32 



FOREST ENTOMOLOGY 



become slightly flabby, they can then be very easily opened ; and if 

 examined under the microscope, the mites can be seen in great num- 

 bers. Fig. 33 is a representation of a single hawthorn leaf rolled by 

 this species. 



Eriophyes aucuparle (Con.) 



This species may be taken as a typical example of surface-injuries 

 to leaves by gall-mites. The leaves are injured on both sides, but 



the form of the leaf is 

 not injured. Examples 

 of this injury are very 

 common in Northumber- 

 land, but so far I have 

 not been fortunate enough 

 to see the mite under the 

 microscope. 



Fig. 34. 



Several other arboreal 

 species may be found ; 

 or, in other words, many 

 instances of malformation 

 on leaves, flowers, and 

 fruit may be recognised, 

 which on microscopical 

 examination w T ill show 

 Eriophyinse. Those mites, 

 however, may not always 

 be the direct cause of 

 the injuries referred to, 

 inasmuch as the primary 

 cause may be due to 

 minute parasitic fungi, 

 and the mites simply finding congenial association in the diseased 

 spots. Hence the enthusiastic student will find this dual nature of 

 parasitic disease a stimulus to encourage original investigation. 



Several other species may be found rolling the leaves of our forest 

 trees and shrubs, as, for example, the species forming rollings or 

 small galls on the edges of the leaves of blackthorn {Primus spinosa), 

 fig. 35. 



Fig. 34. Surface of leaflets of mountain-ash (Pjrus 

 aucuparia) injured by Eriophyes aucuparise. 



