APPLE INSECTS 



175 



Fig. 173. 



Oyster-shell scales turned over to show 

 eggs. 



infested, but occasionally a few of the scales develop on the 

 fruit even in the North, where there is })ut a single generation 

 annually. 



The oyster-shell 

 scale is beset by 

 many natural ene- 

 mies. Some of the 

 ladybird beetles, the 

 twice-stabbed lady- 

 bird especially, de- 

 vour many, and th(^ 

 eggs beneath the 

 scales are preyed 

 upon and often a 

 large proportion of 

 them, 50 to 75 per 

 cent in some cases, 

 eaten by a mite, Hemisarcoptes coccisugus, in France, and 

 in America by the larvae of at least five minute parasites, 

 Aphelinus mytilaspidis, ahnormis, and fuscipennis, Anaphes 

 gracilis, and Chiloneurus diaspidinarum. These parasites 



emerge through pin-like holes in the 

 scales and often a majority of the 

 scales on a tree show these holes. 

 It usually requires two of the para- 

 sitic larvae to destroy all the eggs 

 under a scale, one larva often leaving 

 from 2 to 20 eggs. A few birds, the 

 brown creeper, black-capped chicka- 

 dee and white-breasted nuthatch, are 

 also reported as feeding on it. The 

 combined efforts of all these natural enemies often prevent 

 serious injury by the oyster-shell scale and occasionally nearly 

 exterminate it in a locality. 



Fig. 174. — Apple infested 

 with oyster-shell scales. 



