THE ACARIXA OR MITES. 



137 



3. End piece of abdomen plainly separated Anthocoptes. 



End piece of abdomen not plainly separated Phyllocoples. 



4. Some of the dorsal abdominal rings extend backward spinelike on the side 



OxypleuTites. 



Dorsal rings not so , 5 



5. Dorsum of abdomen with two longitudinal furrows Epitrimerus. 



Dorsum without furrows Tegonotus. 



Most of the species, so far known from the United States, have been referred to 

 Eriophyes, but several of the other genera occur here. The most notable of all our 

 species is the pear-leaf blister mite, Eriophyes pyri Pagen- 

 stecher, an European species whose introduction into this 

 country seems to have been accomplished before 1870. It 

 is now widely distributed throughout the pear-growing re- 

 gion, and also occurs in Australia. It appears to be more 

 injurious in this country than in Europe, and in some 

 cases it is so abundant that the tree sheds nearly all its 

 leaves before the fruit is ripe. The mites pass the winter 

 in the buds, and begin to feed before the leaves are un- 

 rolled. They form red blister like spots nearly one-fourth 

 inch across. These spots become green by June, and then 

 turn brown, and the tissue becomes hard and corky. The 

 opening is on the under side. As mites often start galls close 

 together, they soon coalesce and form large blotches. 

 Prof. Slingerland has found that they can be practically 

 exterminated by spraying the trees in winter with kerosene 

 emulsion diluted with from 5 to 7 parts of water. This 

 mixture reaches the hibernating mites in the buds and 

 kills them there. The pear-leaf blister mite also occurs on 

 apple leaves. The galls often contain other species of mites, 

 three of which, Phyllocoptes schlechtendali Nalepa, Epitrimerus piri Nalepa, and Erio- 

 phyes malifoliae Parrott, have been found in these galls in our country. 



Another species of considerable economic importance is Phyllocoptes oleivorus Ash- 

 mead, the rust mite of the orange and the silver mite of the lemon. It occurs in Florida 

 and California and lives on both leaves and fruit. On the foliage the mite causes the 

 leaves to become curled and lose their gloss. On the fruit of the orange the mite 

 produces a hardening of the rind, which becomes bro^vnish in color. The infested 

 orange, although injured in appearance, is better able to stand long shipment and is 

 more juicy than the clean fruit. Upon the lemon the mites cause the rind to become 

 whitened or silvered. The fruit is better for shipment, but the rind is injured for 



commercial purposes. The spherical eggs 

 are deposited on the leaf or fruit, generally 

 in clusters. They hatch in 5 to 10 days. 

 It takes about 2 weeks to reach maturity. 

 Its food is the essential oil, found in the epi- 

 dermal cells. Mr. Hubbard, who studied 

 this mite more carefully than anyone else, 

 estimated that there may be 75,000 mites and eggs on a single leaf. The best remedy 

 is flowers of sulphur, which may be applied dry or mixed in with a spray solution, 

 as kerosene emulsion. 



Another Phyllocoptes, P. schlechtendali Nalepa (fig. 290), is of economi.c importance, 

 as it often occurs on pear, blackening and curling the leaves. It also occurs on other 

 kinds of fruit trees. It is larger and much broader than the pear-leaf blister mite. 



Phyllocoptes amygdalina Banks occurs on the leaves of Davids peach in California, 

 and another species, P. calif omica Hall, has been found on the leaves of Artemisia. 



Fig. 286.— Rib galls of an 

 Eriophyes. (Author's 

 illustration.) 



T — I ~r 

 ,— Section of an erineum on leaf. 

 (Author's illustration.) 



