232 LEAF-MINING INSECTS 



making holes and inserting the eggs in the leaves of the host. 

 An unusually long ovipositor is found in a European form, 

 Phytomyza varipes Meig., it being in this species as long as 

 the abdomen. 



The larvae. The larvae of the leaf-mining Diptera are 

 very diverse. The more primitive forms are members of 

 such families as the Tipulidae, and the Chironomidae, 

 whose larvae have a definite head, with mandibles, maxillae, 

 eyes, and antennae. The body is composed of a head, a 

 thorax, and ten abdominal segments. The larvae of the 

 leaf-mining species of these families resemble the free rang- 

 ing forms in that they have a head of some sort, and mouth 

 parts, but they differ in that they lack posterior breathing 

 tubes, suckers, spines, and hairs. The projecting parts are 

 reduced to a minimum. They show a reduction of protrud- 

 ing parts fitting them to their environment. 



The larvae of the specialized families of leaf -miners, as 

 the Anthomyiidae, the Trypetidae, the Drosophilidae, and 

 the Agromyzidae, differ very little in structure from the 

 larvae with other habits in these families. They are all 

 highly specialized, with no head-capsule, mandibles, nor 

 maxillae. The normal mouth parts are replaced by the 

 pharyngeal skeleton. The antennae are reduced to minute, 

 one-segmented appendages, and the eyes are absent. In 

 certain of the leaf-mining families, the ambulatory setae 

 are prominent structures. 



The mines. The various kinds of mines produced by the 

 Diptera can be classified under three types — linear, linear- 

 blotch, and blotch. The long, narrow, and tortuous linear 

 mines are undoubtedly the primitive type, and they occur 

 chiefly in the primitive families, as Tipulidae. Only an 

 occasional linear mine is found in the specialized family 

 Agromyzidae, and none are found in the Anthomiidae. All 

 blotch mines have their origin in a linear mine. As the 

 larva enlarges its mine to form a blotch, the primary linear 



