalesce to a remarkable degree ; as many as 

 eight will grow together, forming a large swelling on the upper 

 surface. The larval chambers, however, remain separate, and 

 the number of them may be determined by counting the cones 

 on the under surface. 



The gall is also figured by F. V. Theobald, " British Flies," 

 p. 71. 



2°9 14 



