Aug. 2, 1920.] Agricultural Gazette of N.S.W. 577 



Orchard and Garden Mites* " 



No. 1. Blister Mites (Family Eriophyidce.) 



W. W. FROGGATT, F.L.S., Government Entomologist. 



There are several groups of destructive little creatures known as mites. 

 Though not true insects, they are often serious pests in the garden and 

 orchard, where, on account of their rapid reproduction under favourable 

 climatic conditions and their small size, they may do a great deal of damage 

 before they are discovered. 



Mites belong to the A scirina. a well-defined group of the Arachnida, which 

 also includes spiders, scorpions, and ticks. They are distinguished from true 

 insects by the number and structure of their legs; while insects always have 

 three pairs, mites may have either three pairs or two. The head and thorax 

 of an insect are distinctly separated, and with the abdomen, form three 

 divisions, but the head and thorax of a mite are solidified together, and the 

 whole is known as the cephalothorax . 



Many species are cosmopolitan, and they have been spread far and 



wide in the leaf buds of their plant hosts or in the egg stage on the bark. 



They are divided into a number of well-defined families; of these, the blister 



mites and the spinning mites are well known to the gardener and 



orchardist. 



The Leaf Blister Mite {Family Eriophyidce). 



The members of this family are all so minute that they require to be studied 

 with a high-power microscope to obtain any details of their structure. They 

 bury themselves in the skin of the fruit, and either discolour and crack the 

 surface, produce a thickening of the tissue of the leaves, or form blister galls 

 or erineum, composed of masses of deformed hairs on the surface of the 

 leaves and known as acaro-cecidi. Banks has figured and described these 

 structures under the names dimple galls, pouch galls, capsule galls, nail 

 gal is, rib galls, and blister galls, according to their form. Several of our 

 eucalypts have their foliage thickly encrusted with patches of crimson 

 capsule galls, probably due to tlie presence of similar mites. Tn most of the 

 earlier works upon blister mites, they were placed in the genus Phytoptus^ 

 formed by Dujardin in 1851 ; but it has recently been discovered that 

 Siebold, working on the same group only a year before, had created the 

 genus Eriophyes for their reception ; so, by the recognised law of priority, 

 this name now displa-'es that of Phytoptus. 



From their curious, elongate fusiform shape and the fact th&t they only 

 had two pairs of legs, the entomologists who first discovered the makers of 

 the galls came to the conclusion that they were not adult, but some active, 

 eight-legged mite in the immature stage. It is quite a common thing to find 

 specimens of eight-legged mites sheltering on the under-surface of foliage 

 infested with blister mite, so it was not an unnatural mistake. 



