204 



Journal of Agriciiltiire. 



[ii April, 1910. 



conceit was turned into a spider. This class {Arachnida) includes scorpions,, 

 spiders, ticks and mites. The two latter form, an order of their own (Acari). 

 Both are of more than a passing interest to the agriculturalist because they 

 provide a large number of the animal and vegetable parasites with which 

 he has to cope, and which eventually, if unchecked, will drain his pocket. 

 The ticks furnish well known examples in the cattle and poultry ticks and 

 many others, while poultry fanciers and dog breeders are often troubled 

 with tiny parasitic mites. Of the mites that attack plants, the red spider 

 is unfortunately too well known to the fruit-grower and gardener, both 

 professional and amateur. Another representative of the mites was verv 

 much in e\idence in the vineyards of the Rutherglen and other districts 

 in 1899. Vine canes and even parts of the vine stakes were red with the 

 eggs of this mite {Bryobia fratensis), which is considerablv larger than the 

 red spider. However, since the season mentioned, this pest has not been 

 seen in any alarming numbers in the Rutherglen district. 



acarid causing erino.se. 

 (after vial a). 



«»<a®>'^»A.AA^0(?l 



ACARIDS AMONG HAIRS ON UNDER 

 SURFACE OF LEAF (AFTER FOEx). 



The group to which the acarid causing Erinose l>elongs includes the 

 vermiform or worm-shaped mites. One family of the latter is an animal 

 parasite, but the gall-mites, with which we are alone now concerned, live 

 exclusively on vegetation. Apparently, they have no eyes, and no special 

 breathfng organs known as tracheae, but breathe through the skin (Pocock). 

 They are provided with piercing organs with which they attack the foliage 

 or buds. Normally, the Arachnida have four pairs of legs. This provides 

 a rough and ready way of distinguishing them on the one hand from true 

 insects, which have three pairs, and crustaceans on the other, which are 

 provided with fiye pairs of legs. However, the Phytofiidcc, or, as they 

 are now more generally called, Eriophyidce, have apparently lost all trace 

 of the third and fourth pairs of legs. They have " only two pairs of legs 

 which have no claws, but are furnished with bri.stles and ' feather hairs ' " 

 (Warburton). Their structure will be readilv seen and understood from the 

 accompanying figures drawn ])v Mr. Brittlebank after Viala and Fciex. 



They are known as Gall or Blister mites from their work on the leaves, 

 buds or twigs. The scientific names Phytoptus-Eriophyes are in allusion 

 to the bli-stered or scorched appearance of the affected leaves and to the 

 woolly appearance exhibited by the attacked plants. About 200 species 

 have been recorded, and each seems to favour a special kind of tree or 

 plant. Careful observers of the more injurious kinds afiirm that they are 

 spread by means of insects, spiders, &c. Even the aphis has been credited 

 with providing a frequent and ready means of tran.sit for some species. 



