THE TOBACCO SPLIT WORM. 6 



localities. The known range also includes Cuba, Costa Rica, Peru, 

 Hawaii, Australia, Tasmania, New Zealand, Sumatra, Transvaal, 

 Algeria, and southern Europe. 



COMMON NAMES. 



PJithorimaea operculella when working upon tobacco is known as 

 the tobacco splitworm and the tobacco leaf-miner; when working 

 upon potatoes it is known as the potato-tuber moth and the potato 

 moth. 



FOOD PLANTS. 



The known food plants of Plithorimaea operculetta include Solanum 

 torvum, S. verbascifolium, S. carolinense, S. nigrum{%), eggplant, 

 potato, tomato, Physalis peruviana, Physalis sp., Physalodes physa- 

 lodes, Datura stramonium, and tobacco. 



FOOD HABITS. 



The larva occurs as a borer and also as a leaf-miner. The former 

 is probably the original habit, examples of which have been ob- 

 served by Quaintance in .the fruit of eggplant, by Kotinsky in toma- 

 toes, and by C.-W. Howard and Oliff in the stems of tobacco. Dr. 

 L. R. De Bussy considers this the more common form of injury to 

 tobacco in Sumatra, where the larva forms a gall in the stem. C. W. 

 Howard reports a similar habit of the larva in the Transvaal. 1 



In Cuba and the United States the insect is known on tobacco as 

 a leaf-miner only. A boring tendency is still apparent, however, as 

 noted by Houser, in that the larva usually tunnels the midrib or a 

 vein in addition to mining the membrane of the leaf. In about 50 

 mines examined by us the larva had also tunneled the midrib or a 

 vein in almost every case. 



Only the older tobacco leaves are affected, unless the infestation 

 is very severe; and in these, the lower leaves, grayish, irregular 

 blotches are produced, which later turn brown and become fragile, 

 so that the tobacco is unfit for wrappers. At Clarksville, Tenn., 

 where the infestation is very slight, the larva in most cases begins 

 work in the "ruffles" along the midrib and may afterward migrate 

 and form mines in various parts of the leaf. 



In forming its mine the larva begins by spinning a tent of silk 

 between the midrib, or between the vein and the surface of the leaf. 

 Under this protection it soon forms a shelter between the leaf sur- 

 faces by consuming the parenchyma. The mined leaf becomes 

 more or less distorted, and this is especially noticeable on leaves, 



1 Gnorimoschema heliopa Low causes similar injury to tobacco in India, Ceylon, and Java. 



