160 LEAF-MINING INSECTS 



larva pupates in a slight but somewhat tough cocoon of silk and 

 debris among clods or rubbish at or near the surface of the soil. 



The pupa is yellowish brown, 5.5 to 7 mm. long and 1.5 to 2 

 mm. broad; it is broadest through the metathorax, tapering both 

 anteriorly and posteriorly. The abdomen, excepting the last 

 three segments, is set with very minute spinules; it bears at the 

 tip mid-dorsally a short, curved, erect, pointed horn flanked by 

 about four pairs of long hooked spinules. Each abominal seg- 

 ment is set with a transverse row of spinules near the anterior 

 margin. 



The moth is slender, inconspicuous, with dark grayish wings 

 bearing indefinite yellowish streaks and having an expanse of 

 about 20 mm. 



At Clarksville, Tennessee, the splitworm requires 25 to 30 days 

 in summer for completing its development from egg to adult. Of 

 this time 4 are spent in the egg stage, 15 to 17 in the larval stage 

 and 6 to 9 days in the pupal stage. 



The egg-plant leaf-miner, P. glochinella, is another species 

 of this genus that mines the leaves of some of the same kinds 

 of plants. It is distinguished by its habit of constructing 

 within the mine a dense silken frass-covered tube. Jones 



(23) says: 



The mines in egg-plant and Solarium carolinense are always 

 along the edge of the leaf. A number of larvae sometimes work 

 in a single leaf and at least two have been found using what were 

 apparently parts of the same mine. The mined portion of the 

 leaf has the appearance of a dry, oftentimes puffy blotch, the 

 older mined area being dead and brown. The leaf becomes dis- 

 torted about the mine and sometimes curls over it, but no silk is 

 apparent on the leaf surface. The larva removes the parenchyma 

 and constructs a firm silken tube, in which it is often found, within 

 the mined area. 



In its larval habits Phthorimaea glochinella apparently differs 

 from P. operculella in that it feeds entirely within the leaf, not 

 leaving the mine to roll the leaf or feed on other portions of the 

 plant. The fact that the mines seem invariably to be made along 

 the edge of the leaf is also a habit not shown by operculella. 



