ORDER LEPIDOPTERA 65 



for it is obviously impossible to get much nourishment from 

 sap and still leave anything particularly solid in the ex- 

 crement. 



The mines of Nepticulae begin as slender galleries and 

 often continue so until the end but these are readily dis- 

 tinguishable from the linear mines of Phyllocnistis. Neptic- 

 ulae are tissue feeders and tunnel out much parenchyma, 

 thus leaving the mined area more transparent than the 

 remainder of the leaf. There is very much more body to the 

 excrement. Sometimes Nepticula mines widen out into a 

 blotch and this widening may be quite abrupt, synchronous 

 with the last larval moult. 



Members of the genus Bucculatrix make narrow winding 

 galleries; but because they become external feeders early in 

 their life history their mines may be recognized by their 

 shortness especially if small scars halfway through the leaf 

 show where they have fed externally. 



Of the blotch mines, the mines of Tischeria usually start 

 as a narrow channel but almost at once they begin to widen 

 and presently spread out as a great blotch. Certain of 

 them that widen out and gradually to a flaring edge have 

 been called trumpet mines. They are rather unique in 

 being carpeted throughout with silk. 



While the mouthparts of the Lithocolletis larva are 

 adapted for sap-feeding it shears loose the epidermis over the 

 whole territory of its mine. When at the third moult it 

 acquires tissue-feeding mouthparts it goes over the same 

 area again this time carefully stripping the mesh of veins 

 of all parenchyma. With these mouthparts comes also the 

 ability to spin silk, an ability which some of them employ 

 in making their quarters more roomy in keeping with their 

 now cylindrical form. They spin the silk back and forth 

 over the loosened cuticle of the leaf and this silk in drying 

 shrinks, drawing the cuticle into folds. The other thicker 

 side arches in proportion and the erstwhile flat mine is con- 



