attack. As a general statement, it may be said that the insect will be 

 most destructive to summer and fall varieties, or to those varieties 

 which are ripe or are approaching maturity during the period of 

 principal activity of the flies. 



HOW THE INSECT SPREADS. 



It is not known whether the apple maggot has spread from the 

 New England States, where its injuries were first noticed, to the sev- 

 eral localities w^here its presence has been observed — as in Ohio, Wis- 

 consin, Michigan, North Carolina, etc. — or whether the insect, al- 

 ready present on haws, simply turned its attention to apples. The 

 former view, however, appears the more probable, and its spread 

 would have been readily brought about by the introduction of in- 

 fested apples. In regions where the insect occurs in apples, a con- 

 siderable amount of infested fruit wnll be barreled, the larvic later 

 deserting the fruit and forming puparia on the bottom of the barrel. 

 In the ordinary course of commerce the insect would thus be intro- 

 duced into new localities, often quite remote. In view of the extent 

 of apple production in the territory which has long been infested 

 with this species (i. e., the New England States), and the consequent 

 almost certain dissemination of the apple maggot to various parts of 

 the country, it is cause for much surprise that the insect is not much 

 more generally and widely established as an apple pest. It is very 

 probable that the insect has been introduced into most of the apple- 

 growing regions in the United States and also into those of Europe 

 and the Colonies, but for some reason has not established itself. 

 Thus the insect has been frequently found in apples on the markets in 

 Washington, D. C, though there is no evidence to indicate that it 

 has become established in orchards in that vicinity. 



When once established in an orchard, its spread fortunately is 

 usually very slow. It may confine its attack to a single tree, for two 

 or three years, before spreading to adjacent trees of the same or 

 other varieties equally subject to attack; and varieties seriously in- 

 fested in one orchard may be exempt in another. The slowness of 

 its spread from tree to tree and from one orchard to another has been 

 commented upon by numerous workers. 



The flies in their habits are exceedingly local, apparently confining 

 their attention to the trees upon wdiich the previous generation devel- 

 oped — in marked distinction to the spreading habits of many other 

 insects. This habit is a very fortunate one for the fruit grower, and 

 is of much practical importance in control, permitting great reduc- 

 tion and possible extermination of the pests when infestation is lim- 

 ited to but a few trees, and especially in localities but recently 

 invaded. 



[Cir. 101] 



