CHAPTER XIV 

 Order Diptera 



The species of leaf-mining Diptera are comparatively 

 few in number. There are scarcely sixty known leaf -mining 

 species in America, and, while the inclusion of European 

 forms would increase the list, even with these the total of 

 known species is relatively small. Certain species are very 

 prolific and abundant. Some have a large number of host 

 plants, and can be found almost anywhere; while others are 

 rarer, and are limited to a few hosts or even to one. A few 

 species are so abundant that every leaf of their host plant 

 may become covered with mines. 



Most of the species have a general distribution throughout 

 the country, but there are some which are found only in a 

 limited area. The species may be divided generally into 

 eastern and western groups. Certain species are further 

 limited by the localization of the plants on which they occur. 

 Still other species appear to be restricted to certain patches 

 of plants, although the same species of plants are abundant 

 in other places in the near vicinity. 



Many of the species are European forms which have been 

 introduced into the United States and have not spread far 

 from their point of introduction. Boston, New York, and 

 Washington are the chief points in the East where species 

 have been introduced, and these are centers of infestation. 



The eggs. In the Anthomyiidae, the large and conspicu- 

 ous eggs are laid on the lower side of the leaf. The ovi- 

 positor, as might be expected, is very simple; there is no 

 need for specialization in such a method of egg-laying. In 

 the Trypetidae, the Agromyzidae, the Cecidomyiidae, and 

 Drosophilidae, the ovipositor is elongate and adapted for 



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