Galls caused by the larvae of Cecidomyia crataegi Wtz. 



on 



the leaves of Crataegus Oxyaoantha Linn. 



PLATE 79. 

 Synonymy of Insect. 

 T. oxyacanthcB Schk. 

 Cecidomyia cratcegi Theobald. 



Habitat of the Hawthorn. — This plant is so universally- 

 cultivated throughout Britain for the purpose of hedges 

 around fields and along roadsides, that no further descrip- 

 tion is necessary. 



The Gall is formed of a tuft of leaves situated at the 

 summit of an upright shoot growing out of the top of 

 the hedge. 



Manner of Growth. — One only on each shoot, although 



some of the other leaves may be affected. 

 Colour. — The leaves are the same colour as those not affected. 

 Average Dimensions of a Mature Specimen. 



Height, 20 mm.; girth, i8o mm. 

 May be sought during the months of June to October. 

 The Growth is complete by the end of September. 

 The Typical Condition of the gall is multilarval. 

 The Larv^ pupate in the ground. The imagines emerge 



during the spring. 



These ubiquitous clusters or rosettes of deformed sessile 

 leaves are familiar to all who travel along the country roads 

 during the summer. The number of leaves composing a rosette 

 may be as few as eight, or as many as forty. Each leaf is 

 thickly studded on both surfaces with short, thick, bluntly 

 pointed hairs. The leaflets in the centre of the cluster are 

 stunted in growth, curl inwards, and provide shelter and food 

 for the numerous larvae. 



The illustration is of specimens gathered at Hastings by 

 the author. 



190 



