42 



INSECTS INJURIOUS TO THE APPLE. 



brooded, the first brood hatching in May, the second in 

 September. 



As the oyster-shell bark-louse retains power of motion only 

 for a few days at most after hatching, it is mainly disseminated 

 to distant places by the distribution of young trees from infested 

 nurseries. In the orchard and its immediate neighborhood it 

 may be spread by being carried on the feet of birds, or attached 



FIG. 30. 



to the larger insects, or may be aided by the wind in passing 

 from tree to tree, while it is itself so brisk in its active state 

 that it can travel two or three inches in a minute, and hence 

 might in this way reach a point two or three rods distant be- 

 fore it would perish. Although this insect essentially belongs 

 to the apple-tree, it is frequently found on the pear, and 

 sometimes on the plum. 



Remedies. A species of mite (Fig. 31), Tyroglyphus mains 

 (Shinier), preys on the louse as well as on its eggs; and this 

 mite, so insignificant that it can scarcely be seen without a 

 magnify ing-glass, has probably done more to keep this or- 

 chard-pest within bounds than any other thing. 



Under the scales may sometimes be found a small active 

 larva devouring the eggs. This is the progeny of a small 

 four-winged parasite, belonging to the family Chalcididse, 

 named Aphelinus mytilaspidis Le Baron. In Fig. 32 we have 

 a representation of this insect highly magnified. 



