19 



CHAPTER I. 



EEIOPHYID^ (Phytoptid.e) ok GALL-MITES. 



The Eriophyiclae, or gall-mites, are so small in size (being only visible 

 when viewed under a very strong pocket lens or microscope) that we 

 can only recognise them in the forest through the medium of their 

 injuries. In other words, being practically invisible, the young student 

 in forest entomology cannot associate the creature with its injuries, as 

 in the case of most insects ; and further, as the injuries caused by 

 those creatures are in appearance so closely allied to the damage done 

 by many species , of parasitic fungi, the beginner may either overlook 

 or misunderstand them. Perhaps, therefore, the best method of 

 commencing the study of this group of arboreal mites is through 

 the medium of a common horticultural species — viz., the currant-bud 

 mite. In fact, it may be truly said that the study of gall-mites 

 in tliis country has received special attention on account of the 

 species on black currant having become a common garden pest in 

 many parts of the country. The general appearance of this pest is 

 only too easily recognised by the swollen buds, known in some 

 localities by the graphic term "blind bud." The creature causing 

 this widespread trouble has long been known by the name of 

 Plujtoptus rihis (Westw.) 



The common garden pest referred to has its equivalent in the 

 forest, producing "blind buds" and other abnormal growths on 

 several kinds of trees. The latter may be various forms of galls on 

 the leaves, rollings of leaves, or deformation of flower and fruit, &c. 



The abnormal growths arising from the action of gall-mites were at 



one time considered by botanists as a species of micro-fungi, and 



termed " Erineum." Frank gives a very interesting account of those 



abnormal hairs on the leaves,^ which are either caused by the gall- 



^ Die Krankheiten der Pflanzen, Bd. iii. 1896. 



