INSECTS INJURIOUS TO THE APPLE AND PEAR 



529 



distributed on nursery trees. Only young trees are usually much in- 

 jured by this and the following 

 species of aphids, old trees 

 rarely being injured, except 

 that where the aphids are ex- 

 cessively abundant they 

 sometimes injure the young 

 fruit, causing it to become 

 stunted and misshapen. The 

 foliage of young trees soon be- 

 comes covered with the ver- 

 min, which feed on the under 

 surfaces of the leaves, caus- 

 ing them to curl up and then 

 drop. This curling of the 

 foliage is more commonly 

 caused by this species than 

 any other, though the rosy 

 apple-aphis has a similar ef- 

 fect. The aphids secret the 



sweet honey-dew very pro- FlG . 457 ._s tages of the ap pie- ap his, 

 fusely and so attract large pomi. After Baker, U. S. Dept. of Agr. 

 numbers of ants, which feed upon it. The ants are always found 

 associated with them, and the presence of numerous ants on a tree 



FIG. 458. The apple-aphis, winged viviparous female greatly enlarged, 

 is a good indication of aphids. The honey-dew soon covers badly 



