88 BRITISH GALLS 



change their form as growth progresses. A remarkable 

 feature of these insects is the enormous amount of secretion 

 from their bodies. In some it is solid, as in Psylla buxi, 

 where it forms a very long string attached to the body ; in 

 others it is downy or waxy ; and in not a few it takes the 

 form of " honey dew," which is always so attractive to ants 

 and wasps. 



Psylla buxi attacks the apical shoots of the Box ; the leaves 

 become deformed and bent into a hemispherical gall resem- 

 bling a cabbage in miniature. Trioza rhamni causes shallow 

 depressions on the lower surface of Buckthorn leaves. 



A well-known Psyllid gall is that caused by Psyllopsisfraxini 

 on the leaves of the Common Ash. We found them in great 

 abundance in June, 1910, in the large wood above Weston- 

 super-Mare, and in the Ash plantations on the limestones in 

 other parts of Somerset. Usually only one-half of the leaf 

 is involved, generally towards the apex. The infected parts 

 assume a light yellow tint, and are traversed by swollen 

 reddish veins, presenting a pretty reticulated appearance. 

 In Plate XII., Fig. i («) shows a gall in an early state, (J) a 

 mature gall, (e) an old and broken one. Figs. 2 to 4 show 

 the Psyllid in various stages of development. 



The only insect gall that I am acquainted with on our 

 native Rushes is caused by the Psyllid Livia juncorum. It is 

 very distinctive. At maturity it resembles a tassel, and is 

 usually situated at the apex of the stem. It consists of a 

 variable number of stunted green blades springing from the 

 widened sheath of the shortened stem. The galls that are 

 in the blade are yellowish, but those which catch the sun- 

 light are beautifully tinted with red. They are not uncommon 

 on various species of Juncus on the margins of large ponds 

 in the southern counties— for instance, Frensham Pond, 

 in Surrey. 



We now come to the last family of the British gall-caus- 

 ing Homoptera — namely, the Coccidae. The minute insects 

 which comprise this family are popularly known as scale- 

 insects or mealy-bugs. All excrete matter which forms a 



