32 LEAF-MINING INSECTS 



Diptera, a round, seamless, tin box is used, a separate box 

 for each host plant and for each of the different types of mine 

 found on the same host plant. The proper records are 

 placed in the respective boxes. As a rule, the leaves remain 

 fresh in the boxes until the larvae have transformed. This 

 method requires a large number of boxes, and there is a 

 limit to the number that one can conveniently carry. There 

 is a more compact method. The leaves containing the 

 miners may be folded in tissue-paper triangles, much as 

 many entomologists use for duplicate material. These 

 small packages are then placed in a tin box. The box 

 retains enough moisture to prevent the leaves from drying 

 out, and leaves from many different plants may be placed 

 in the same box without confusing the records. If the 

 larvae transform before reaching the laboratory the pupar- 

 ium will be found within the envelope with their records. 



Ordinarily the larvae are not yet mature when they reach 

 the laboratory, and it is therefore necessary to allow them to 

 continue to feed. Larvae that naturally leave the wilted 

 leaves and enter the fresh ones are easy to rear, but those 

 that do not go to the fresh leaves are more difficult. Often 

 the leaves wither or decay before the larvae are full-grown. 



When the larvae transform they may be removed to small 

 vials by means of a camel's-hair brush. The vials are then 

 closed with cork stoppers in order to prevent evaporation 

 during the short period of pupation. When a larva trans- 

 forms within the leaf, the puparium is cut from the leaf 

 and allowed to dry for a few hours before the cork stopper 

 is placed in the vial. The pup aria are kept in these vials 

 until the adults emerge. The adults should be kept alive 

 for several days in order that they may attain their proper 

 color, since teneral specimens are practically indetermin- 

 able, especially among the Agromyzidae. Leaves bearing 

 mines may be preserved as herbarium specimens, mounted 

 on white cards, with the name of the family, the genus, and 



