THE PEAR PHYTOPTUS. 119 



CHAPTER XIX. 



THE PEAR PHYTOPTUS. 



(Phytoptus pyri.) 



Order: Arachnoidea. Family: Acarince. Sub-Family: Phytoptidce. 



Orchardists and others who are familiar with pear- 

 growing will have observed the leaves of the pear tree to be 

 partly covered with greenish -brown blister-like looking 

 blotches (see Plate XIV., Fig. 1), rendering the trees very 

 unsightly arid causing them to prematurely shed their 

 leaves, to the undoubted detriment of both the tree and 

 its fruit. 



This damage, then, is caused by a tiny insect belonging 

 to the family phytoptidce, or gall Mites, a group of insects 

 which includes also in its ranks the well-known Eed 

 Spider of our gardens and conservatories. 



" On examining a pear leaf," as Mr. Crawford* remarks, 

 "that has been attacked some little time, a number of 

 brown blister-looking spots will be seen. These are at 

 first nearly round, but as they grow in size they spread 

 laterally, generally taking the direction of the venation of 

 the leaf. These are galls, for there is a decided thicken- 

 ing of the' inside portion of the leaf, and each of these 

 contains a greater or less number of these Mites (see 

 Plate XIV., Fig. 2), which have been magnified and drawn 

 from nature. As the phytopti suck away the juices of the 

 .leaf, or otherwise destroy the cellular tissue, it turns 

 brown, and finally nearly black, but beyond stimulating 

 the tissue so that it is developed abnormally, as in the case 

 of all gall-producing insects, it does not appear to do 

 further injury. As the galls enlarge, owing to the food 

 requirements of the population within, they often coalesce, 

 so that in time the greater portion of the leaf becomes a 

 blackish scab, containing probably one thousand phytopti" 



* Report on the Fusicladiums, p. 46. 



