ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



41 



APPLE FRUIT MINER 



The serpentine or apple fruit miner {Marmara pomonella Busck) 

 is more of a curiosity than a pest. The adult is a very small moth, the 

 young of which form winding whitish mines just under the skin of the 

 apple (fig. 50). The mines are also occasionally found on prunes. 

 This insect occurs so rarely that control measures are not necessary. 



PEAR SLUG 



The pear slug (Eriocampoides limacina Retz.) feeds on the foliage 

 of pear and cherry trees, skeletonizing the leaves by eating the upper 

 surfaces (fig. 51). The 

 larvae are slimy and slug- 

 like in appearance, olive 

 green or almost black, 

 and about one half inch 

 long when full grown. 

 When they are numerous 

 the whole tree becomes 

 brown, as though swept 

 by fire. This should not 

 be allowed to happen to 

 valuable trees, as the re- 

 duction in the leaf surface 

 seriously interferes with 

 the growth of the fruit 

 and with the develop- 

 ment of fruit buds. _ This 

 insect is widely distrib- 

 uted in the United States, 

 having come in from 

 Europe. 



LIFE HISTORY 



The adult insects are 

 glossy black, 4-winged 

 flies, about one fifth inch 

 long. They are known 

 as sawnies because they 

 cut slits in the upper 

 surface of the leaves, in 

 which the eggs are laid. 

 The eggs in the leaves 

 have the appearance of 

 small blisters. The young 

 slugs hatch in a week or two and feed almost altogether on the upper 

 surface, usually avoiding any leaves that may have been attacked by 

 aphids or blister mites. Just after molting the slugs are yellow T , but 

 they soon secrete a slime w T hich gives them the characteristic olive 

 green or black color. Their bodies are somewhat enlarged in front 

 and taper behind. The slugs complete their growth in less than a 

 month, drop to the ground, and form cells in the soil, within which 

 they transform to adults in a couple of weeks. The second brood of 



Figure 49. — Work of apple leaf miner in apple lea/. 



