44 



MANUAL OF VEGETABLE-GARDEN INSECTS 



Th 



(' iff! ported tuniij) Icaj'-iiiiucr, Scaptoni.yrid Jlarrold jNIeigen 



Originally a native of Europe where it is known as the turnip 

 leaf-miner, this insect was introduced into the United States 

 some time before 1891, and is now widel,y distributed, ranging 



from Alaska to New Hampshire 

 and south to Kentucky and 

 Virginia. 



Very little is known concerning 

 its early seasonal history and 

 the number of broods occurring 

 annually has not been deter- 

 mined. The parent fly ap- 

 parently deposits her eggs on 

 the upper surface of the leaves. 

 On hatching, the young maggot 

 burrows into the leaf and feeds 

 just below the upper epidermis, 

 producing at first an irregular 

 tortuous burrow which is sud- 

 denly widened to form a large 

 blotch. The epidermis over the 

 mine turns whitish and by a 

 coalescence of several mines the 

 A young cabbage leaf whole leaf may take on this 

 color (Fig. 37). The full-grown 

 maggot is about i inch in length, 

 whitish in color and cylindrical in form, tapering towards the 

 head and bluntly truncate behind. When mature the larval 

 skin hardens and turns reddish brown to form the puparium 

 within which the true pupa is to be found. This trans- 

 formation may take place in the mines but usually the puparia 

 are found under rubbish on the surface of the ground. In 

 Kentucky the flies have been observed to emerge in late 



Fig. 37. 



showing the work of the imported 

 turnip leaf-miner. 



