Galls caused by the larvae of Cecidomyia lathyri Felfld. 



on 



the terminal leaves of Lathyrus pratensis Linn. 

 PLATE 80. 

 Synonymy of Insect. 



Cecidomyia lathyri Theobald. 



Habitat of the Meadow-pea.— Abundant throughout 

 Britain in fields, moist meadows, on hedge-banks, and 

 similar situations. 



The Gall is formed by the larvae causing the terminal 

 leaves to meet along their edges and enclose the unex- 

 panded leaves. 



Position. — At the top of the stem. 



Manner of Growth.— Several on a stem ; glabrous. 



Colour. — Pale green, yellowish green. 



Average Dimensions of a Mature Specimen. 

 Height, 20 mm. ; breadth, 8 mm. ; girth, 20 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 multilarval. 



The Larv.« pupate in the gall and in the earth. The 

 imagines emerge during the spring. 



The disturbance caused to the plant-tissue by the larvas 

 causes the uppermost pair of e.xpanded leaves to meet along 

 the edges with their upper surfaces inwards, and form a kind 

 of closed bag, the basal half of which becomes considerably 

 swollen, the upper half remaining flat. Within the swollen base 

 the young leaves cluster, and are prevented from expanding 

 by the tightly closed edges of the outer leaves, and the feeding 

 of the larva; upon their tissues. 



The illustration is of specimens gathered at Hastings by the 

 author. 



192 



